From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8652123B8 for ; Wed, 20 Dec 2023 00:19:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="JPTksi+1" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-5c1b986082dso147474a12.0 for ; Tue, 19 Dec 2023 16:19:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031545; x=1703636345; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=NUHnww5ktcUEm6gbdUuCZMr5JgxeUPAZP1Uwwm4gSJs=; b=JPTksi+1QkpwIp9mYQ42y/GKuFXCfknzAretgW5L6UmlJPxOJIOL0VN+vdKY4nxSKS f1GbT4A9g7hZNUnkn8IKsEWFvhw7WYQtE5SXPgbq9vFPHRoHuKpjjl1poFKG000EcSXV g1N1nBZTfDleN4xBL4n6P2WdBH+XpSg388RjD6w5TiOV2ZiuXSpXRy/x22lInm4iIVbM 1s8qAxjZANGOs3Yd/e4nNgQFu2cQD4O0NJspVoWypSmZhQBAS6Y69ohXpzWEZ2g6c9OC 3zWqA8hRuN14BcZVDc0Dhbo/nlo4L0Xhv8v5Z36CJG3fgJPKiDBg5T2ku8h0D0TcMYCs 9qow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031545; x=1703636345; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NUHnww5ktcUEm6gbdUuCZMr5JgxeUPAZP1Uwwm4gSJs=; b=tIUSEbxI9Fl+2y+ZBnAHPGpDUfz+4GinBCQnEr9pAmT7iclZIu9qswUqjcp4HQlb/a 1ExLsrrU3g8ttap/bPmLOH4vjPZ5qlBROYuNYHZdjBWFoFZ/n82fpHqtF2rt0rJ2I1zc zLER9WoUGR+1MDOFCyM4sq9GsFBWlU6G1OcKXNMPFPCMo6z1lMpSojtTEAPOb9HXLjAj CWx85YeCfmLRxFcvOlscmd9PUOO30Xy7msXzAq84svzyx3FtHqcHzyu8SI3hNeIpZkh3 G3r+79gJ+PwcwHWe3AbxzxpUB6Mmpt0Ud2D1mQY6STbI1BTcmcFHJzDsLdNDxgVsKUjr ubLg== X-Gm-Message-State: AOJu0Yx9c2cghaR0EhuvjlsTFa2mrBmBGX9Y5B0FvJ2XQ1Q1MT1ncU8s JaX1zuEGyCKJ5PC3jUgF3ZHZwEk/TMrcBhmFG+Xp1DRB4PQWe1DHyie3UdHsm4uOdrpGGpeGFQR y7C8piCYBdVBtXKgM0TvZsqJzBle4LYTBQMx3820sIgiVDC+A0opv71Xh8kpWskuuwQzJ+Oo= X-Google-Smtp-Source: AGHT+IGo5rlZ2EWtcahUdEV5X1N/1i4O/tPYFCTuxXZMdv3cH1dn2fb15eyFgZxhI9LlgzkQX2rpajQ9NpOr X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6a02:6a1:b0:5cd:9acb:a4a2 with SMTP id ca33-20020a056a0206a100b005cd9acba4a2mr42196pgb.2.1703031543770; Tue, 19 Dec 2023 16:19:03 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:12 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-2-jstultz@google.com> Subject: [PATCH v7 01/23] sched: Unify runtime accounting across classes From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra All classes use sched_entity::exec_start to track runtime and have copies of the exact same code around to compute runtime. Collapse all that. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) [fix conflicts, fold in update_current_exec_runtime] Signed-off-by: Connor O'Brien [jstultz: rebased, resolving minor conflicts] Signed-off-by: John Stultz --- v7: * Minor typo fixup suggested by Metin Kaya --- include/linux/sched.h | 2 +- kernel/sched/deadline.c | 13 +++------- kernel/sched/fair.c | 56 ++++++++++++++++++++++++++++++---------- kernel/sched/rt.c | 13 +++------- kernel/sched/sched.h | 12 ++------- kernel/sched/stop_task.c | 13 +--------- 6 files changed, 52 insertions(+), 57 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 292c31697248..1e80c330f755 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -523,7 +523,7 @@ struct sched_statistics { u64 block_max; s64 sum_block_runtime; =20 - u64 exec_max; + s64 exec_max; u64 slice_max; =20 u64 nr_migrations_cold; diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index b28114478b82..6140f1f51da1 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1275,9 +1275,8 @@ static void update_curr_dl(struct rq *rq) { struct task_struct *curr =3D rq->curr; struct sched_dl_entity *dl_se =3D &curr->dl; - u64 delta_exec, scaled_delta_exec; + s64 delta_exec, scaled_delta_exec; int cpu =3D cpu_of(rq); - u64 now; =20 if (!dl_task(curr) || !on_dl_rq(dl_se)) return; @@ -1290,21 +1289,15 @@ static void update_curr_dl(struct rq *rq) * natural solution, but the full ramifications of this * approach need further study. */ - now =3D rq_clock_task(rq); - delta_exec =3D now - curr->se.exec_start; - if (unlikely((s64)delta_exec <=3D 0)) { + delta_exec =3D update_curr_common(rq); + if (unlikely(delta_exec <=3D 0)) { if (unlikely(dl_se->dl_yielded)) goto throttle; return; } =20 - schedstat_set(curr->stats.exec_max, - max(curr->stats.exec_max, delta_exec)); - trace_sched_stat_runtime(curr, delta_exec, 0); =20 - update_current_exec_runtime(curr, now, delta_exec); - if (dl_entity_is_special(dl_se)) return; =20 diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d7a3c63a2171..1251fd01a555 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1129,23 +1129,17 @@ static void update_tg_load_avg(struct cfs_rq *cfs_r= q) } #endif /* CONFIG_SMP */ =20 -/* - * Update the current task's runtime statistics. - */ -static void update_curr(struct cfs_rq *cfs_rq) +static s64 update_curr_se(struct rq *rq, struct sched_entity *curr) { - struct sched_entity *curr =3D cfs_rq->curr; - u64 now =3D rq_clock_task(rq_of(cfs_rq)); - u64 delta_exec; - - if (unlikely(!curr)) - return; + u64 now =3D rq_clock_task(rq); + s64 delta_exec; =20 delta_exec =3D now - curr->exec_start; - if (unlikely((s64)delta_exec <=3D 0)) - return; + if (unlikely(delta_exec <=3D 0)) + return delta_exec; =20 curr->exec_start =3D now; + curr->sum_exec_runtime +=3D delta_exec; =20 if (schedstat_enabled()) { struct sched_statistics *stats; @@ -1155,9 +1149,43 @@ static void update_curr(struct cfs_rq *cfs_rq) max(delta_exec, stats->exec_max)); } =20 - curr->sum_exec_runtime +=3D delta_exec; - schedstat_add(cfs_rq->exec_clock, delta_exec); + return delta_exec; +} + +/* + * Used by other classes to account runtime. + */ +s64 update_curr_common(struct rq *rq) +{ + struct task_struct *curr =3D rq->curr; + s64 delta_exec; =20 + delta_exec =3D update_curr_se(rq, &curr->se); + if (unlikely(delta_exec <=3D 0)) + return delta_exec; + + account_group_exec_runtime(curr, delta_exec); + cgroup_account_cputime(curr, delta_exec); + + return delta_exec; +} + +/* + * Update the current task's runtime statistics. + */ +static void update_curr(struct cfs_rq *cfs_rq) +{ + struct sched_entity *curr =3D cfs_rq->curr; + s64 delta_exec; + + if (unlikely(!curr)) + return; + + delta_exec =3D update_curr_se(rq_of(cfs_rq), curr); + if (unlikely(delta_exec <=3D 0)) + return; + + schedstat_add(cfs_rq->exec_clock, delta_exec); curr->vruntime +=3D calc_delta_fair(delta_exec, curr); update_deadline(cfs_rq, curr); update_min_vruntime(cfs_rq); diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 6aaf0a3d6081..9cdea3ea47da 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1002,24 +1002,17 @@ static void update_curr_rt(struct rq *rq) { struct task_struct *curr =3D rq->curr; struct sched_rt_entity *rt_se =3D &curr->rt; - u64 delta_exec; - u64 now; + s64 delta_exec; =20 if (curr->sched_class !=3D &rt_sched_class) return; =20 - now =3D rq_clock_task(rq); - delta_exec =3D now - curr->se.exec_start; - if (unlikely((s64)delta_exec <=3D 0)) + delta_exec =3D update_curr_common(rq); + if (unlikely(delta_exec < 0)) return; =20 - schedstat_set(curr->stats.exec_max, - max(curr->stats.exec_max, delta_exec)); - trace_sched_stat_runtime(curr, delta_exec, 0); =20 - update_current_exec_runtime(curr, now, delta_exec); - if (!rt_bandwidth_enabled()) return; =20 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 2e5a95486a42..3e0e4fc8734b 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2212,6 +2212,8 @@ struct affinity_context { unsigned int flags; }; =20 +extern s64 update_curr_common(struct rq *rq); + struct sched_class { =20 #ifdef CONFIG_UCLAMP_TASK @@ -3261,16 +3263,6 @@ extern int sched_dynamic_mode(const char *str); extern void sched_dynamic_update(int mode); #endif =20 -static inline void update_current_exec_runtime(struct task_struct *curr, - u64 now, u64 delta_exec) -{ - curr->se.sum_exec_runtime +=3D delta_exec; - account_group_exec_runtime(curr, delta_exec); - - curr->se.exec_start =3D now; - cgroup_account_cputime(curr, delta_exec); -} - #ifdef CONFIG_SCHED_MM_CID =20 #define SCHED_MM_CID_PERIOD_NS (100ULL * 1000000) /* 100ms */ diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index 6cf7304e6449..b1b8fe61c532 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -70,18 +70,7 @@ static void yield_task_stop(struct rq *rq) =20 static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) { - struct task_struct *curr =3D rq->curr; - u64 now, delta_exec; - - now =3D rq_clock_task(rq); - delta_exec =3D now - curr->se.exec_start; - if (unlikely((s64)delta_exec < 0)) - delta_exec =3D 0; - - schedstat_set(curr->stats.exec_max, - max(curr->stats.exec_max, delta_exec)); - - update_current_exec_runtime(curr, now, delta_exec); + update_curr_common(rq); } =20 /* --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 21C6633C1 for ; 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Tue, 19 Dec 2023 16:19:05 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:13 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-3-jstultz@google.com> Subject: [PATCH v7 02/23] locking/mutex: Remove wakeups from under mutex::wait_lock From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In preparation to nest mutex::wait_lock under rq::lock we need to remove wakeups from under it. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) [Heavily changed after 55f036ca7e74 ("locking: WW mutex cleanup") and 08295b3b5bee ("locking: Implement an algorithm choice for Wound-Wait mutexes")] Signed-off-by: Juri Lelli [jstultz: rebased to mainline, added extra wake_up_q & init to avoid hangs, similar to Connor's rework of this patch] Signed-off-by: John Stultz --- v5: * Reverted back to an earlier version of this patch to undo the change that kept the wake_q in the ctx structure, as that broke the rule that the wake_q must always be on the stack, as its not safe for concurrency. v6: * Made tweaks suggested by Waiman Long v7: * Fixups to pass wake_qs down for PREEMPT_RT logic --- kernel/locking/mutex.c | 17 +++++++++++++---- kernel/locking/rtmutex.c | 26 +++++++++++++++++--------- kernel/locking/rwbase_rt.c | 4 +++- kernel/locking/rwsem.c | 4 ++-- kernel/locking/spinlock_rt.c | 3 ++- kernel/locking/ww_mutex.h | 29 ++++++++++++++++++----------- 6 files changed, 55 insertions(+), 28 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 2deeeca3e71b..8337ed0dbf81 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -570,6 +570,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas struct lockdep_map *nest_lock, unsigned long ip, struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) { + DEFINE_WAKE_Q(wake_q); struct mutex_waiter waiter; struct ww_mutex *ww; int ret; @@ -620,7 +621,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas */ if (__mutex_trylock(lock)) { if (ww_ctx) - __ww_mutex_check_waiters(lock, ww_ctx); + __ww_mutex_check_waiters(lock, ww_ctx, &wake_q); =20 goto skip_wait; } @@ -640,7 +641,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas * Add in stamp order, waking up waiters that must kill * themselves. */ - ret =3D __ww_mutex_add_waiter(&waiter, lock, ww_ctx); + ret =3D __ww_mutex_add_waiter(&waiter, lock, ww_ctx, &wake_q); if (ret) goto err_early_kill; } @@ -676,6 +677,11 @@ __mutex_lock_common(struct mutex *lock, unsigned int s= tate, unsigned int subclas } =20 raw_spin_unlock(&lock->wait_lock); + /* Make sure we do wakeups before calling schedule */ + if (!wake_q_empty(&wake_q)) { + wake_up_q(&wake_q); + wake_q_init(&wake_q); + } schedule_preempt_disabled(); =20 first =3D __mutex_waiter_is_first(lock, &waiter); @@ -709,7 +715,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas */ if (!ww_ctx->is_wait_die && !__mutex_waiter_is_first(lock, &waiter)) - __ww_mutex_check_waiters(lock, ww_ctx); + __ww_mutex_check_waiters(lock, ww_ctx, &wake_q); } =20 __mutex_remove_waiter(lock, &waiter); @@ -725,6 +731,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas ww_mutex_lock_acquired(ww, ww_ctx); =20 raw_spin_unlock(&lock->wait_lock); + wake_up_q(&wake_q); preempt_enable(); return 0; =20 @@ -736,6 +743,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas raw_spin_unlock(&lock->wait_lock); debug_mutex_free_waiter(&waiter); mutex_release(&lock->dep_map, ip); + wake_up_q(&wake_q); preempt_enable(); return ret; } @@ -929,6 +937,7 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne } } =20 + preempt_disable(); raw_spin_lock(&lock->wait_lock); debug_mutex_unlock(lock); if (!list_empty(&lock->wait_list)) { @@ -947,8 +956,8 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne __mutex_handoff(lock, next); =20 raw_spin_unlock(&lock->wait_lock); - wake_up_q(&wake_q); + preempt_enable(); } =20 #ifndef CONFIG_DEBUG_LOCK_ALLOC diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 4a10e8c16fd2..eaac8b196a69 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -34,13 +34,15 @@ =20 static inline int __ww_mutex_add_waiter(struct rt_mutex_waiter *waiter, struct rt_mutex *lock, - struct ww_acquire_ctx *ww_ctx) + struct ww_acquire_ctx *ww_ctx, + struct wake_q_head *wake_q) { return 0; } =20 static inline void __ww_mutex_check_waiters(struct rt_mutex *lock, - struct ww_acquire_ctx *ww_ctx) + struct ww_acquire_ctx *ww_ctx, + struct wake_q_head *wake_q) { } =20 @@ -1206,6 +1208,7 @@ static int __sched task_blocks_on_rt_mutex(struct rt_= mutex_base *lock, struct rt_mutex_waiter *top_waiter =3D waiter; struct rt_mutex_base *next_lock; int chain_walk =3D 0, res; + DEFINE_WAKE_Q(wake_q); =20 lockdep_assert_held(&lock->wait_lock); =20 @@ -1244,7 +1247,8 @@ static int __sched task_blocks_on_rt_mutex(struct rt_= mutex_base *lock, =20 /* Check whether the waiter should back out immediately */ rtm =3D container_of(lock, struct rt_mutex, rtmutex); - res =3D __ww_mutex_add_waiter(waiter, rtm, ww_ctx); + res =3D __ww_mutex_add_waiter(waiter, rtm, ww_ctx, &wake_q); + wake_up_q(&wake_q); if (res) { raw_spin_lock(&task->pi_lock); rt_mutex_dequeue(lock, waiter); @@ -1677,7 +1681,8 @@ static int __sched __rt_mutex_slowlock(struct rt_mute= x_base *lock, struct ww_acquire_ctx *ww_ctx, unsigned int state, enum rtmutex_chainwalk chwalk, - struct rt_mutex_waiter *waiter) + struct rt_mutex_waiter *waiter, + struct wake_q_head *wake_q) { struct rt_mutex *rtm =3D container_of(lock, struct rt_mutex, rtmutex); struct ww_mutex *ww =3D ww_container_of(rtm); @@ -1688,7 +1693,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mute= x_base *lock, /* Try to acquire the lock again: */ if (try_to_take_rt_mutex(lock, current, NULL)) { if (build_ww_mutex() && ww_ctx) { - __ww_mutex_check_waiters(rtm, ww_ctx); + __ww_mutex_check_waiters(rtm, ww_ctx, wake_q); ww_mutex_lock_acquired(ww, ww_ctx); } return 0; @@ -1706,7 +1711,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mute= x_base *lock, /* acquired the lock */ if (build_ww_mutex() && ww_ctx) { if (!ww_ctx->is_wait_die) - __ww_mutex_check_waiters(rtm, ww_ctx); + __ww_mutex_check_waiters(rtm, ww_ctx, wake_q); ww_mutex_lock_acquired(ww, ww_ctx); } } else { @@ -1728,7 +1733,8 @@ static int __sched __rt_mutex_slowlock(struct rt_mute= x_base *lock, =20 static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock, struct ww_acquire_ctx *ww_ctx, - unsigned int state) + unsigned int state, + struct wake_q_head *wake_q) { struct rt_mutex_waiter waiter; int ret; @@ -1737,7 +1743,7 @@ static inline int __rt_mutex_slowlock_locked(struct r= t_mutex_base *lock, waiter.ww_ctx =3D ww_ctx; =20 ret =3D __rt_mutex_slowlock(lock, ww_ctx, state, RT_MUTEX_MIN_CHAINWALK, - &waiter); + &waiter, wake_q); =20 debug_rt_mutex_free_waiter(&waiter); return ret; @@ -1753,6 +1759,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_= base *lock, struct ww_acquire_ctx *ww_ctx, unsigned int state) { + DEFINE_WAKE_Q(wake_q); unsigned long flags; int ret; =20 @@ -1774,8 +1781,9 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_= base *lock, * irqsave/restore variants. */ raw_spin_lock_irqsave(&lock->wait_lock, flags); - ret =3D __rt_mutex_slowlock_locked(lock, ww_ctx, state); + ret =3D __rt_mutex_slowlock_locked(lock, ww_ctx, state, &wake_q); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); + wake_up_q(&wake_q); rt_mutex_post_schedule(); =20 return ret; diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 34a59569db6b..e9d2f38b70f3 100644 --- a/kernel/locking/rwbase_rt.c +++ b/kernel/locking/rwbase_rt.c @@ -69,6 +69,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *r= wb, unsigned int state) { struct rt_mutex_base *rtm =3D &rwb->rtmutex; + DEFINE_WAKE_Q(wake_q); int ret; =20 rwbase_pre_schedule(); @@ -110,7 +111,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt = *rwb, * For rwlocks this returns 0 unconditionally, so the below * !ret conditionals are optimized out. */ - ret =3D rwbase_rtmutex_slowlock_locked(rtm, state); + ret =3D rwbase_rtmutex_slowlock_locked(rtm, state, &wake_q); =20 /* * On success the rtmutex is held, so there can't be a writer @@ -122,6 +123,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt = *rwb, if (!ret) atomic_inc(&rwb->readers); raw_spin_unlock_irq(&rtm->wait_lock); + wake_up_q(&wake_q); if (!ret) rwbase_rtmutex_unlock(rtm); =20 diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 2340b6d90ec6..74ebb2915d63 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1415,8 +1415,8 @@ static inline void __downgrade_write(struct rw_semaph= ore *sem) #define rwbase_rtmutex_lock_state(rtm, state) \ __rt_mutex_lock(rtm, state) =20 -#define rwbase_rtmutex_slowlock_locked(rtm, state) \ - __rt_mutex_slowlock_locked(rtm, NULL, state) +#define rwbase_rtmutex_slowlock_locked(rtm, state, wq) \ + __rt_mutex_slowlock_locked(rtm, NULL, state, wq) =20 #define rwbase_rtmutex_unlock(rtm) \ __rt_mutex_unlock(rtm) diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c index 38e292454fcc..fb1810a14c9d 100644 --- a/kernel/locking/spinlock_rt.c +++ b/kernel/locking/spinlock_rt.c @@ -162,7 +162,8 @@ rwbase_rtmutex_lock_state(struct rt_mutex_base *rtm, un= signed int state) } =20 static __always_inline int -rwbase_rtmutex_slowlock_locked(struct rt_mutex_base *rtm, unsigned int sta= te) +rwbase_rtmutex_slowlock_locked(struct rt_mutex_base *rtm, unsigned int sta= te, + struct wake_q_head *wake_q) { rtlock_slowlock_locked(rtm); return 0; diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h index 3ad2cc4823e5..7189c6631d90 100644 --- a/kernel/locking/ww_mutex.h +++ b/kernel/locking/ww_mutex.h @@ -275,7 +275,7 @@ __ww_ctx_less(struct ww_acquire_ctx *a, struct ww_acqui= re_ctx *b) */ static bool __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER *waiter, - struct ww_acquire_ctx *ww_ctx) + struct ww_acquire_ctx *ww_ctx, struct wake_q_head *wake_q) { if (!ww_ctx->is_wait_die) return false; @@ -284,7 +284,7 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER = *waiter, #ifndef WW_RT debug_mutex_wake_waiter(lock, waiter); #endif - wake_up_process(waiter->task); + wake_q_add(wake_q, waiter->task); } =20 return true; @@ -299,7 +299,8 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER = *waiter, */ static bool __ww_mutex_wound(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx, - struct ww_acquire_ctx *hold_ctx) + struct ww_acquire_ctx *hold_ctx, + struct wake_q_head *wake_q) { struct task_struct *owner =3D __ww_mutex_owner(lock); =20 @@ -331,7 +332,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock, * wakeup pending to re-read the wounded state. */ if (owner !=3D current) - wake_up_process(owner); + wake_q_add(wake_q, owner); =20 return true; } @@ -352,7 +353,8 @@ static bool __ww_mutex_wound(struct MUTEX *lock, * The current task must not be on the wait list. */ static void -__ww_mutex_check_waiters(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx) +__ww_mutex_check_waiters(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx, + struct wake_q_head *wake_q) { struct MUTEX_WAITER *cur; =20 @@ -364,8 +366,8 @@ __ww_mutex_check_waiters(struct MUTEX *lock, struct ww_= acquire_ctx *ww_ctx) if (!cur->ww_ctx) continue; =20 - if (__ww_mutex_die(lock, cur, ww_ctx) || - __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx)) + if (__ww_mutex_die(lock, cur, ww_ctx, wake_q) || + __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx, wake_q)) break; } } @@ -377,6 +379,8 @@ __ww_mutex_check_waiters(struct MUTEX *lock, struct ww_= acquire_ctx *ww_ctx) static __always_inline void ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx= *ctx) { + DEFINE_WAKE_Q(wake_q); + ww_mutex_lock_acquired(lock, ctx); =20 /* @@ -405,8 +409,10 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, s= truct ww_acquire_ctx *ctx) * die or wound us. */ lock_wait_lock(&lock->base); - __ww_mutex_check_waiters(&lock->base, ctx); + __ww_mutex_check_waiters(&lock->base, ctx, &wake_q); unlock_wait_lock(&lock->base); + + wake_up_q(&wake_q); } =20 static __always_inline int @@ -488,7 +494,8 @@ __ww_mutex_check_kill(struct MUTEX *lock, struct MUTEX_= WAITER *waiter, static inline int __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter, struct MUTEX *lock, - struct ww_acquire_ctx *ww_ctx) + struct ww_acquire_ctx *ww_ctx, + struct wake_q_head *wake_q) { struct MUTEX_WAITER *cur, *pos =3D NULL; bool is_wait_die; @@ -532,7 +539,7 @@ __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter, pos =3D cur; =20 /* Wait-Die: ensure younger waiters die. */ - __ww_mutex_die(lock, cur, ww_ctx); + __ww_mutex_die(lock, cur, ww_ctx, wake_q); } =20 __ww_waiter_add(lock, waiter, pos); @@ -550,7 +557,7 @@ __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter, * such that either we or the fastpath will wound @ww->ctx. */ smp_mb(); 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Tue, 19 Dec 2023 16:19:07 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:14 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-4-jstultz@google.com> Subject: [PATCH v7 03/23] locking/mutex: Make mutex::wait_lock irq safe From: John Stultz To: LKML Cc: Juri Lelli , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Juri Lelli mutex::wait_lock might be nested under rq->lock. Make it irq safe then. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) [rebase & fix {un,}lock_wait_lock helpers in ww_mutex.h] Signed-off-by: Connor O'Brien Signed-off-by: John Stultz --- v3: * Re-added this patch after it was dropped in v2 which caused lockdep warnings to trip. v7: * Fix function definition for PREEMPT_RT case, as pointed out by Metin Kaya. * Fix incorrect flags handling in PREEMPT_RT case as found by Metin Kaya --- kernel/locking/mutex.c | 18 ++++++++++-------- kernel/locking/ww_mutex.h | 22 +++++++++++----------- 2 files changed, 21 insertions(+), 19 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 8337ed0dbf81..73d98dd23eec 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -573,6 +573,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas DEFINE_WAKE_Q(wake_q); struct mutex_waiter waiter; struct ww_mutex *ww; + unsigned long flags; int ret; =20 if (!use_ww_ctx) @@ -615,7 +616,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas return 0; } =20 - raw_spin_lock(&lock->wait_lock); + raw_spin_lock_irqsave(&lock->wait_lock, flags); /* * After waiting to acquire the wait_lock, try again. */ @@ -676,7 +677,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas goto err; } =20 - raw_spin_unlock(&lock->wait_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); /* Make sure we do wakeups before calling schedule */ if (!wake_q_empty(&wake_q)) { wake_up_q(&wake_q); @@ -702,9 +703,9 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas trace_contention_begin(lock, LCB_F_MUTEX); } =20 - raw_spin_lock(&lock->wait_lock); + raw_spin_lock_irqsave(&lock->wait_lock, flags); } - raw_spin_lock(&lock->wait_lock); + raw_spin_lock_irqsave(&lock->wait_lock, flags); acquired: __set_current_state(TASK_RUNNING); =20 @@ -730,7 +731,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas if (ww_ctx) ww_mutex_lock_acquired(ww, ww_ctx); =20 - raw_spin_unlock(&lock->wait_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); wake_up_q(&wake_q); preempt_enable(); return 0; @@ -740,7 +741,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas __mutex_remove_waiter(lock, &waiter); err_early_kill: trace_contention_end(lock, ret); - raw_spin_unlock(&lock->wait_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); debug_mutex_free_waiter(&waiter); mutex_release(&lock->dep_map, ip); wake_up_q(&wake_q); @@ -911,6 +912,7 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne struct task_struct *next =3D NULL; DEFINE_WAKE_Q(wake_q); unsigned long owner; + unsigned long flags; =20 mutex_release(&lock->dep_map, ip); =20 @@ -938,7 +940,7 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne } =20 preempt_disable(); - raw_spin_lock(&lock->wait_lock); + raw_spin_lock_irqsave(&lock->wait_lock, flags); debug_mutex_unlock(lock); if (!list_empty(&lock->wait_list)) { /* get the first entry from the wait-list: */ @@ -955,7 +957,7 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne if (owner & MUTEX_FLAG_HANDOFF) __mutex_handoff(lock, next); =20 - raw_spin_unlock(&lock->wait_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); wake_up_q(&wake_q); preempt_enable(); } diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h index 7189c6631d90..9facc0ddfdd3 100644 --- a/kernel/locking/ww_mutex.h +++ b/kernel/locking/ww_mutex.h @@ -70,14 +70,14 @@ __ww_mutex_has_waiters(struct mutex *lock) return atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS; } =20 -static inline void lock_wait_lock(struct mutex *lock) +static inline void lock_wait_lock(struct mutex *lock, unsigned long *flags) { - raw_spin_lock(&lock->wait_lock); + raw_spin_lock_irqsave(&lock->wait_lock, *flags); } =20 -static inline void unlock_wait_lock(struct mutex *lock) +static inline void unlock_wait_lock(struct mutex *lock, unsigned long *fla= gs) { - raw_spin_unlock(&lock->wait_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, *flags); } =20 static inline void lockdep_assert_wait_lock_held(struct mutex *lock) @@ -144,14 +144,14 @@ __ww_mutex_has_waiters(struct rt_mutex *lock) return rt_mutex_has_waiters(&lock->rtmutex); } =20 -static inline void lock_wait_lock(struct rt_mutex *lock) +static inline void lock_wait_lock(struct rt_mutex *lock, unsigned long *fl= ags) { - raw_spin_lock(&lock->rtmutex.wait_lock); + raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags); } =20 -static inline void unlock_wait_lock(struct rt_mutex *lock) +static inline void unlock_wait_lock(struct rt_mutex *lock, unsigned long *= flags) { - raw_spin_unlock(&lock->rtmutex.wait_lock); + raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, *flags); } =20 static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock) @@ -380,6 +380,7 @@ static __always_inline void ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx= *ctx) { DEFINE_WAKE_Q(wake_q); + unsigned long flags; =20 ww_mutex_lock_acquired(lock, ctx); =20 @@ -408,10 +409,9 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, s= truct ww_acquire_ctx *ctx) * Uh oh, we raced in fastpath, check if any of the waiters need to * die or wound us. */ - lock_wait_lock(&lock->base); + lock_wait_lock(&lock->base, &flags); __ww_mutex_check_waiters(&lock->base, ctx, &wake_q); - unlock_wait_lock(&lock->base); - + unlock_wait_lock(&lock->base, &flags); wake_up_q(&wake_q); } =20 --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ECE6179D8 for ; Wed, 20 Dec 2023 00:19:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; 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Tue, 19 Dec 2023 16:19:09 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:15 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-5-jstultz@google.com> Subject: [PATCH v7 04/23] locking/mutex: Expose __mutex_owner() From: John Stultz To: LKML Cc: Juri Lelli , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Juri Lelli Implementing proxy execution requires that scheduler code be able to identify the current owner of a mutex. Expose __mutex_owner() for this purpose (alone!). Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Juri Lelli [Removed the EXPORT_SYMBOL] Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien [jstultz: Reworked per Peter's suggestions] Signed-off-by: John Stultz --- v4: * Move __mutex_owner() to kernel/locking/mutex.h instead of adding a new globally available accessor function to keep the exposure of this low, along with keeping it an inline function, as suggested by PeterZ --- kernel/locking/mutex.c | 25 ------------------------- kernel/locking/mutex.h | 25 +++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 25 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 73d98dd23eec..543774506fdb 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -56,31 +56,6 @@ __mutex_init(struct mutex *lock, const char *name, struc= t lock_class_key *key) } EXPORT_SYMBOL(__mutex_init); =20 -/* - * @owner: contains: 'struct task_struct *' to the current lock owner, - * NULL means not owned. Since task_struct pointers are aligned at - * at least L1_CACHE_BYTES, we have low bits to store extra state. - * - * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. - * Bit1 indicates unlock needs to hand the lock to the top-waiter - * Bit2 indicates handoff has been done and we're waiting for pickup. - */ -#define MUTEX_FLAG_WAITERS 0x01 -#define MUTEX_FLAG_HANDOFF 0x02 -#define MUTEX_FLAG_PICKUP 0x04 - -#define MUTEX_FLAGS 0x07 - -/* - * Internal helper function; C doesn't allow us to hide it :/ - * - * DO NOT USE (outside of mutex code). - */ -static inline struct task_struct *__mutex_owner(struct mutex *lock) -{ - return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLA= GS); -} - static inline struct task_struct *__owner_task(unsigned long owner) { return (struct task_struct *)(owner & ~MUTEX_FLAGS); diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h index 0b2a79c4013b..1c7d3d32def8 100644 --- a/kernel/locking/mutex.h +++ b/kernel/locking/mutex.h @@ -20,6 +20,31 @@ struct mutex_waiter { #endif }; =20 +/* + * @owner: contains: 'struct task_struct *' to the current lock owner, + * NULL means not owned. Since task_struct pointers are aligned at + * at least L1_CACHE_BYTES, we have low bits to store extra state. + * + * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. + * Bit1 indicates unlock needs to hand the lock to the top-waiter + * Bit2 indicates handoff has been done and we're waiting for pickup. + */ +#define MUTEX_FLAG_WAITERS 0x01 +#define MUTEX_FLAG_HANDOFF 0x02 +#define MUTEX_FLAG_PICKUP 0x04 + +#define MUTEX_FLAGS 0x07 + +/* + * Internal helper function; C doesn't allow us to hide it :/ + * + * DO NOT USE (outside of mutex & scheduler code). + */ +static inline struct task_struct *__mutex_owner(struct mutex *lock) +{ + return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLA= GS); +} + #ifdef CONFIG_DEBUG_MUTEXES extern void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter); --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F1D2CAD2E for ; Wed, 20 Dec 2023 00:19:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="N1oZrSP2" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-5ca5b61c841so2045759a12.3 for ; Tue, 19 Dec 2023 16:19:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031552; x=1703636352; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=sqfwQXYrs0dla1Ln+uFCJhXbwMO3b1s4DQoQ/IjlTnQ=; b=N1oZrSP2R+R2WerPrKUNgaQ9//qFIntPz3SemUYd3IsVr7A+oTP/IdePvYsYdyyXZQ AX+MoE9gniRQtLGneHUfadpYqcbJGytt3OsIu6lu3SDAvhR4I32w7RYfRDvmY8pFpNkW cIVyFy3CTXFp+b2QmX8VDdPqeHtvNVInGPCe17k3gEF+8FnkjqNfv3gQruE7oNb5+Sh/ jGRoBEEHZvMWzT6CwwZBQr1ePKowQatHu9pg+mygLBV2hCz3R3wKAlsye3evAzElyIfP H90ojml5Xh1Z9Z/2fQ2xK8iXGqVz47UksLxD6tiLe+wWu9tCv0KNLyMc+272geAE8POD CPfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031552; x=1703636352; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=sqfwQXYrs0dla1Ln+uFCJhXbwMO3b1s4DQoQ/IjlTnQ=; b=SA13avKNdzLQy/ya57opfWxnMSaKB5AKzTzfLqkij24vGhLaLv4XXF2nXvbIZCQYMf cTr/AM8KlbtN4+zQUfeb/j2Lpyb2ecrdXI1fr1heIb1NgRNN8/1weGajCWzaV7xRnCpj dpDVNS6xBJ0pfGsLyfqlX4IzHSUk6B5O6ICvNZ0fmLu1zvT4GrEMPNFhtBzBW7u/8dqT E3qhxJAaoE63s1MMZBioa5Tqie6la4PFhp6CiTYkMcs7FuedHtdgwRHAZOsbxIhAU7M0 JbOzfiSs0NVgDZLY++u4wCGbIXpHCFZnxhThmlDb9fUFDT45+nKEDjbcpuggmsOnwsOL G4hQ== X-Gm-Message-State: AOJu0Ywzw1L7fBB2kWzlHePyrjfFqmG1n/ZXsrH87EN4yn9qYmHuAZBy c069+r5G9HxyUt30/ge7P4uXG7pjiY5ZhrGVFpVuT1DgjkIcv39BuhHUgDkWU+z8SpNtJ4fHDSU GrR69TRlF4JfymYge81TvfanWx2pzVVNZwfGMGDHB9y0CITYERcI6Yyofa6qaJPOm5MDwmg0= X-Google-Smtp-Source: AGHT+IGh6Z6BHPJUwvSt9BuByFFALZMShZzYYkaVsrXYhrA6wg1FQNteSkJIydioVggPy4D54upfw0/x8kyV X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6a02:68a:b0:5cd:a34c:f9db with SMTP id ca10-20020a056a02068a00b005cda34cf9dbmr23155pgb.10.1703031551064; Tue, 19 Dec 2023 16:19:11 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:16 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-6-jstultz@google.com> Subject: [PATCH v7 05/23] locking/mutex: Rework task_struct::blocked_on From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Track the blocked-on relation for mutexes, to allow following this relation at schedule time. task | blocked-on v mutex | owner v task Also adds a blocked_on_state value so we can distinguqish when a task is blocked_on a mutex, but is either blocked, waking up, or runnable (such that it can try to aquire the lock its blocked on). This avoids some of the subtle & racy games where the blocked_on state gets cleared, only to have it re-added by the mutex_lock_slowpath call when it tries to aquire the lock on wakeup Also adds blocked_lock to the task_struct so we can safely serialize the blocked-on state. Finally adds wrappers that are useful to provide correctness checks. Folded in from a patch by: Valentin Schneider This all will be used for tracking blocked-task/mutex chains with the prox-execution patch in a similar fashion to how priority inheritence is done with rt_mutexes. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) [minor changes while rebasing] Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Connor O'Brien [jstultz: Fix blocked_on tracking in __mutex_lock_common in error paths] Signed-off-by: John Stultz --- v2: * Fixed blocked_on tracking in error paths that was causing crashes v4: * Ensure we clear blocked_on when waking ww_mutexes to die or wound. This is critical so we don't get ciruclar blocked_on relationships that can't be resolved. v5: * Fix potential bug where the skip_wait path might clear blocked_on when that path never set it * Slight tweaks to where we set blocked_on to make it consistent, along with extra WARN_ON correctness checking * Minor comment changes v7: * Minor commit message change suggested by Metin Kaya * Fix WARN_ON conditionals in unlock path (as blocked_on might already be cleared), found while looking at issue Metin Kaya raised. * Minor tweaks to be consistent in what we do under the blocked_on lock, also tweaked variable name to avoid confusion with label, and comment typos, as suggested by Metin Kaya * Minor tweak for CONFIG_SCHED_PROXY_EXEC name change * Moved unused block of code to later in the series, as suggested by Metin Kaya * Switch to a tri-state to be able to distinguish from waking and runnable so we can later safely do return migration from ttwu * Folded together with related blocked_on changes --- include/linux/sched.h | 40 ++++++++++++++++++++++++++++++++---- init/init_task.c | 1 + kernel/fork.c | 4 ++-- kernel/locking/mutex-debug.c | 9 ++++---- kernel/locking/mutex.c | 35 +++++++++++++++++++++++++++---- kernel/locking/ww_mutex.h | 24 ++++++++++++++++++++-- kernel/sched/core.c | 6 ++++++ 7 files changed, 103 insertions(+), 16 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 1e80c330f755..bfe8670f99a1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -743,6 +743,12 @@ struct kmap_ctrl { #endif }; =20 +enum blocked_on_state { + BO_RUNNABLE, + BO_BLOCKED, + BO_WAKING, +}; + struct task_struct { #ifdef CONFIG_THREAD_INFO_IN_TASK /* @@ -1149,10 +1155,9 @@ struct task_struct { struct rt_mutex_waiter *pi_blocked_on; #endif =20 -#ifdef CONFIG_DEBUG_MUTEXES - /* Mutex deadlock detection: */ - struct mutex_waiter *blocked_on; -#endif + enum blocked_on_state blocked_on_state; + struct mutex *blocked_on; /* lock we're blocked on */ + raw_spinlock_t blocked_lock; =20 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP int non_block_count; @@ -2258,6 +2263,33 @@ static inline int rwlock_needbreak(rwlock_t *lock) #endif } =20 +static inline void set_task_blocked_on(struct task_struct *p, struct mutex= *m) +{ + lockdep_assert_held(&p->blocked_lock); + + /* + * Check we are clearing values to NULL or setting NULL + * to values to ensure we don't overwrite exisiting mutex + * values or clear already cleared values + */ + WARN_ON((!m && !p->blocked_on) || (m && p->blocked_on)); + + p->blocked_on =3D m; + p->blocked_on_state =3D m ? BO_BLOCKED : BO_RUNNABLE; +} + +static inline struct mutex *get_task_blocked_on(struct task_struct *p) +{ + lockdep_assert_held(&p->blocked_lock); + + return p->blocked_on; +} + +static inline struct mutex *get_task_blocked_on_once(struct task_struct *p) +{ + return READ_ONCE(p->blocked_on); +} + static __always_inline bool need_resched(void) { return unlikely(tif_need_resched()); diff --git a/init/init_task.c b/init/init_task.c index 5727d42149c3..0c31d7d7c7a9 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -131,6 +131,7 @@ struct task_struct init_task .journal_info =3D NULL, INIT_CPU_TIMERS(init_task) .pi_lock =3D __RAW_SPIN_LOCK_UNLOCKED(init_task.pi_lock), + .blocked_lock =3D __RAW_SPIN_LOCK_UNLOCKED(init_task.blocked_lock), .timer_slack_ns =3D 50000, /* 50 usec default slack */ .thread_pid =3D &init_struct_pid, .thread_node =3D LIST_HEAD_INIT(init_signals.thread_head), diff --git a/kernel/fork.c b/kernel/fork.c index 10917c3e1f03..b3ba3d22d8b2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2358,6 +2358,7 @@ __latent_entropy struct task_struct *copy_process( ftrace_graph_init_task(p); =20 rt_mutex_init_task(p); + raw_spin_lock_init(&p->blocked_lock); =20 lockdep_assert_irqs_enabled(); #ifdef CONFIG_PROVE_LOCKING @@ -2456,9 +2457,8 @@ __latent_entropy struct task_struct *copy_process( lockdep_init_task(p); #endif =20 -#ifdef CONFIG_DEBUG_MUTEXES + p->blocked_on_state =3D BO_RUNNABLE; p->blocked_on =3D NULL; /* not blocked yet */ -#endif #ifdef CONFIG_BCACHE p->sequential_io =3D 0; p->sequential_io_avg =3D 0; diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c index bc8abb8549d2..1eedf7c60c00 100644 --- a/kernel/locking/mutex-debug.c +++ b/kernel/locking/mutex-debug.c @@ -52,17 +52,18 @@ void debug_mutex_add_waiter(struct mutex *lock, struct = mutex_waiter *waiter, { lockdep_assert_held(&lock->wait_lock); =20 - /* Mark the current thread as blocked on the lock: */ - task->blocked_on =3D waiter; + /* Current thread can't be already blocked (since it's executing!) */ + DEBUG_LOCKS_WARN_ON(get_task_blocked_on(task)); } =20 void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *wa= iter, struct task_struct *task) { + struct mutex *blocked_on =3D get_task_blocked_on_once(task); + DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list)); DEBUG_LOCKS_WARN_ON(waiter->task !=3D task); - DEBUG_LOCKS_WARN_ON(task->blocked_on !=3D waiter); - task->blocked_on =3D NULL; + DEBUG_LOCKS_WARN_ON(blocked_on && blocked_on !=3D lock); =20 INIT_LIST_HEAD(&waiter->list); waiter->task =3D NULL; diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 543774506fdb..6084470773f6 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -592,6 +592,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas } =20 raw_spin_lock_irqsave(&lock->wait_lock, flags); + raw_spin_lock(¤t->blocked_lock); /* * After waiting to acquire the wait_lock, try again. */ @@ -622,6 +623,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas goto err_early_kill; } =20 + set_task_blocked_on(current, lock); set_current_state(state); trace_contention_begin(lock, LCB_F_MUTEX); for (;;) { @@ -652,6 +654,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int st= ate, unsigned int subclas goto err; } =20 + raw_spin_unlock(¤t->blocked_lock); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); /* Make sure we do wakeups before calling schedule */ if (!wake_q_empty(&wake_q)) { @@ -662,6 +665,13 @@ __mutex_lock_common(struct mutex *lock, unsigned int s= tate, unsigned int subclas =20 first =3D __mutex_waiter_is_first(lock, &waiter); =20 + raw_spin_lock_irqsave(&lock->wait_lock, flags); + raw_spin_lock(¤t->blocked_lock); + + /* + * Re-set blocked_on_state as unlock path set it to WAKING/RUNNABLE + */ + current->blocked_on_state =3D BO_BLOCKED; set_current_state(state); /* * Here we order against unlock; we must either see it change @@ -672,16 +682,25 @@ __mutex_lock_common(struct mutex *lock, unsigned int = state, unsigned int subclas break; =20 if (first) { + bool opt_acquired; + + /* + * mutex_optimistic_spin() can schedule, so we need to + * release these locks before calling it. + */ + raw_spin_unlock(¤t->blocked_lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN); - if (mutex_optimistic_spin(lock, ww_ctx, &waiter)) + opt_acquired =3D mutex_optimistic_spin(lock, ww_ctx, &waiter); + raw_spin_lock_irqsave(&lock->wait_lock, flags); + raw_spin_lock(¤t->blocked_lock); + if (opt_acquired) break; trace_contention_begin(lock, LCB_F_MUTEX); } - - raw_spin_lock_irqsave(&lock->wait_lock, flags); } - raw_spin_lock_irqsave(&lock->wait_lock, flags); acquired: + set_task_blocked_on(current, NULL); __set_current_state(TASK_RUNNING); =20 if (ww_ctx) { @@ -706,16 +725,20 @@ __mutex_lock_common(struct mutex *lock, unsigned int = state, unsigned int subclas if (ww_ctx) ww_mutex_lock_acquired(ww, ww_ctx); =20 + raw_spin_unlock(¤t->blocked_lock); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); wake_up_q(&wake_q); preempt_enable(); return 0; =20 err: + set_task_blocked_on(current, NULL); __set_current_state(TASK_RUNNING); __mutex_remove_waiter(lock, &waiter); err_early_kill: + WARN_ON(current->blocked_on); trace_contention_end(lock, ret); + raw_spin_unlock(¤t->blocked_lock); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); debug_mutex_free_waiter(&waiter); mutex_release(&lock->dep_map, ip); @@ -925,8 +948,12 @@ static noinline void __sched __mutex_unlock_slowpath(s= truct mutex *lock, unsigne =20 next =3D waiter->task; =20 + raw_spin_lock(&next->blocked_lock); debug_mutex_wake_waiter(lock, waiter); + WARN_ON(next->blocked_on !=3D lock); + next->blocked_on_state =3D BO_WAKING; wake_q_add(&wake_q, next); + raw_spin_unlock(&next->blocked_lock); } =20 if (owner & MUTEX_FLAG_HANDOFF) diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h index 9facc0ddfdd3..8dd21ff5eee0 100644 --- a/kernel/locking/ww_mutex.h +++ b/kernel/locking/ww_mutex.h @@ -281,10 +281,21 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITE= R *waiter, return false; =20 if (waiter->ww_ctx->acquired > 0 && __ww_ctx_less(waiter->ww_ctx, ww_ctx)= ) { + /* nested as we should hold current->blocked_lock already */ + raw_spin_lock_nested(&waiter->task->blocked_lock, SINGLE_DEPTH_NESTING); #ifndef WW_RT debug_mutex_wake_waiter(lock, waiter); #endif + /* + * When waking up the task to die, be sure to set the + * blocked_on_state to WAKING. Otherwise we can see + * circular blocked_on relationships that can't + * resolve. + */ + WARN_ON(waiter->task->blocked_on !=3D lock); + waiter->task->blocked_on_state =3D BO_WAKING; wake_q_add(wake_q, waiter->task); + raw_spin_unlock(&waiter->task->blocked_lock); } =20 return true; @@ -331,9 +342,18 @@ static bool __ww_mutex_wound(struct MUTEX *lock, * it's wounded in __ww_mutex_check_kill() or has a * wakeup pending to re-read the wounded state. */ - if (owner !=3D current) + if (owner !=3D current) { + /* nested as we should hold current->blocked_lock already */ + raw_spin_lock_nested(&owner->blocked_lock, SINGLE_DEPTH_NESTING); + /* + * When waking up the task to wound, be sure to set the + * blocked_on_state flag. Otherwise we can see circular + * blocked_on relationships that can't resolve. + */ + owner->blocked_on_state =3D BO_WAKING; wake_q_add(wake_q, owner); - + raw_spin_unlock(&owner->blocked_lock); + } return true; } =20 diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a708d225c28e..4e46189d545d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4195,6 +4195,7 @@ bool ttwu_state_match(struct task_struct *p, unsigned= int state, int *success) int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_fla= gs) { guard(preempt)(); + unsigned long flags; int cpu, success =3D 0; =20 if (p =3D=3D current) { @@ -4341,6 +4342,11 @@ int try_to_wake_up(struct task_struct *p, unsigned i= nt state, int wake_flags) =20 ttwu_queue(p, cpu, wake_flags); } + /* XXX can we do something better here for !CONFIG_SCHED_PROXY_EXEC case = */ + raw_spin_lock_irqsave(&p->blocked_lock, flags); + if (p->blocked_on_state =3D=3D BO_WAKING) + p->blocked_on_state =3D BO_RUNNABLE; + raw_spin_unlock_irqrestore(&p->blocked_lock, flags); out: if (success) ttwu_stat(p, task_cpu(p), wake_flags); --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4DEDAB64F for ; Wed, 20 Dec 2023 00:19:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ePJbYj50" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5cf4696e202so67923457b3.2 for ; Tue, 19 Dec 2023 16:19:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031553; x=1703636353; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=R4gN3By35m9Oev8xh3bj9l9i7deQm7lEgF77PrA60M4=; b=ePJbYj50mEx75GgLkfCRl2N1CTA2OgV374FJNQvOQExrauWzIrHkcMfcDXowGqMEWq GisyGDyWaYoLATTmbpDkz+ui3ILBqOICVjAGtUuAl7w+cmBuMGHlAbiMBfKbomd/33KZ 1E+gd+5nHbDWvU7o/welF2+SoCIZ0tkyUMWz1AUP7INTEKKAc62k+HeHmWi3rDl8wSpd aw6ea3NWHpzGudaRSPMMLPUPT3EBcoMslErK80l+N9BA8zXhYBOKRNGjAWApjUIUkvXj kTKJ3T6yup6bU8zck8fKeGKbik5F032EBH+Xuvp/Ghh0bf4YVRVMLuCINt3q1I3cMjNS o2jA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031553; x=1703636353; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=R4gN3By35m9Oev8xh3bj9l9i7deQm7lEgF77PrA60M4=; b=jm4cXp0z3tg7AZra85VLn872IszJk0pmWIyWomoL68FFy8ZU3OjqumbyikE+lvutT+ /DcSzPmTk1ppDq49Adoc9rQF/q55QTuaV7jcdPhRrOQmZuW0OC6x0WPW2qKnl3at7Cs7 FE2VooX3BFTx8qm22a1NJM/YmmQxw8/7NRR9jUY7BpPbRgjCmQC1nyj0bTFg03RNGiCH QpYj5F3T8lyLCUO2d9maCGEpJ+h8+OK2eu2b2w9S11QZJBZjMrZ6RdQo98VWJPjRS+qs 0pyuWMkCd3Kz6tVGlpqDMorNZW/Yb6ZMLEE6SlOnXBUqhFNsThkjp7vq51j74JgFpADT /5yg== X-Gm-Message-State: AOJu0Yy7PUHSv1wBUzjF929JACtVQrDE1f55iVONg9qmXCeYIwqRWmBL 2xGNizYG6XKB6c6ZdjCYEymMZA9MbTEG4h/o9CHAKgUEVnn8T3jP5KJ1h2oTLZoroVU8+WfM4MI SW3HguTgFDG48erR5SwLXkZUukcLRUOqJOmCxhOlb4muOEqgUXcmEQqi5kcw9WNSt8II/3so= X-Google-Smtp-Source: AGHT+IFTRDyLyo4xM/u+37VsmESEsy4LtuVDSD58dzoRhs6ZUZnQrBulUNuz8RlZBhWXmmvvP5Ns81A3uWhG X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a81:fe0b:0:b0:5e6:468e:fea0 with SMTP id j11-20020a81fe0b000000b005e6468efea0mr2377004ywn.0.1703031553048; Tue, 19 Dec 2023 16:19:13 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:17 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-7-jstultz@google.com> Subject: [PATCH v7 06/23] sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument sched_prox_exec=3D that can be used to disable the feature at boot time if CONFIG_SCHED_PROXY_EXEC was enabled. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- v7: * Switch to CONFIG_SCHED_PROXY_EXEC/sched_proxy_exec=3D as suggested by Metin Kaya. * Switch boot arg from =3Ddisable/enable to use kstrtobool(), which supports =3Dyes|no|1|0|true|false|on|off, as also suggested by Metin Kaya, and print a message when a boot argument is used. --- .../admin-guide/kernel-parameters.txt | 5 ++++ include/linux/sched.h | 13 +++++++++ init/Kconfig | 7 +++++ kernel/sched/core.c | 29 +++++++++++++++++++ 4 files changed, 54 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 65731b060e3f..cc64393b913f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5714,6 +5714,11 @@ sa1100ir [NET] See drivers/net/irda/sa1100_ir.c. =20 + sched_proxy_exec=3D [KNL] + Enables or disables "proxy execution" style + solution to mutex based priority inversion. + Format: + sched_verbose [KNL] Enables verbose scheduler debug messages. =20 schedstats=3D [KNL,X86] Enable or disable scheduled statistics. diff --git a/include/linux/sched.h b/include/linux/sched.h index bfe8670f99a1..880af1c3097d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1566,6 +1566,19 @@ struct task_struct { */ }; =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +DECLARE_STATIC_KEY_TRUE(__sched_proxy_exec); +static inline bool sched_proxy_exec(void) +{ + return static_branch_likely(&__sched_proxy_exec); +} +#else +static inline bool sched_proxy_exec(void) +{ + return false; +} +#endif + static inline struct pid *task_pid(struct task_struct *task) { return task->thread_pid; diff --git a/init/Kconfig b/init/Kconfig index 9ffb103fc927..c5a759b6366a 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -908,6 +908,13 @@ config NUMA_BALANCING_DEFAULT_ENABLED If set, automatic NUMA balancing will be enabled if running on a NUMA machine. =20 +config SCHED_PROXY_EXEC + bool "Proxy Execution" + default n + help + This option enables proxy execution, a mechanism for mutex owning + tasks to inherit the scheduling context of higher priority waiters. + menuconfig CGROUPS bool "Control Group support" select KERNFS diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4e46189d545d..e06558fb08aa 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -117,6 +117,35 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); =20 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec); +static int __init setup_proxy_exec(char *str) +{ + bool proxy_enable; + + if (kstrtobool(str, &proxy_enable)) { + pr_warn("Unable to parse sched_proxy_exec=3D\n"); + return 0; + } + + if (proxy_enable) { + pr_info("sched_proxy_exec enabled via boot arg\n"); + static_branch_enable(&__sched_proxy_exec); + } else { + pr_info("sched_proxy_exec disabled via boot arg\n"); + static_branch_disable(&__sched_proxy_exec); + } + return 1; +} +#else +static int __init setup_proxy_exec(char *str) +{ + pr_warn("CONFIG_SCHED_PROXY_EXEC=3Dn, so it cannot be enabled or disabled= at boottime\n"); + return 0; +} +#endif +__setup("sched_proxy_exec=3D", setup_proxy_exec); + #ifdef CONFIG_SCHED_DEBUG /* * Debugging: various feature bits --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29E2DBE5E for ; 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Tue, 19 Dec 2023 16:19:14 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:18 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-8-jstultz@google.com> Subject: [PATCH v7 07/23] locking/mutex: Switch to mutex handoffs for CONFIG_SCHED_PROXY_EXEC From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Since with SCHED_PROXY_EXEC, we will want to hand off locks to the tasks we are running on behalf of, switch to using mutex handoffs. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) [rebased, added comments and changelog] Signed-off-by: Juri Lelli [Fixed rebase conflicts] [squashed sched: Ensure blocked_on is always guarded by blocked_lock] Signed-off-by: Valentin Schneider [fix rebase conflicts, various fixes & tweaks commented inline] [squashed sched: Use rq->curr vs rq->proxy checks] Signed-off-by: Connor O'Brien [jstultz: Split out only the very basic initial framework for proxy logic from a larger patch.] Signed-off-by: John Stultz --- v5: * Split out from core proxy patch v6: * Rework to use sched_proxy_exec() instead of #ifdef CONFIG_PROXY_EXEC v7: * Avoid disabling optimistic spinning at compile time so booting with sched_proxy_exec=3Doff matches prior performance * Add comment in mutex-design.rst as suggested by Metin Kaya --- Documentation/locking/mutex-design.rst | 3 ++ kernel/locking/mutex.c | 42 +++++++++++++++----------- 2 files changed, 28 insertions(+), 17 deletions(-) diff --git a/Documentation/locking/mutex-design.rst b/Documentation/locking= /mutex-design.rst index 78540cd7f54b..57a5cb03f409 100644 --- a/Documentation/locking/mutex-design.rst +++ b/Documentation/locking/mutex-design.rst @@ -61,6 +61,9 @@ taken, depending on the state of the lock: waiting to spin on mutex owner, only to go directly to slowpath upon obtaining the MCS lock. =20 + NOTE: Optimistic spinning will be avoided when using proxy execution + (SCHED_PROXY_EXEC) as we want to hand the lock off to the task that w= as + boosting the current owner. =20 (iii) slowpath: last resort, if the lock is still unable to be acquired, the task is added to the wait-queue and sleeps until woken up by the diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 6084470773f6..11dc5cb7a5a3 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -416,6 +416,9 @@ static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) { + if (sched_proxy_exec()) + return false; + if (!waiter) { /* * The purpose of the mutex_can_spin_on_owner() function is @@ -914,26 +917,31 @@ static noinline void __sched __mutex_unlock_slowpath(= struct mutex *lock, unsigne =20 mutex_release(&lock->dep_map, ip); =20 - /* - * Release the lock before (potentially) taking the spinlock such that - * other contenders can get on with things ASAP. - * - * Except when HANDOFF, in that case we must not clear the owner field, - * but instead set it to the top waiter. - */ - owner =3D atomic_long_read(&lock->owner); - for (;;) { - MUTEX_WARN_ON(__owner_task(owner) !=3D current); - MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP); - - if (owner & MUTEX_FLAG_HANDOFF) - break; + if (sched_proxy_exec()) { + /* Always force HANDOFF for Proxy Exec for now. Revisit. */ + owner =3D MUTEX_FLAG_HANDOFF; + } else { + /* + * Release the lock before (potentially) taking the spinlock + * such that other contenders can get on with things ASAP. + * + * Except when HANDOFF, in that case we must not clear the + * owner field, but instead set it to the top waiter. + */ + owner =3D atomic_long_read(&lock->owner); + for (;;) { + MUTEX_WARN_ON(__owner_task(owner) !=3D current); + MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP); =20 - if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(= owner))) { - if (owner & MUTEX_FLAG_WAITERS) + if (owner & MUTEX_FLAG_HANDOFF) break; =20 - return; + if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, + __owner_flags(owner))) { + if (owner & MUTEX_FLAG_WAITERS) + break; + return; + } } } =20 --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 30632748C for ; Wed, 20 Dec 2023 00:19:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bwz6nykz" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dbd4a080c0bso2649248276.1 for ; Tue, 19 Dec 2023 16:19:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031557; x=1703636357; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=oaiagOlY2yIt6EK/2XFKSdkelCGW18s3codp/jhpWBM=; b=bwz6nykzmkIWGdCr1EJDLaVn1u4PbOs3bpvbU45haNGX8frTRMhcPUsi68bpRF3eg3 erMSgp+YL2qGBXRR1EFCIPYmwzgrOUGAakqHtEa23zea1OP+BWwWLrVURLSGEHgBpILq zRutLEVscxD8jpAweHiRg7/P9n2wQHo3xtBq/bivIKWdqPD/zbxyzpwBpFC4mF88My4w RCMD9B35Q1ZUtPO/epa6sXP+TfLGF3KaXYwQxo4Leo6OMGtRwCIXTVnLKBzaN7FSVOEt O7H0xIYLUKkoiA2Qlxzp293xhF+kwNP2UfTxfP+1ADdhNSZE+q+dC9OMgKkXdeLgXKEJ Loqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031557; x=1703636357; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=oaiagOlY2yIt6EK/2XFKSdkelCGW18s3codp/jhpWBM=; b=OSP+eEPJFgBCZ3IjSa193aiarA21FL95IcWn1JyhZvdq/IKKOzqzy4oQ120OsF1Q7v RdajXtPq4XX9nKnNcPzbooUR+lT1I1LMa55474empb8OYzw7Vm5sFzmwrbydj6KnYMpY XHfOh3aG4DNPQbQJ7kl1AGhk17c7XiHEXPrewPPTOLIcEmLffpRnMiGEbRlc7Tg13dAo 40UEgnOWg83gl+CDavU5HlqtLYYYhP9GE0WFT/kYMNyryv9gVVcbSmcieFI4CCLgfE+z TcHsZxVH8fC5R4BEC1WX1oPxPFXVaZ+/uceaP+xOo5H89r3rgmgGnWP6nQgVcOQr7JXc ZKxA== X-Gm-Message-State: AOJu0YzJgEVA1v3dVxwvXiMWSXY5y9BbTehLeNTsxe2JK1Jdk4Efj+Uo crlB/xqrqpC/q6W0DwFFVujRR3gICVN006RMWLHBdCPFAE15usdOtUDnnqtVhhmmkFEsQIEHkSB UanmdfgbQOjakz/KB4JyqaGoj5tMQTk7yK1wgVk/M5jwEzfedqiEJhaLjRf0/zhYOnbh9lnc= X-Google-Smtp-Source: AGHT+IEk5kzkoyXxgClT4wlkTjRmZvesGSdT9maK6Vao9SNI3mL1m0p2Iu8eWuJOPmuBRh3ybmn7JX1oh0OW X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6902:1341:b0:dbd:ab89:659d with SMTP id g1-20020a056902134100b00dbdab89659dmr22428ybu.3.1703031556773; Tue, 19 Dec 2023 16:19:16 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:19 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-9-jstultz@google.com> Subject: [PATCH v7 08/23] sched: Split scheduler and execution contexts From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Xuewen Yan , K Prateek Nayak , Metin Kaya , Thomas Gleixner , kernel-team@android.com, "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Let's define the scheduling context as all the scheduler state in task_struct for the task selected to run, and the execution context as all state required to actually run the task. Currently both are intertwined in task_struct. We want to logically split these such that we can use the scheduling context of the task selected to be scheduled, but use the execution context of a different task to actually be run. To this purpose, introduce rq_selected() macro to point to the task_struct selected from the runqueue by the scheduler, and will be used for scheduler state, and preserve rq->curr to indicate the execution context of the task that will actually be run. NOTE: Peter previously mentioned he didn't like the name "rq_selected()", but I've not come up with a better alternative. I'm very open to other name proposals. Question for Peter: Dietmar suggested you'd prefer I drop the conditionalization of the scheduler context pointer on the rq (so rq_selected() would be open coded as rq->curr_selected or whatever we agree on for a name), but I'd think in the !CONFIG_PROXY_EXEC case we'd want to avoid the wasted pointer and its use (since it curr_selected would always be =3D=3D curr)? If I'm wrong I'm fine switching this, but would appreciate clarification. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Metin Kaya Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20181009092434.26221-5-juri.lelli@redhat.com [add additional comments and update more sched_class code to use rq::proxy] Signed-off-by: Connor O'Brien [jstultz: Rebased and resolved minor collisions, reworked to use accessors, tweaked update_curr_common to use rq_proxy fixing rt scheduling issues] Signed-off-by: John Stultz --- v2: * Reworked to use accessors * Fixed update_curr_common to use proxy instead of curr v3: * Tweaked wrapper names * Swapped proxy for selected for clarity v4: * Minor variable name tweaks for readability * Use a macro instead of a inline function and drop other helper functions as suggested by Peter. * Remove verbose comments/questions to avoid review distractions, as suggested by Dietmar v5: * Add CONFIG_PROXY_EXEC option to this patch so the new logic can be tested with this change * Minor fix to grab rq_selected when holding the rq lock v7: * Minor spelling fix and unused argument fixes suggested by Metin Kaya * Switch to curr_selected for consistency, and minor rewording of commit message for clarity * Rename variables selected instead of curr when we're using rq_selected() * Reduce macros in CONFIG_SCHED_PROXY_EXEC ifdef sections, as suggested by Metin Kaya --- kernel/sched/core.c | 46 ++++++++++++++++++++++++++--------------- kernel/sched/deadline.c | 35 ++++++++++++++++--------------- kernel/sched/fair.c | 18 ++++++++-------- kernel/sched/rt.c | 40 +++++++++++++++++------------------ kernel/sched/sched.h | 35 +++++++++++++++++++++++++++++-- 5 files changed, 109 insertions(+), 65 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e06558fb08aa..0ce34f5c0e0c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -822,7 +822,7 @@ static enum hrtimer_restart hrtick(struct hrtimer *time= r) =20 rq_lock(rq, &rf); update_rq_clock(rq); - rq->curr->sched_class->task_tick(rq, rq->curr, 1); + rq_selected(rq)->sched_class->task_tick(rq, rq_selected(rq), 1); rq_unlock(rq, &rf); =20 return HRTIMER_NORESTART; @@ -2242,16 +2242,18 @@ static inline void check_class_changed(struct rq *r= q, struct task_struct *p, =20 void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags) { - if (p->sched_class =3D=3D rq->curr->sched_class) - rq->curr->sched_class->wakeup_preempt(rq, p, flags); - else if (sched_class_above(p->sched_class, rq->curr->sched_class)) + struct task_struct *selected =3D rq_selected(rq); + + if (p->sched_class =3D=3D selected->sched_class) + selected->sched_class->wakeup_preempt(rq, p, flags); + else if (sched_class_above(p->sched_class, selected->sched_class)) resched_curr(rq); =20 /* * A queue event has occurred, and we're going to schedule. In * this case, we can save a useless back to back clock update. */ - if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) + if (task_on_rq_queued(selected) && test_tsk_need_resched(rq->curr)) rq_clock_skip_update(rq); } =20 @@ -2780,7 +2782,7 @@ __do_set_cpus_allowed(struct task_struct *p, struct a= ffinity_context *ctx) lockdep_assert_held(&p->pi_lock); =20 queued =3D task_on_rq_queued(p); - running =3D task_current(rq, p); + running =3D task_current_selected(rq, p); =20 if (queued) { /* @@ -5600,7 +5602,7 @@ unsigned long long task_sched_runtime(struct task_str= uct *p) * project cycles that may never be accounted to this * thread, breaking clock_gettime(). */ - if (task_current(rq, p) && task_on_rq_queued(p)) { + if (task_current_selected(rq, p) && task_on_rq_queued(p)) { prefetch_curr_exec_start(p); update_rq_clock(rq); p->sched_class->update_curr(rq); @@ -5668,7 +5670,8 @@ void scheduler_tick(void) { int cpu =3D smp_processor_id(); struct rq *rq =3D cpu_rq(cpu); - struct task_struct *curr =3D rq->curr; + /* accounting goes to the selected task */ + struct task_struct *selected; struct rq_flags rf; unsigned long thermal_pressure; u64 resched_latency; @@ -5679,16 +5682,17 @@ void scheduler_tick(void) sched_clock_tick(); =20 rq_lock(rq, &rf); + selected =3D rq_selected(rq); =20 update_rq_clock(rq); thermal_pressure =3D arch_scale_thermal_pressure(cpu_of(rq)); update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure); - curr->sched_class->task_tick(rq, curr, 0); + selected->sched_class->task_tick(rq, selected, 0); if (sched_feat(LATENCY_WARN)) resched_latency =3D cpu_resched_latency(rq); calc_global_load_tick(rq); sched_core_tick(rq); - task_tick_mm_cid(rq, curr); + task_tick_mm_cid(rq, selected); =20 rq_unlock(rq, &rf); =20 @@ -5697,8 +5701,8 @@ void scheduler_tick(void) =20 perf_event_task_tick(); =20 - if (curr->flags & PF_WQ_WORKER) - wq_worker_tick(curr); + if (selected->flags & PF_WQ_WORKER) + wq_worker_tick(selected); =20 #ifdef CONFIG_SMP rq->idle_balance =3D idle_cpu(cpu); @@ -5763,6 +5767,12 @@ static void sched_tick_remote(struct work_struct *wo= rk) struct task_struct *curr =3D rq->curr; =20 if (cpu_online(cpu)) { + /* + * Since this is a remote tick for full dynticks mode, + * we are always sure that there is no proxy (only a + * single task is running). + */ + SCHED_WARN_ON(rq->curr !=3D rq_selected(rq)); update_rq_clock(rq); =20 if (!is_idle_task(curr)) { @@ -6685,6 +6695,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) } =20 next =3D pick_next_task(rq, prev, &rf); + rq_set_selected(rq, next); clear_tsk_need_resched(prev); clear_preempt_need_resched(); #ifdef CONFIG_SCHED_DEBUG @@ -7185,7 +7196,7 @@ void rt_mutex_setprio(struct task_struct *p, struct t= ask_struct *pi_task) =20 prev_class =3D p->sched_class; queued =3D task_on_rq_queued(p); - running =3D task_current(rq, p); + running =3D task_current_selected(rq, p); if (queued) dequeue_task(rq, p, queue_flag); if (running) @@ -7275,7 +7286,7 @@ void set_user_nice(struct task_struct *p, long nice) } =20 queued =3D task_on_rq_queued(p); - running =3D task_current(rq, p); + running =3D task_current_selected(rq, p); if (queued) dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); if (running) @@ -7868,7 +7879,7 @@ static int __sched_setscheduler(struct task_struct *p, } =20 queued =3D task_on_rq_queued(p); - running =3D task_current(rq, p); + running =3D task_current_selected(rq, p); if (queued) dequeue_task(rq, p, queue_flags); if (running) @@ -9295,6 +9306,7 @@ void __init init_idle(struct task_struct *idle, int c= pu) rcu_read_unlock(); =20 rq->idle =3D idle; + rq_set_selected(rq, idle); rcu_assign_pointer(rq->curr, idle); idle->on_rq =3D TASK_ON_RQ_QUEUED; #ifdef CONFIG_SMP @@ -9384,7 +9396,7 @@ void sched_setnuma(struct task_struct *p, int nid) =20 rq =3D task_rq_lock(p, &rf); queued =3D task_on_rq_queued(p); - running =3D task_current(rq, p); + running =3D task_current_selected(rq, p); =20 if (queued) dequeue_task(rq, p, DEQUEUE_SAVE); @@ -10489,7 +10501,7 @@ void sched_move_task(struct task_struct *tsk) =20 update_rq_clock(rq); =20 - running =3D task_current(rq, tsk); + running =3D task_current_selected(rq, tsk); queued =3D task_on_rq_queued(tsk); =20 if (queued) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 6140f1f51da1..9cf20f4ac5f9 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1150,7 +1150,7 @@ static enum hrtimer_restart dl_task_timer(struct hrti= mer *timer) #endif =20 enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); - if (dl_task(rq->curr)) + if (dl_task(rq_selected(rq))) wakeup_preempt_dl(rq, p, 0); else resched_curr(rq); @@ -1273,7 +1273,7 @@ static u64 grub_reclaim(u64 delta, struct rq *rq, str= uct sched_dl_entity *dl_se) */ static void update_curr_dl(struct rq *rq) { - struct task_struct *curr =3D rq->curr; + struct task_struct *curr =3D rq_selected(rq); struct sched_dl_entity *dl_se =3D &curr->dl; s64 delta_exec, scaled_delta_exec; int cpu =3D cpu_of(rq); @@ -1784,7 +1784,7 @@ static int find_later_rq(struct task_struct *task); static int select_task_rq_dl(struct task_struct *p, int cpu, int flags) { - struct task_struct *curr; + struct task_struct *curr, *selected; bool select_rq; struct rq *rq; =20 @@ -1795,6 +1795,7 @@ select_task_rq_dl(struct task_struct *p, int cpu, int= flags) =20 rcu_read_lock(); curr =3D READ_ONCE(rq->curr); /* unlocked access */ + selected =3D READ_ONCE(rq_selected(rq)); =20 /* * If we are dealing with a -deadline task, we must @@ -1805,9 +1806,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int= flags) * other hand, if it has a shorter deadline, we * try to make it stay here, it might be important. */ - select_rq =3D unlikely(dl_task(curr)) && + select_rq =3D unlikely(dl_task(selected)) && (curr->nr_cpus_allowed < 2 || - !dl_entity_preempt(&p->dl, &curr->dl)) && + !dl_entity_preempt(&p->dl, &selected->dl)) && p->nr_cpus_allowed > 1; =20 /* @@ -1870,7 +1871,7 @@ static void check_preempt_equal_dl(struct rq *rq, str= uct task_struct *p) * let's hope p can move out. */ if (rq->curr->nr_cpus_allowed =3D=3D 1 || - !cpudl_find(&rq->rd->cpudl, rq->curr, NULL)) + !cpudl_find(&rq->rd->cpudl, rq_selected(rq), NULL)) return; =20 /* @@ -1909,7 +1910,7 @@ static int balance_dl(struct rq *rq, struct task_stru= ct *p, struct rq_flags *rf) static void wakeup_preempt_dl(struct rq *rq, struct task_struct *p, int flags) { - if (dl_entity_preempt(&p->dl, &rq->curr->dl)) { + if (dl_entity_preempt(&p->dl, &rq_selected(rq)->dl)) { resched_curr(rq); return; } @@ -1919,7 +1920,7 @@ static void wakeup_preempt_dl(struct rq *rq, struct t= ask_struct *p, * In the unlikely case current and p have the same deadline * let us try to decide what's the best thing to do... */ - if ((p->dl.deadline =3D=3D rq->curr->dl.deadline) && + if ((p->dl.deadline =3D=3D rq_selected(rq)->dl.deadline) && !test_tsk_need_resched(rq->curr)) check_preempt_equal_dl(rq, p); #endif /* CONFIG_SMP */ @@ -1954,7 +1955,7 @@ static void set_next_task_dl(struct rq *rq, struct ta= sk_struct *p, bool first) if (hrtick_enabled_dl(rq)) start_hrtick_dl(rq, p); =20 - if (rq->curr->sched_class !=3D &dl_sched_class) + if (rq_selected(rq)->sched_class !=3D &dl_sched_class) update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0); =20 deadline_queue_push_tasks(rq); @@ -2268,8 +2269,8 @@ static int push_dl_task(struct rq *rq) * can move away, it makes sense to just reschedule * without going further in pushing next_task. */ - if (dl_task(rq->curr) && - dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) && + if (dl_task(rq_selected(rq)) && + dl_time_before(next_task->dl.deadline, rq_selected(rq)->dl.deadline) = && rq->curr->nr_cpus_allowed > 1) { resched_curr(rq); return 0; @@ -2394,7 +2395,7 @@ static void pull_dl_task(struct rq *this_rq) * deadline than the current task of its runqueue. */ if (dl_time_before(p->dl.deadline, - src_rq->curr->dl.deadline)) + rq_selected(src_rq)->dl.deadline)) goto skip; =20 if (is_migration_disabled(p)) { @@ -2435,9 +2436,9 @@ static void task_woken_dl(struct rq *rq, struct task_= struct *p) if (!task_on_cpu(rq, p) && !test_tsk_need_resched(rq->curr) && p->nr_cpus_allowed > 1 && - dl_task(rq->curr) && + dl_task(rq_selected(rq)) && (rq->curr->nr_cpus_allowed < 2 || - !dl_entity_preempt(&p->dl, &rq->curr->dl))) { + !dl_entity_preempt(&p->dl, &rq_selected(rq)->dl))) { push_dl_tasks(rq); } } @@ -2612,12 +2613,12 @@ static void switched_to_dl(struct rq *rq, struct ta= sk_struct *p) return; } =20 - if (rq->curr !=3D p) { + if (rq_selected(rq) !=3D p) { #ifdef CONFIG_SMP if (p->nr_cpus_allowed > 1 && rq->dl.overloaded) deadline_queue_push_tasks(rq); #endif - if (dl_task(rq->curr)) + if (dl_task(rq_selected(rq))) wakeup_preempt_dl(rq, p, 0); else resched_curr(rq); @@ -2646,7 +2647,7 @@ static void prio_changed_dl(struct rq *rq, struct tas= k_struct *p, if (!rq->dl.overloaded) deadline_queue_pull_task(rq); =20 - if (task_current(rq, p)) { + if (task_current_selected(rq, p)) { /* * If we now have a earlier deadline task than p, * then reschedule, provided p is still on this diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1251fd01a555..07216ea3ed53 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1157,7 +1157,7 @@ static s64 update_curr_se(struct rq *rq, struct sched= _entity *curr) */ s64 update_curr_common(struct rq *rq) { - struct task_struct *curr =3D rq->curr; + struct task_struct *curr =3D rq_selected(rq); s64 delta_exec; =20 delta_exec =3D update_curr_se(rq, &curr->se); @@ -1203,7 +1203,7 @@ static void update_curr(struct cfs_rq *cfs_rq) =20 static void update_curr_fair(struct rq *rq) { - update_curr(cfs_rq_of(&rq->curr->se)); + update_curr(cfs_rq_of(&rq_selected(rq)->se)); } =20 static inline void @@ -6611,7 +6611,7 @@ static void hrtick_start_fair(struct rq *rq, struct t= ask_struct *p) s64 delta =3D slice - ran; =20 if (delta < 0) { - if (task_current(rq, p)) + if (task_current_selected(rq, p)) resched_curr(rq); return; } @@ -6626,7 +6626,7 @@ static void hrtick_start_fair(struct rq *rq, struct t= ask_struct *p) */ static void hrtick_update(struct rq *rq) { - struct task_struct *curr =3D rq->curr; + struct task_struct *curr =3D rq_selected(rq); =20 if (!hrtick_enabled_fair(rq) || curr->sched_class !=3D &fair_sched_class) return; @@ -8235,7 +8235,7 @@ static void set_next_buddy(struct sched_entity *se) */ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p= , int wake_flags) { - struct task_struct *curr =3D rq->curr; + struct task_struct *curr =3D rq_selected(rq); struct sched_entity *se =3D &curr->se, *pse =3D &p->se; struct cfs_rq *cfs_rq =3D task_cfs_rq(curr); int next_buddy_marked =3D 0; @@ -8268,7 +8268,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, = struct task_struct *p, int * prevents us from potentially nominating it as a false LAST_BUDDY * below. */ - if (test_tsk_need_resched(curr)) + if (test_tsk_need_resched(rq->curr)) return; =20 /* Idle tasks are by definition preempted by non-idle tasks. */ @@ -9252,7 +9252,7 @@ static bool __update_blocked_others(struct rq *rq, bo= ol *done) * update_load_avg() can call cpufreq_update_util(). Make sure that RT, * DL and IRQ signals have been updated before updating CFS. */ - curr_class =3D rq->curr->sched_class; + curr_class =3D rq_selected(rq)->sched_class; =20 thermal_pressure =3D arch_scale_thermal_pressure(cpu_of(rq)); =20 @@ -12640,7 +12640,7 @@ prio_changed_fair(struct rq *rq, struct task_struct= *p, int oldprio) * our priority decreased, or if we are not currently running on * this runqueue and our priority is higher than the current's */ - if (task_current(rq, p)) { + if (task_current_selected(rq, p)) { if (p->prio > oldprio) resched_curr(rq); } else @@ -12743,7 +12743,7 @@ static void switched_to_fair(struct rq *rq, struct = task_struct *p) * kick off the schedule if running, otherwise just see * if we can still preempt the current task. */ - if (task_current(rq, p)) + if (task_current_selected(rq, p)) resched_curr(rq); else wakeup_preempt(rq, p, 0); diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 9cdea3ea47da..2682cec45aaa 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -530,7 +530,7 @@ static void dequeue_rt_entity(struct sched_rt_entity *r= t_se, unsigned int flags) =20 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq) { - struct task_struct *curr =3D rq_of_rt_rq(rt_rq)->curr; + struct task_struct *curr =3D rq_selected(rq_of_rt_rq(rt_rq)); struct rq *rq =3D rq_of_rt_rq(rt_rq); struct sched_rt_entity *rt_se; =20 @@ -1000,7 +1000,7 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt= _rq) */ static void update_curr_rt(struct rq *rq) { - struct task_struct *curr =3D rq->curr; + struct task_struct *curr =3D rq_selected(rq); struct sched_rt_entity *rt_se =3D &curr->rt; s64 delta_exec; =20 @@ -1545,7 +1545,7 @@ static int find_lowest_rq(struct task_struct *task); static int select_task_rq_rt(struct task_struct *p, int cpu, int flags) { - struct task_struct *curr; + struct task_struct *curr, *selected; struct rq *rq; bool test; =20 @@ -1557,6 +1557,7 @@ select_task_rq_rt(struct task_struct *p, int cpu, int= flags) =20 rcu_read_lock(); curr =3D READ_ONCE(rq->curr); /* unlocked access */ + selected =3D READ_ONCE(rq_selected(rq)); =20 /* * If the current task on @p's runqueue is an RT task, then @@ -1585,8 +1586,8 @@ select_task_rq_rt(struct task_struct *p, int cpu, int= flags) * systems like big.LITTLE. */ test =3D curr && - unlikely(rt_task(curr)) && - (curr->nr_cpus_allowed < 2 || curr->prio <=3D p->prio); + unlikely(rt_task(selected)) && + (curr->nr_cpus_allowed < 2 || selected->prio <=3D p->prio); =20 if (test || !rt_task_fits_capacity(p, cpu)) { int target =3D find_lowest_rq(p); @@ -1616,12 +1617,8 @@ select_task_rq_rt(struct task_struct *p, int cpu, in= t flags) =20 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p) { - /* - * Current can't be migrated, useless to reschedule, - * let's hope p can move out. - */ if (rq->curr->nr_cpus_allowed =3D=3D 1 || - !cpupri_find(&rq->rd->cpupri, rq->curr, NULL)) + !cpupri_find(&rq->rd->cpupri, rq_selected(rq), NULL)) return; =20 /* @@ -1664,7 +1661,9 @@ static int balance_rt(struct rq *rq, struct task_stru= ct *p, struct rq_flags *rf) */ static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int fl= ags) { - if (p->prio < rq->curr->prio) { + struct task_struct *curr =3D rq_selected(rq); + + if (p->prio < curr->prio) { resched_curr(rq); return; } @@ -1682,7 +1681,7 @@ static void wakeup_preempt_rt(struct rq *rq, struct t= ask_struct *p, int flags) * to move current somewhere else, making room for our non-migratable * task. */ - if (p->prio =3D=3D rq->curr->prio && !test_tsk_need_resched(rq->curr)) + if (p->prio =3D=3D curr->prio && !test_tsk_need_resched(rq->curr)) check_preempt_equal_prio(rq, p); #endif } @@ -1707,7 +1706,7 @@ static inline void set_next_task_rt(struct rq *rq, st= ruct task_struct *p, bool f * utilization. We only care of the case where we start to schedule a * rt task */ - if (rq->curr->sched_class !=3D &rt_sched_class) + if (rq_selected(rq)->sched_class !=3D &rt_sched_class) update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0); =20 rt_queue_push_tasks(rq); @@ -1988,6 +1987,7 @@ static struct task_struct *pick_next_pushable_task(st= ruct rq *rq) =20 BUG_ON(rq->cpu !=3D task_cpu(p)); BUG_ON(task_current(rq, p)); + BUG_ON(task_current_selected(rq, p)); BUG_ON(p->nr_cpus_allowed <=3D 1); =20 BUG_ON(!task_on_rq_queued(p)); @@ -2020,7 +2020,7 @@ static int push_rt_task(struct rq *rq, bool pull) * higher priority than current. If that's the case * just reschedule current. */ - if (unlikely(next_task->prio < rq->curr->prio)) { + if (unlikely(next_task->prio < rq_selected(rq)->prio)) { resched_curr(rq); return 0; } @@ -2375,7 +2375,7 @@ static void pull_rt_task(struct rq *this_rq) * p if it is lower in priority than the * current task on the run queue */ - if (p->prio < src_rq->curr->prio) + if (p->prio < rq_selected(src_rq)->prio) goto skip; =20 if (is_migration_disabled(p)) { @@ -2419,9 +2419,9 @@ static void task_woken_rt(struct rq *rq, struct task_= struct *p) bool need_to_push =3D !task_on_cpu(rq, p) && !test_tsk_need_resched(rq->curr) && p->nr_cpus_allowed > 1 && - (dl_task(rq->curr) || rt_task(rq->curr)) && + (dl_task(rq_selected(rq)) || rt_task(rq_selected(rq))) && (rq->curr->nr_cpus_allowed < 2 || - rq->curr->prio <=3D p->prio); + rq_selected(rq)->prio <=3D p->prio); =20 if (need_to_push) push_rt_tasks(rq); @@ -2505,7 +2505,7 @@ static void switched_to_rt(struct rq *rq, struct task= _struct *p) if (p->nr_cpus_allowed > 1 && rq->rt.overloaded) rt_queue_push_tasks(rq); #endif /* CONFIG_SMP */ - if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq))) + if (p->prio < rq_selected(rq)->prio && cpu_online(cpu_of(rq))) resched_curr(rq); } } @@ -2520,7 +2520,7 @@ prio_changed_rt(struct rq *rq, struct task_struct *p,= int oldprio) if (!task_on_rq_queued(p)) return; =20 - if (task_current(rq, p)) { + if (task_current_selected(rq, p)) { #ifdef CONFIG_SMP /* * If our priority decreases while running, we @@ -2546,7 +2546,7 @@ prio_changed_rt(struct rq *rq, struct task_struct *p,= int oldprio) * greater than the current running task * then reschedule. */ - if (p->prio < rq->curr->prio) + if (p->prio < rq_selected(rq)->prio) resched_curr(rq); } } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 3e0e4fc8734b..6ea1dfbe502a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -994,7 +994,10 @@ struct rq { */ unsigned int nr_uninterruptible; =20 - struct task_struct __rcu *curr; + struct task_struct __rcu *curr; /* Execution context */ +#ifdef CONFIG_SCHED_PROXY_EXEC + struct task_struct __rcu *curr_selected; /* Scheduling context (policy) */ +#endif struct task_struct *idle; struct task_struct *stop; unsigned long next_balance; @@ -1189,6 +1192,20 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #define raw_rq() raw_cpu_ptr(&runqueues) =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +#define rq_selected(rq) ((rq)->curr_selected) +static inline void rq_set_selected(struct rq *rq, struct task_struct *t) +{ + rcu_assign_pointer(rq->curr_selected, t); +} +#else +#define rq_selected(rq) ((rq)->curr) +static inline void rq_set_selected(struct rq *rq, struct task_struct *t) +{ + /* Do nothing */ +} +#endif + struct sched_group; #ifdef CONFIG_SCHED_CORE static inline struct cpumask *sched_group_span(struct sched_group *sg); @@ -2112,11 +2129,25 @@ static inline u64 global_rt_runtime(void) return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC; } =20 +/* + * Is p the current execution context? + */ static inline int task_current(struct rq *rq, struct task_struct *p) { return rq->curr =3D=3D p; } =20 +/* + * Is p the current scheduling context? + * + * Note that it might be the current execution context at the same time if + * rq->curr =3D=3D rq_selected() =3D=3D p. + */ +static inline int task_current_selected(struct rq *rq, struct task_struct = *p) +{ + return rq_selected(rq) =3D=3D p; +} + static inline int task_on_cpu(struct rq *rq, struct task_struct *p) { #ifdef CONFIG_SMP @@ -2280,7 +2311,7 @@ struct sched_class { =20 static inline void put_prev_task(struct rq *rq, struct task_struct *prev) { - WARN_ON_ONCE(rq->curr !=3D prev); + WARN_ON_ONCE(rq_selected(rq) !=3D prev); prev->sched_class->put_prev_task(rq, prev); } =20 --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9D473FBF9 for ; Wed, 20 Dec 2023 00:19:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Hdc7kpd0" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5e744f7ca3bso28795007b3.2 for ; Tue, 19 Dec 2023 16:19:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031558; x=1703636358; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=cuXcWz7no4J7hYPFBrTfbHGW+LQBOb7rSCL/XXuOMcE=; b=Hdc7kpd0JSlaT6HaqU305GT9p2q+6sERQ+Tawqr7rtKFHHnhymgsIXAPPxiGdO0uEQ wrWzuDOQvYyE8HJkwjxRJBGs/KBtvF5EHixfSqxgxg5v89+/VZCf3pVlZDLIoPLEYdyn xREssLNiBELIXorXgCF58uuECIqIBEuftfN1RndRJ3bBw06XoJadHxmzhA6cAVoonx7f yJib8bO1AKl8nykmM2DUWOIdhnOeLdknNbkyIkryeikF0o8w+1/6tbel3HCbeEVYGY85 GSx4Sp4pmsIBjblBsZqqOnJnZ7UxpwbNjuyEHEzdCfmn0D4kms5xZ/OjksFdsJwl77Bt MD6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031558; x=1703636358; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=cuXcWz7no4J7hYPFBrTfbHGW+LQBOb7rSCL/XXuOMcE=; b=I6ei6OQyHjjxoMH/m/jOJdvEtWqmRiAil5bPJbwkGqdOTA8kExAsloFQEqmoNX+CB8 A6XedcFbveylXpKLMCbqm1rG/ZfqLrTiO1CCQeEI67E7P/XXUwX8WfVxmdTDkNxyG5Mq HW3BmCiNOQFwR3c/u6MJ9d8hKLqDk8LEA5rNsj/bFcG3rooPH0QoKNf4qvspwN8J5S8u JFd1Oi7u74fJVrsAp0XEbg33yydlrXUFbPLq6vJoG9ksJeSzmimc2xKv3paMTX68ssBL h84mjjNCZ8ZyfG7pWJDiKZLiWgk2Qd+Qv5hj/65RnRAAw8ZPL/sPJ6nWUfV4iZhDdb0d PXRQ== X-Gm-Message-State: AOJu0YxJ+pzu4uY0QYWZ83Jiuw3TAI76oYpwVeUlp7hZiliycrRDGz6h XBd0zgbE+GWZ5KorFiz4Ena90SlerPSW/ndbsfwPvohCf1Ir3bb/eEGaZtKgJH2TIxWLHKT3yVD fNThN5cWWAZPFOfyucWvgLNgJXu8mR+Oyr7kZsCJL/jHa4CmEr70YjE34hdYTPz4fsWBOGjQ= X-Google-Smtp-Source: AGHT+IFk3luOh4aXdlgpR2eInNYC3gaeKH4418CKXXWcfADelNswhEGx3is/G7wUOm6QsIm4FJztvzongW7F X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:690c:f09:b0:5e6:27ee:67fb with SMTP id dc9-20020a05690c0f0900b005e627ee67fbmr1972577ywb.4.1703031558554; Tue, 19 Dec 2023 16:19:18 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:20 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-10-jstultz@google.com> Subject: [PATCH v7 09/23] sched: Fix runtime accounting w/ split exec & sched contexts From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The idea here is we want to charge the scheduler-context task's vruntime but charge the execution-context task's sum_exec_runtime. This way cputime accounting goes against the task actually running but vruntime accounting goes against the selected task so we get proper fairness. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- kernel/sched/fair.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 07216ea3ed53..085941db5bf1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1129,22 +1129,35 @@ static void update_tg_load_avg(struct cfs_rq *cfs_r= q) } #endif /* CONFIG_SMP */ =20 -static s64 update_curr_se(struct rq *rq, struct sched_entity *curr) +static s64 update_curr_se(struct rq *rq, struct sched_entity *se) { u64 now =3D rq_clock_task(rq); s64 delta_exec; =20 - delta_exec =3D now - curr->exec_start; + /* Calculate the delta from selected se */ + delta_exec =3D now - se->exec_start; if (unlikely(delta_exec <=3D 0)) return delta_exec; =20 - curr->exec_start =3D now; - curr->sum_exec_runtime +=3D delta_exec; + /* Update selected se's exec_start */ + se->exec_start =3D now; + if (entity_is_task(se)) { + struct task_struct *running =3D rq->curr; + /* + * If se is a task, we account the time against the running + * task, as w/ proxy-exec they may not be the same. + */ + running->se.exec_start =3D now; + running->se.sum_exec_runtime +=3D delta_exec; + } else { + /* If not task, account the time against se */ + se->sum_exec_runtime +=3D delta_exec; + } =20 if (schedstat_enabled()) { struct sched_statistics *stats; =20 - stats =3D __schedstats_from_se(curr); + stats =3D __schedstats_from_se(se); __schedstat_set(stats->exec_max, max(delta_exec, stats->exec_max)); } --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61DBC12B86 for ; Wed, 20 Dec 2023 00:19:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Tue, 19 Dec 2023 16:19:20 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:21 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-11-jstultz@google.com> Subject: [PATCH v7 10/23] sched: Split out __sched() deactivate task logic into a helper From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As we're going to re-use the deactivation logic, split it into a helper. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- v6: * Define function as static to avoid "no previous prototype" warnings as Reported-by: kernel test robot v7: * Rename state task_state to be more clear, as suggested by Metin Kaya --- kernel/sched/core.c | 66 +++++++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 29 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0ce34f5c0e0c..34acd80b6bd0 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6571,6 +6571,42 @@ pick_next_task(struct rq *rq, struct task_struct *pr= ev, struct rq_flags *rf) # define SM_MASK_PREEMPT SM_PREEMPT #endif =20 +static bool try_to_deactivate_task(struct rq *rq, struct task_struct *p, + unsigned long task_state) +{ + if (signal_pending_state(task_state, p)) { + WRITE_ONCE(p->__state, TASK_RUNNING); + } else { + p->sched_contributes_to_load =3D + (task_state & TASK_UNINTERRUPTIBLE) && + !(task_state & TASK_NOLOAD) && + !(task_state & TASK_FROZEN); + + if (p->sched_contributes_to_load) + rq->nr_uninterruptible++; + + /* + * __schedule() ttwu() + * prev_state =3D prev->state; if (p->on_rq && ...) + * if (prev_state) goto out; + * p->on_rq =3D 0; smp_acquire__after_ctrl_dep(); + * p->state =3D TASK_WAKING + * + * Where __schedule() and ttwu() have matching control dependencies. + * + * After this, schedule() must not care about p->state any more. + */ + deactivate_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); + + if (p->in_iowait) { + atomic_inc(&rq->nr_iowait); + delayacct_blkio_start(); + } + return true; + } + return false; +} + /* * __schedule() is the main scheduler function. * @@ -6662,35 +6698,7 @@ static void __sched notrace __schedule(unsigned int = sched_mode) */ prev_state =3D READ_ONCE(prev->__state); if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) { - if (signal_pending_state(prev_state, prev)) { - WRITE_ONCE(prev->__state, TASK_RUNNING); - } else { - prev->sched_contributes_to_load =3D - (prev_state & TASK_UNINTERRUPTIBLE) && - !(prev_state & TASK_NOLOAD) && - !(prev_state & TASK_FROZEN); - - if (prev->sched_contributes_to_load) - rq->nr_uninterruptible++; - - /* - * __schedule() ttwu() - * prev_state =3D prev->state; if (p->on_rq && ...) - * if (prev_state) goto out; - * p->on_rq =3D 0; smp_acquire__after_ctrl_dep(); - * p->state =3D TASK_WAKING - * - * Where __schedule() and ttwu() have matching control dependencies. - * - * After this, schedule() must not care about p->state any more. - */ - deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); - - if (prev->in_iowait) { - atomic_inc(&rq->nr_iowait); - delayacct_blkio_start(); - } - } + try_to_deactivate_task(rq, prev, prev_state); switch_count =3D &prev->nvcsw; } =20 --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C3D715ADB for ; Wed, 20 Dec 2023 00:19:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Tue, 19 Dec 2023 16:19:21 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:22 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-12-jstultz@google.com> Subject: [PATCH v7 11/23] sched: Add a initial sketch of the find_proxy_task() function From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a find_proxy_task() function which doesn't do much. When we select a blocked task to run, we will just deactivate it and pick again. The exception being if it has become unblocked after find_proxy_task() was called. Greatly simplified from patch by: Peter Zijlstra (Intel) Juri Lelli Valentin Schneider Connor O'Brien Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com [jstultz: Split out from larger proxy patch and simplified for review and testing.] Signed-off-by: John Stultz --- v5: * Split out from larger proxy patch v7: * Fixed unused function arguments, spelling nits, and tweaks for clarity, pointed out by Metin Kaya * Moved task_is_blocked() implementation to this patch where it is first used. Also drop unused arguments. Suggested by Metin Kaya. * Tweaks to make things easier to read, as suggested by Metin Kaya. * Rename proxy() to find_proxy_task() for clarity, and typo fixes suggested by Metin Kaya * Fix build warning Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202311081028.yDLmCWgr-lkp@i= ntel.com/ --- kernel/sched/core.c | 87 ++++++++++++++++++++++++++++++++++++++++++-- kernel/sched/rt.c | 19 +++++++++- kernel/sched/sched.h | 15 ++++++++ 3 files changed, 115 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 34acd80b6bd0..12f5a0618328 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6572,11 +6572,11 @@ pick_next_task(struct rq *rq, struct task_struct *p= rev, struct rq_flags *rf) #endif =20 static bool try_to_deactivate_task(struct rq *rq, struct task_struct *p, - unsigned long task_state) + unsigned long task_state, bool deactivate_cond) { if (signal_pending_state(task_state, p)) { WRITE_ONCE(p->__state, TASK_RUNNING); - } else { + } else if (deactivate_cond) { p->sched_contributes_to_load =3D (task_state & TASK_UNINTERRUPTIBLE) && !(task_state & TASK_NOLOAD) && @@ -6607,6 +6607,73 @@ static bool try_to_deactivate_task(struct rq *rq, st= ruct task_struct *p, return false; } =20 +#ifdef CONFIG_SCHED_PROXY_EXEC + +static bool proxy_deactivate(struct rq *rq, struct task_struct *next) +{ + unsigned long state =3D READ_ONCE(next->__state); + + /* Don't deactivate if the state has been changed to TASK_RUNNING */ + if (state =3D=3D TASK_RUNNING) + return false; + if (!try_to_deactivate_task(rq, next, state, true)) + return false; + put_prev_task(rq, next); + rq_set_selected(rq, rq->idle); + resched_curr(rq); + return true; +} + +/* + * Initial simple proxy that just returns the task if it's waking + * or deactivates the blocked task so we can pick something that + * isn't blocked. + */ +static struct task_struct * +find_proxy_task(struct rq *rq, struct task_struct *next, struct rq_flags *= rf) +{ + struct task_struct *ret =3D NULL; + struct task_struct *p =3D next; + struct mutex *mutex; + + mutex =3D p->blocked_on; + /* Something changed in the chain, so pick again */ + if (!mutex) + return NULL; + /* + * By taking mutex->wait_lock we hold off concurrent mutex_unlock() + * and ensure @owner sticks around. + */ + raw_spin_lock(&mutex->wait_lock); + raw_spin_lock(&p->blocked_lock); + + /* Check again that p is blocked with blocked_lock held */ + if (!task_is_blocked(p) || mutex !=3D p->blocked_on) { + /* + * Something changed in the blocked_on chain and + * we don't know if only at this level. So, let's + * just bail out completely and let __schedule + * figure things out (pick_again loop). + */ + goto out; + } + + if (!proxy_deactivate(rq, next)) + ret =3D p; +out: + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + return ret; +} +#else /* SCHED_PROXY_EXEC */ +static struct task_struct * +find_proxy_task(struct rq *rq, struct task_struct *next, struct rq_flags *= rf) +{ + BUG(); // This should never be called in the !PROXY case + return next; +} +#endif /* SCHED_PROXY_EXEC */ + /* * __schedule() is the main scheduler function. * @@ -6698,12 +6765,24 @@ static void __sched notrace __schedule(unsigned int= sched_mode) */ prev_state =3D READ_ONCE(prev->__state); if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) { - try_to_deactivate_task(rq, prev, prev_state); + try_to_deactivate_task(rq, prev, prev_state, + !task_is_blocked(prev)); switch_count =3D &prev->nvcsw; } =20 - next =3D pick_next_task(rq, prev, &rf); +pick_again: + next =3D pick_next_task(rq, rq_selected(rq), &rf); rq_set_selected(rq, next); + if (unlikely(task_is_blocked(next))) { + next =3D find_proxy_task(rq, next, &rf); + if (!next) { + rq_unpin_lock(rq, &rf); + __balance_callbacks(rq); + rq_repin_lock(rq, &rf); + goto pick_again; + } + } + clear_tsk_need_resched(prev); clear_preempt_need_resched(); #ifdef CONFIG_SCHED_DEBUG diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 2682cec45aaa..81cd22eaa6dc 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1491,8 +1491,19 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p= , int flags) =20 enqueue_rt_entity(rt_se, flags); =20 - if (!task_current(rq, p) && p->nr_cpus_allowed > 1) - enqueue_pushable_task(rq, p); + /* + * Current can't be pushed away. Selected is tied to current, + * so don't push it either. + */ + if (task_current(rq, p) || task_current_selected(rq, p)) + return; + /* + * Pinned tasks can't be pushed. + */ + if (p->nr_cpus_allowed =3D=3D 1) + return; + + enqueue_pushable_task(rq, p); } =20 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flag= s) @@ -1779,6 +1790,10 @@ static void put_prev_task_rt(struct rq *rq, struct t= ask_struct *p) =20 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1); =20 + /* Avoid marking selected as pushable */ + if (task_current_selected(rq, p)) + return; + /* * The previous task needs to be made eligible for pushing * if it is still active diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 6ea1dfbe502a..765ba10661de 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2148,6 +2148,21 @@ static inline int task_current_selected(struct rq *r= q, struct task_struct *p) return rq_selected(rq) =3D=3D p; } =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +static inline bool task_is_blocked(struct task_struct *p) +{ + if (!sched_proxy_exec()) + return false; + + return !!p->blocked_on && p->blocked_on_state !=3D BO_RUNNABLE; +} +#else /* !SCHED_PROXY_EXEC */ +static inline bool task_is_blocked(struct task_struct *p) +{ + return false; +} +#endif /* SCHED_PROXY_EXEC */ + static inline int task_on_cpu(struct rq *rq, struct task_struct *p) { #ifdef CONFIG_SMP --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D4E1168C4 for ; Wed, 20 Dec 2023 00:19:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CN3eC1b8" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-28b6a78a164so3269242a91.0 for ; Tue, 19 Dec 2023 16:19:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031563; x=1703636363; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=WJZ0zBDHStU6K3+8MFmMAIsVcwSpztLmjKA4OaYGSSc=; b=CN3eC1b8cDs50wBw0TKGRLWUljQS7QAHezN8cauNxoTPio+leTvL9ng2q9JkHFUzyc qU5+8QZiu6FnH94cr6H/iWm4HS7Vtr7bse5vFSlYXvtoPRsDmjTxPjxEMHUYWTWmm1YE 4AxW7Ao8DLaGPwlHL/dnUW/YiFtfSyHssUQbwfVuaaXEJSRT2Kcs5Mde/n7oAgzQkzQJ O9XU46GssCRtleqt/+pxewzRZn6t7985edCRsBc7n3AG1DR8W1I9QkvsaYFiz5NutTmr AJ1RVwxLg4zLR5qnTB2yFR5zjCecmJrQ59nQ5wD9PogSFgcCpIwWRHcAs+x1hamBCc0a mE6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031563; x=1703636363; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=WJZ0zBDHStU6K3+8MFmMAIsVcwSpztLmjKA4OaYGSSc=; b=t2v+jI2+WVBFBnLqsC9ckpKLwc70HxHj3b/TS0jwpXonkDsE5yCDWgJfVaXz2PJK9W 6SbKvON4T2CcJPW6qHcgJBwgfzoL0IUKJboHadQIU8ZDVW/LXh2fU2jIFJ/I0h+urlox K6jqGR8nOTjU0S76wD9KUSyf0sWkv20p1LLFnrbyZTxuIy8AHZhBszRjdZbwcKOoL1fq pmSuIFulypB/9VsTacntmUspWy21ZoKLaT4cBJ2ouWfNuUSpLDe+3ngEwtI4Ip67pr2R Sc2iCchzBd5454EC3quKL46SdbVPUD7msgkFmD6Ibg4eADgwvigRlTbssh3QT3DRIRIE u1Fg== X-Gm-Message-State: AOJu0YykkLqbhPhY6kQR21RVprBrZU2BUBORyrSn6mlZhn6iYbp1THfD X5SFtOKC+jR+bMjewdPZVI7ATJFoE4CR76Pw5PE47OIjw+xXtfZ7gBIv4ojtyfptJVfqTYNJBHy 9SnaoX7Q1WyDOXKJ6EdB9Ey0WPLoWemPhIRNiHHrlLjWS+dGzCgJYIsNWjClpFvARNn184oo= X-Google-Smtp-Source: AGHT+IGzRywgAhtbebax+3YKrye4FWAcGffQ0efj4jXwyF8sgDKKZZBDdhKiOBOPTqQRlXM+IXL7ywPIuyBM X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a17:90b:1b09:b0:28b:4d36:522 with SMTP id nu9-20020a17090b1b0900b0028b4d360522mr884613pjb.8.1703031563577; Tue, 19 Dec 2023 16:19:23 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:23 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-13-jstultz@google.com> Subject: [PATCH v7 12/23] sched: Fix proxy/current (push,pull)ability From: John Stultz To: LKML Cc: Valentin Schneider , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Valentin Schneider Proxy execution forms atomic pairs of tasks: The selected task (scheduling context) and a proxy (execution context). The selected task, along with the rest of the blocked chain, follows the proxy wrt CPU placement. They can be the same task, in which case push/pull doesn't need any modification. When they are different, however, FIFO1 & FIFO42: ,-> RT42 | | blocked-on | v blocked_donor | mutex | | owner | v `-- RT1 RT1 RT42 CPU0 CPU1 ^ ^ | | overloaded !overloaded rq prio =3D 42 rq prio =3D 0 RT1 is eligible to be pushed to CPU1, but should that happen it will "carry" RT42 along. Clearly here neither RT1 nor RT42 must be seen as push/pullable. Unfortunately, only the selected task is usually dequeued from the rq, and the proxy'ed execution context (rq->curr) remains on the rq. This can cause RT1 to be selected for migration from logic like the rt pushable_list. This patch adds a dequeue/enqueue cycle on the proxy task before __schedule returns, which allows the sched class logic to avoid adding the now current task to the pushable_list. Furthermore, tasks becoming blocked on a mutex don't need an explicit dequeue/enqueue cycle to be made (push/pull)able: they have to be running to block on a mutex, thus they will eventually hit put_prev_task(). XXX: pinned tasks becoming unblocked should be removed from the push/pull lists, but those don't get to see __schedule() straight away. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien Signed-off-by: John Stultz --- v3: * Tweaked comments & commit message v5: * Minor simplifications to utilize the fix earlier in the patch series. * Rework the wording of the commit message to match selected/ proxy terminology and expand a bit to make it more clear how it works. v6: * Droped now-unused proxied value, to be re-added later in the series when it is used, as caught by Dietmar v7: * Unused function argument fixup * Commit message nit pointed out by Metin Kaya * Droped unproven unlikely() and use sched_proxy_exec() in proxy_tag_curr, suggested by Metin Kaya --- kernel/sched/core.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 12f5a0618328..f6bf3b62194c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6674,6 +6674,23 @@ find_proxy_task(struct rq *rq, struct task_struct *n= ext, struct rq_flags *rf) } #endif /* SCHED_PROXY_EXEC */ =20 +static inline void proxy_tag_curr(struct rq *rq, struct task_struct *next) +{ + if (sched_proxy_exec()) { + /* + * pick_next_task() calls set_next_task() on the selected task + * at some point, which ensures it is not push/pullable. + * However, the selected task *and* the ,mutex owner form an + * atomic pair wrt push/pull. + * + * Make sure owner is not pushable. Unfortunately we can only + * deal with that by means of a dequeue/enqueue cycle. :-/ + */ + dequeue_task(rq, next, DEQUEUE_NOCLOCK | DEQUEUE_SAVE); + enqueue_task(rq, next, ENQUEUE_NOCLOCK | ENQUEUE_RESTORE); + } +} + /* * __schedule() is the main scheduler function. * @@ -6796,6 +6813,10 @@ static void __sched notrace __schedule(unsigned int = sched_mode) * changes to task_struct made by pick_next_task(). */ RCU_INIT_POINTER(rq->curr, next); + + if (!task_current_selected(rq, next)) + proxy_tag_curr(rq, next); + /* * The membarrier system call requires each architecture * to have a full memory barrier after updating @@ -6820,6 +6841,10 @@ static void __sched notrace __schedule(unsigned int = sched_mode) /* Also unlocks the rq: */ rq =3D context_switch(rq, prev, next, &rf); } else { + /* In case next was already curr but just got blocked_donor*/ + if (!task_current_selected(rq, next)) + proxy_tag_curr(rq, next); + rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq); --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3706613FE4 for ; Wed, 20 Dec 2023 00:19:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KSb7Bdg1" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-28b99b7fbfaso153628a91.1 for ; Tue, 19 Dec 2023 16:19:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031566; x=1703636366; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=u8WgaqIXkyAFx0G/RhAV46UCF+hdVqbhGhJLGicpbSA=; b=KSb7Bdg1nLi8JOy4ShJ8c+H8VOwu7np0TDTJhmfDKdjdQxy8vuu4bKxq7jY8kAg0w2 i/MOKl/iT9GdPAbvopQhYSMeFoD3XJtKt6IoBFrjU5Y1Ea+oIwRdXPcPbwbUfuuYfBJH asLstLvuC5jdjqg9QpmiXFqAZ1wq1Vwzso+lcNV9F+Q36Jpl1eDYWWa+x7RQoKgl88Uu +7tQfPPTW1yIBMSTdPDUeBn8BKNIOIHje+1+k289Hrg0n65SxzLXX3nATxb7wJJJhsmr QKJ3eC2znxBvkHDZ8tPss3Dnpv9mSI43+Gn0xA/xi1xDZHuFPaGRpmcKVDrUJ7GImVqr O6WQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031566; x=1703636366; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=u8WgaqIXkyAFx0G/RhAV46UCF+hdVqbhGhJLGicpbSA=; b=PzuL2J8CUIqGiDgOorvadTiO8MchzCwHHp6GTqkkRQcgXM358GUvbmDJzFNLwENUK+ rNorMRziBnVeMx6ldbo39u28rH9Dy3Fmbftu1tBe5xGUIX/4EmJ312FhyBOzAy5RgzU2 QQefDRc+0x/ho2d4egwOJ1+8Hd5hhgeTT9W/d89wLKsiwG5LXtVqBspGgzEh4y1qFOKR tK/yl8KBtK22f4D7eIzV+OF8gBR9Hhm2EbFVD87nbinKJHxeldjdlFmgv9/cTyGSpFe0 1HWzxK8HAF8BFOidqI1B3KPGudIwcJz3HAbeGM3Mbjgwyj/Q2iVp5ZIBd4pTAbru/20y d5jg== X-Gm-Message-State: AOJu0YyXB8uwBH3+/8q4wP2APvjnBe1gmP2gHF6BiUGhF+CjQAy0TZlW 20TgALpfhetrJWkIm45tsgR0+yJXo/iHm066Y6evVu/XtSraSXcmwO4y41wM8urcembKvzO7OzQ izrrgp6jloDRN61lhnxIQqijY53cBiToGXwuvIfnRNLSGNapwv8OC0Mev15bDgMQma67Qbvk= X-Google-Smtp-Source: AGHT+IHMOrzz5lb5qZb/T0Au2mJqoHi+nVVcxaq0EWc8u/KWDpXXnVS48h6LYWQ4iSm202Jin2lpRujCZDqQ X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a17:90b:1c11:b0:28b:c540:e83 with SMTP id oc17-20020a17090b1c1100b0028bc5400e83mr181283pjb.0.1703031565469; Tue, 19 Dec 2023 16:19:25 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:24 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-14-jstultz@google.com> Subject: [PATCH v7 13/23] sched: Start blocked_on chain processing in find_proxy_task() From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Start to flesh out the real find_proxy_task() implementation, but avoid the migration cases for now, in those cases just deactivate the selected task and pick again. To ensure the selected task or other blocked tasks in the chain aren't migrated away while we're running the proxy, this patch also tweaks CFS logic to avoid migrating selected or mutex blocked tasks. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien [jstultz: This change was split out from the larger proxy patch] Signed-off-by: John Stultz --- v5: * Split this out from larger proxy patch v7: * Minor refactoring of core find_proxy_task() function * Minor spelling and corrections suggested by Metin Kaya * Dropped an added BUG_ON that was frequently tripped * Minor commit message tweaks from Metin Kaya --- kernel/sched/core.c | 154 +++++++++++++++++++++++++++++++++++++------- kernel/sched/fair.c | 9 ++- 2 files changed, 137 insertions(+), 26 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f6bf3b62194c..42e25bbdfe6b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -94,6 +94,7 @@ #include "../workqueue_internal.h" #include "../../io_uring/io-wq.h" #include "../smpboot.h" +#include "../locking/mutex.h" =20 EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu); EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask); @@ -6609,6 +6610,15 @@ static bool try_to_deactivate_task(struct rq *rq, st= ruct task_struct *p, =20 #ifdef CONFIG_SCHED_PROXY_EXEC =20 +static inline struct task_struct * +proxy_resched_idle(struct rq *rq, struct task_struct *next) +{ + put_prev_task(rq, next); + rq_set_selected(rq, rq->idle); + set_tsk_need_resched(rq->idle); + return rq->idle; +} + static bool proxy_deactivate(struct rq *rq, struct task_struct *next) { unsigned long state =3D READ_ONCE(next->__state); @@ -6618,48 +6628,138 @@ static bool proxy_deactivate(struct rq *rq, struct= task_struct *next) return false; if (!try_to_deactivate_task(rq, next, state, true)) return false; - put_prev_task(rq, next); - rq_set_selected(rq, rq->idle); - resched_curr(rq); + proxy_resched_idle(rq, next); return true; } =20 /* - * Initial simple proxy that just returns the task if it's waking - * or deactivates the blocked task so we can pick something that - * isn't blocked. + * Find who @next (currently blocked on a mutex) can proxy for. + * + * Follow the blocked-on relation: + * task->blocked_on -> mutex->owner -> task... + * + * Lock order: + * + * p->pi_lock + * rq->lock + * mutex->wait_lock + * p->blocked_lock + * + * Returns the task that is going to be used as execution context (the one + * that is actually going to be put to run on cpu_of(rq)). */ static struct task_struct * find_proxy_task(struct rq *rq, struct task_struct *next, struct rq_flags *= rf) { + struct task_struct *owner =3D NULL; struct task_struct *ret =3D NULL; - struct task_struct *p =3D next; + struct task_struct *p; struct mutex *mutex; + int this_cpu =3D cpu_of(rq); =20 - mutex =3D p->blocked_on; - /* Something changed in the chain, so pick again */ - if (!mutex) - return NULL; /* - * By taking mutex->wait_lock we hold off concurrent mutex_unlock() - * and ensure @owner sticks around. + * Follow blocked_on chain. + * + * TODO: deadlock detection */ - raw_spin_lock(&mutex->wait_lock); - raw_spin_lock(&p->blocked_lock); + for (p =3D next; task_is_blocked(p); p =3D owner) { + mutex =3D p->blocked_on; + /* Something changed in the chain, so pick again */ + if (!mutex) + return NULL; =20 - /* Check again that p is blocked with blocked_lock held */ - if (!task_is_blocked(p) || mutex !=3D p->blocked_on) { /* - * Something changed in the blocked_on chain and - * we don't know if only at this level. So, let's - * just bail out completely and let __schedule - * figure things out (pick_again loop). + * By taking mutex->wait_lock we hold off concurrent mutex_unlock() + * and ensure @owner sticks around. */ - goto out; + raw_spin_lock(&mutex->wait_lock); + raw_spin_lock(&p->blocked_lock); + + /* Check again that p is blocked with blocked_lock held */ + if (mutex !=3D p->blocked_on) { + /* + * Something changed in the blocked_on chain and + * we don't know if only at this level. So, let's + * just bail out completely and let __schedule + * figure things out (pick_again loop). + */ + goto out; + } + + owner =3D __mutex_owner(mutex); + if (!owner) { + ret =3D p; + goto out; + } + + if (task_cpu(owner) !=3D this_cpu) { + /* XXX Don't handle migrations yet */ + if (!proxy_deactivate(rq, next)) + ret =3D next; + goto out; + } + + if (task_on_rq_migrating(owner)) { + /* + * One of the chain of mutex owners is currently migrating to this + * CPU, but has not yet been enqueued because we are holding the + * rq lock. As a simple solution, just schedule rq->idle to give + * the migration a chance to complete. Much like the migrate_task + * case we should end up back in proxy(), this time hopefully with + * all relevant tasks already enqueued. + */ + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + return proxy_resched_idle(rq, next); + } + + if (!owner->on_rq) { + /* XXX Don't handle blocked owners yet */ + if (!proxy_deactivate(rq, next)) + ret =3D next; + goto out; + } + + if (owner =3D=3D p) { + /* + * It's possible we interleave with mutex_unlock like: + * + * lock(&rq->lock); + * find_proxy_task() + * mutex_unlock() + * lock(&wait_lock); + * next(owner) =3D current->blocked_donor; + * unlock(&wait_lock); + * + * wake_up_q(); + * ... + * ttwu_runnable() + * __task_rq_lock() + * lock(&wait_lock); + * owner =3D=3D p + * + * Which leaves us to finish the ttwu_runnable() and make it go. + * + * So schedule rq->idle so that ttwu_runnable can get the rq lock + * and mark owner as running. + */ + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + return proxy_resched_idle(rq, next); + } + + /* + * OK, now we're absolutely sure @owner is not blocked _and_ + * on this rq, therefore holding @rq->lock is sufficient to + * guarantee its existence, as per ttwu_remote(). + */ + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); } =20 - if (!proxy_deactivate(rq, next)) - ret =3D p; + WARN_ON_ONCE(owner && !owner->on_rq); + return owner; + out: raw_spin_unlock(&p->blocked_lock); raw_spin_unlock(&mutex->wait_lock); @@ -6738,6 +6838,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) struct rq_flags rf; struct rq *rq; int cpu; + bool preserve_need_resched =3D false; =20 cpu =3D smp_processor_id(); rq =3D cpu_rq(cpu); @@ -6798,9 +6899,12 @@ static void __sched notrace __schedule(unsigned int = sched_mode) rq_repin_lock(rq, &rf); goto pick_again; } + if (next =3D=3D rq->idle && prev =3D=3D rq->idle) + preserve_need_resched =3D true; } =20 - clear_tsk_need_resched(prev); + if (!preserve_need_resched) + clear_tsk_need_resched(prev); clear_preempt_need_resched(); #ifdef CONFIG_SCHED_DEBUG rq->last_seen_need_resched_ns =3D 0; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 085941db5bf1..954b41e5b7df 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8905,6 +8905,9 @@ int can_migrate_task(struct task_struct *p, struct lb= _env *env) if (kthread_is_per_cpu(p)) return 0; =20 + if (task_is_blocked(p)) + return 0; + if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) { int cpu; =20 @@ -8941,7 +8944,8 @@ int can_migrate_task(struct task_struct *p, struct lb= _env *env) /* Record that we found at least one task that could run on dst_cpu */ env->flags &=3D ~LBF_ALL_PINNED; =20 - if (task_on_cpu(env->src_rq, p)) { + if (task_on_cpu(env->src_rq, p) || + task_current_selected(env->src_rq, p)) { schedstat_inc(p->stats.nr_failed_migrations_running); return 0; } @@ -8980,6 +8984,9 @@ static void detach_task(struct task_struct *p, struct= lb_env *env) { lockdep_assert_rq_held(env->src_rq); =20 + BUG_ON(task_current(env->src_rq, p)); + BUG_ON(task_current_selected(env->src_rq, p)); + deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK); set_task_cpu(p, env->dst_cpu); } --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 518151C6B8 for ; Wed, 20 Dec 2023 00:19:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZWeesYVB" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dbd980d774dso616181276.2 for ; Tue, 19 Dec 2023 16:19:28 -0800 (PST) DKIM-Signature: v=1; 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Tue, 19 Dec 2023 16:19:27 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:25 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-15-jstultz@google.com> Subject: [PATCH v7 14/23] sched: Handle blocked-waiter migration (and return migration) From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add logic to handle migrating a blocked waiter to a remote cpu where the lock owner is runnable. Additionally, as the blocked task may not be able to run on the remote cpu, add logic to handle return migration once the waiting task is given the mutex. Because tasks may get migrated to where they cannot run, this patch also modifies the scheduling classes to avoid sched class migrations on mutex blocked tasks, leaving proxy() to do the migrations and return migrations. This was split out from the larger proxy patch, and significantly reworked. Credits for the original patch go to: Peter Zijlstra (Intel) Juri Lelli Valentin Schneider Connor O'Brien Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- v6: * Integrated sched_proxy_exec() check in proxy_return_migration() * Minor cleanups to diff * Unpin the rq before calling __balance_callbacks() * Tweak proxy migrate to migrate deeper task in chain, to avoid tasks pingponging between rqs v7: * Fixup for unused function arguments * Switch from that_rq -> target_rq, other minor tweaks, and typo fixes suggested by Metin Kaya * Switch back to doing return migration in the ttwu path, which avoids nasty lock juggling and performance issues * Fixes for UP builds --- kernel/sched/core.c | 161 ++++++++++++++++++++++++++++++++++++++-- kernel/sched/deadline.c | 2 +- kernel/sched/fair.c | 4 +- kernel/sched/rt.c | 9 ++- 4 files changed, 164 insertions(+), 12 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 42e25bbdfe6b..55dc2a3b7e46 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2981,8 +2981,15 @@ static int affine_move_task(struct rq *rq, struct ta= sk_struct *p, struct rq_flag struct set_affinity_pending my_pending =3D { }, *pending =3D NULL; bool stop_pending, complete =3D false; =20 - /* Can the task run on the task's current CPU? If so, we're done */ - if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) { + /* + * Can the task run on the task's current CPU? If so, we're done + * + * We are also done if the task is selected, boosting a lock- + * holding proxy, (and potentially has been migrated outside its + * current or previous affinity mask) + */ + if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask) || + (task_current_selected(rq, p) && !task_current(rq, p))) { struct task_struct *push_task =3D NULL; =20 if ((flags & SCA_MIGRATE_ENABLE) && @@ -3778,6 +3785,39 @@ static inline void ttwu_do_wakeup(struct task_struct= *p) trace_sched_wakeup(p); } =20 +#ifdef CONFIG_SMP +static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p) +{ + if (!sched_proxy_exec()) + return false; + + if (task_current(rq, p)) + return false; + + if (p->blocked_on && p->blocked_on_state =3D=3D BO_WAKING) { + raw_spin_lock(&p->blocked_lock); + if (!is_cpu_allowed(p, cpu_of(rq))) { + if (task_current_selected(rq, p)) { + put_prev_task(rq, p); + rq_set_selected(rq, rq->idle); + } + deactivate_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); + resched_curr(rq); + raw_spin_unlock(&p->blocked_lock); + return true; + } + resched_curr(rq); + raw_spin_unlock(&p->blocked_lock); + } + return false; +} +#else /* !CONFIG_SMP */ +static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p) +{ + return false; +} +#endif /*CONFIG_SMP */ + static void ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, struct rq_flags *rf) @@ -3870,9 +3910,12 @@ static int ttwu_runnable(struct task_struct *p, int = wake_flags) update_rq_clock(rq); wakeup_preempt(rq, p, wake_flags); } + if (proxy_needs_return(rq, p)) + goto out; ttwu_do_wakeup(p); ret =3D 1; } +out: __task_rq_unlock(rq, &rf); =20 return ret; @@ -4231,6 +4274,7 @@ int try_to_wake_up(struct task_struct *p, unsigned in= t state, int wake_flags) int cpu, success =3D 0; =20 if (p =3D=3D current) { + WARN_ON(task_is_blocked(p)); /* * We're waking current, this means 'p->on_rq' and 'task_cpu(p) * =3D=3D smp_processor_id()'. Together this means we can special @@ -6632,6 +6676,91 @@ static bool proxy_deactivate(struct rq *rq, struct t= ask_struct *next) return true; } =20 +#ifdef CONFIG_SMP +/* + * If the blocked-on relationship crosses CPUs, migrate @p to the + * owner's CPU. + * + * This is because we must respect the CPU affinity of execution + * contexts (owner) but we can ignore affinity for scheduling + * contexts (@p). So we have to move scheduling contexts towards + * potential execution contexts. + * + * Note: The owner can disappear, but simply migrate to @target_cpu + * and leave that CPU to sort things out. + */ +static struct task_struct * +proxy_migrate_task(struct rq *rq, struct rq_flags *rf, + struct task_struct *p, int target_cpu) +{ + struct rq *target_rq; + int wake_cpu; + + lockdep_assert_rq_held(rq); + target_rq =3D cpu_rq(target_cpu); + + /* + * Since we're going to drop @rq, we have to put(@rq_selected) first, + * otherwise we have a reference that no longer belongs to us. Use + * @rq->idle to fill the void and make the next pick_next_task() + * invocation happy. + * + * CPU0 CPU1 + * + * B mutex_lock(X) + * + * A mutex_lock(X) <- B + * A __schedule() + * A pick->A + * A proxy->B + * A migrate A to CPU1 + * B mutex_unlock(X) -> A + * B __schedule() + * B pick->A + * B switch_to (A) + * A ... does stuff + * A ... is still running here + * + * * BOOM * + */ + put_prev_task(rq, rq_selected(rq)); + rq_set_selected(rq, rq->idle); + set_next_task(rq, rq_selected(rq)); + WARN_ON(p =3D=3D rq->curr); + + wake_cpu =3D p->wake_cpu; + deactivate_task(rq, p, 0); + set_task_cpu(p, target_cpu); + /* + * Preserve p->wake_cpu, such that we can tell where it + * used to run later. + */ + p->wake_cpu =3D wake_cpu; + + rq_unpin_lock(rq, rf); + __balance_callbacks(rq); + + raw_spin_rq_unlock(rq); + raw_spin_rq_lock(target_rq); + + activate_task(target_rq, p, 0); + wakeup_preempt(target_rq, p, 0); + + raw_spin_rq_unlock(target_rq); + raw_spin_rq_lock(rq); + rq_repin_lock(rq, rf); + + return NULL; /* Retry task selection on _this_ CPU. */ +} +#else /* !CONFIG_SMP */ +static struct task_struct * +proxy_migrate_task(struct rq *rq, struct rq_flags *rf, + struct task_struct *p, int target_cpu) +{ + return NULL; +} +#endif /* CONFIG_SMP */ + /* * Find who @next (currently blocked on a mutex) can proxy for. * @@ -6654,8 +6783,11 @@ find_proxy_task(struct rq *rq, struct task_struct *n= ext, struct rq_flags *rf) struct task_struct *owner =3D NULL; struct task_struct *ret =3D NULL; struct task_struct *p; + int cur_cpu, target_cpu; struct mutex *mutex; - int this_cpu =3D cpu_of(rq); + bool curr_in_chain =3D false; + + cur_cpu =3D cpu_of(rq); =20 /* * Follow blocked_on chain. @@ -6686,17 +6818,27 @@ find_proxy_task(struct rq *rq, struct task_struct *= next, struct rq_flags *rf) goto out; } =20 + if (task_current(rq, p)) + curr_in_chain =3D true; + owner =3D __mutex_owner(mutex); if (!owner) { ret =3D p; goto out; } =20 - if (task_cpu(owner) !=3D this_cpu) { - /* XXX Don't handle migrations yet */ - if (!proxy_deactivate(rq, next)) - ret =3D next; - goto out; + if (task_cpu(owner) !=3D cur_cpu) { + target_cpu =3D task_cpu(owner); + /* + * @owner can disappear, simply migrate to @target_cpu and leave that C= PU + * to sort things out. + */ + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + if (curr_in_chain) + return proxy_resched_idle(rq, next); + + return proxy_migrate_task(rq, rf, p, target_cpu); } =20 if (task_on_rq_migrating(owner)) { @@ -6999,6 +7141,9 @@ static inline void sched_submit_work(struct task_stru= ct *tsk) */ SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT); =20 + if (task_is_blocked(tsk)) + return; + /* * If we are going to sleep and we have plugged IO queued, * make sure to submit it to avoid deadlocks. diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 9cf20f4ac5f9..4f998549ea74 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1705,7 +1705,7 @@ static void enqueue_task_dl(struct rq *rq, struct tas= k_struct *p, int flags) =20 enqueue_dl_entity(&p->dl, flags); =20 - if (!task_current(rq, p) && p->nr_cpus_allowed > 1) + if (!task_current(rq, p) && p->nr_cpus_allowed > 1 && !task_is_blocked(p)) enqueue_pushable_dl_task(rq, p); } =20 diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 954b41e5b7df..8e3f118f6d6e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8372,7 +8372,9 @@ pick_next_task_fair(struct rq *rq, struct task_struct= *prev, struct rq_flags *rf goto idle; =20 #ifdef CONFIG_FAIR_GROUP_SCHED - if (!prev || prev->sched_class !=3D &fair_sched_class) + if (!prev || + prev->sched_class !=3D &fair_sched_class || + rq->curr !=3D rq_selected(rq)) goto simple; =20 /* diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 81cd22eaa6dc..a7b51a021111 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1503,6 +1503,9 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p,= int flags) if (p->nr_cpus_allowed =3D=3D 1) return; =20 + if (task_is_blocked(p)) + return; + enqueue_pushable_task(rq, p); } =20 @@ -1790,10 +1793,12 @@ static void put_prev_task_rt(struct rq *rq, struct = task_struct *p) =20 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1); 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Tue, 19 Dec 2023 16:19:29 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:26 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-16-jstultz@google.com> Subject: [PATCH v7 15/23] sched: Add blocked_donor link to task for smarter mutex handoffs From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Add link to the task this task is proxying for, and use it so we do intelligent hand-off of the owned mutex to the task we're running on behalf. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien [jstultz: This patch was split out from larger proxy patch] Signed-off-by: John Stultz --- v5: * Split out from larger proxy patch v6: * Moved proxied value from earlier patch to this one where it is actually used * Rework logic to check sched_proxy_exec() instead of using ifdefs * Moved comment change to this patch where it makes sense v7: * Use more descriptive term then "us" in comments, as suggested by Metin Kaya. * Minor typo fixup from Metin Kaya * Reworked proxied variable to prev_not_proxied to simplify usage --- include/linux/sched.h | 1 + kernel/fork.c | 1 + kernel/locking/mutex.c | 35 ++++++++++++++++++++++++++++++++--- kernel/sched/core.c | 19 +++++++++++++++++-- 4 files changed, 51 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 880af1c3097d..8020e224e057 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1157,6 +1157,7 @@ struct task_struct { =20 enum blocked_on_state blocked_on_state; struct mutex *blocked_on; /* lock we're blocked on */ + struct task_struct *blocked_donor; /* task that is boosting this task */ raw_spinlock_t blocked_lock; =20 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP diff --git a/kernel/fork.c b/kernel/fork.c index b3ba3d22d8b2..138fc23cad43 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2459,6 +2459,7 @@ __latent_entropy struct task_struct *copy_process( =20 p->blocked_on_state =3D BO_RUNNABLE; p->blocked_on =3D NULL; /* not blocked yet */ + p->blocked_donor =3D NULL; /* nobody is boosting p yet */ #ifdef CONFIG_BCACHE p->sequential_io =3D 0; p->sequential_io_avg =3D 0; diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 11dc5cb7a5a3..2711af8c0052 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -910,7 +910,7 @@ EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible); */ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, u= nsigned long ip) { - struct task_struct *next =3D NULL; + struct task_struct *donor, *next =3D NULL; DEFINE_WAKE_Q(wake_q); unsigned long owner; unsigned long flags; @@ -948,7 +948,34 @@ static noinline void __sched __mutex_unlock_slowpath(s= truct mutex *lock, unsigne preempt_disable(); raw_spin_lock_irqsave(&lock->wait_lock, flags); debug_mutex_unlock(lock); - if (!list_empty(&lock->wait_list)) { + + if (sched_proxy_exec()) { + raw_spin_lock(¤t->blocked_lock); + /* + * If we have a task boosting current, and that task was boosting + * current through this lock, hand the lock to that task, as that + * is the highest waiter, as selected by the scheduling function. + */ + donor =3D current->blocked_donor; + if (donor) { + struct mutex *next_lock; + + raw_spin_lock_nested(&donor->blocked_lock, SINGLE_DEPTH_NESTING); + next_lock =3D get_task_blocked_on(donor); + if (next_lock =3D=3D lock) { + next =3D donor; + donor->blocked_on_state =3D BO_WAKING; + wake_q_add(&wake_q, donor); + current->blocked_donor =3D NULL; + } + raw_spin_unlock(&donor->blocked_lock); + } + } + + /* + * Failing that, pick any on the wait list. + */ + if (!next && !list_empty(&lock->wait_list)) { /* get the first entry from the wait-list: */ struct mutex_waiter *waiter =3D list_first_entry(&lock->wait_list, @@ -956,7 +983,7 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne =20 next =3D waiter->task; =20 - raw_spin_lock(&next->blocked_lock); + raw_spin_lock_nested(&next->blocked_lock, SINGLE_DEPTH_NESTING); debug_mutex_wake_waiter(lock, waiter); WARN_ON(next->blocked_on !=3D lock); next->blocked_on_state =3D BO_WAKING; @@ -967,6 +994,8 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne if (owner & MUTEX_FLAG_HANDOFF) __mutex_handoff(lock, next); =20 + if (sched_proxy_exec()) + raw_spin_unlock(¤t->blocked_lock); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); wake_up_q(&wake_q); preempt_enable(); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 55dc2a3b7e46..e0afa228bc9d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6765,7 +6765,17 @@ proxy_migrate_task(struct rq *rq, struct rq_flags *r= f, * Find who @next (currently blocked on a mutex) can proxy for. * * Follow the blocked-on relation: - * task->blocked_on -> mutex->owner -> task... + * + * ,-> task + * | | blocked-on + * | v + * blocked_donor | mutex + * | | owner + * | v + * `-- task + * + * and set the blocked_donor relation, this latter is used by the mutex + * code to find which (blocked) task to hand-off to. * * Lock order: * @@ -6897,6 +6907,8 @@ find_proxy_task(struct rq *rq, struct task_struct *ne= xt, struct rq_flags *rf) */ raw_spin_unlock(&p->blocked_lock); raw_spin_unlock(&mutex->wait_lock); + + owner->blocked_donor =3D p; } =20 WARN_ON_ONCE(owner && !owner->on_rq); @@ -6979,6 +6991,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) unsigned long prev_state; struct rq_flags rf; struct rq *rq; + bool prev_not_proxied; int cpu; bool preserve_need_resched =3D false; =20 @@ -7030,9 +7043,11 @@ static void __sched notrace __schedule(unsigned int = sched_mode) switch_count =3D &prev->nvcsw; } =20 + prev_not_proxied =3D !prev->blocked_donor; pick_again: next =3D pick_next_task(rq, rq_selected(rq), &rf); rq_set_selected(rq, next); + next->blocked_donor =3D NULL; if (unlikely(task_is_blocked(next))) { next =3D find_proxy_task(rq, next, &rf); if (!next) { @@ -7088,7 +7103,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) rq =3D context_switch(rq, prev, next, &rf); } else { /* In case next was already curr but just got blocked_donor*/ - if (!task_current_selected(rq, next)) + if (prev_not_proxied && next->blocked_donor) proxy_tag_curr(rq, next); =20 rq_unpin_lock(rq, &rf); --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 523A81F16B for ; Wed, 20 Dec 2023 00:19:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="YxnHhl0e" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-28b8f963816so2527005a91.1 for ; Tue, 19 Dec 2023 16:19:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031570; x=1703636370; darn=vger.kernel.org; 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Tue, 19 Dec 2023 16:19:30 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:27 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-17-jstultz@google.com> Subject: [PATCH v7 16/23] sched: Add deactivated (sleeping) owner handling to find_proxy_task() From: John Stultz To: LKML Cc: Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra If the blocked_on chain resolves to a sleeping owner, deactivate selected task, and enqueue it on the sleeping owner task. Then re-activate it later when the owner is woken up. NOTE: This has been particularly challenging to get working properly, and some of the locking is particularly ackward. I'd very much appreciate review and feedback for ways to simplify this. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien [jstultz: This was broken out from the larger proxy() patch] Signed-off-by: John Stultz --- v5: * Split out from larger proxy patch v6: * Major rework, replacing the single list head per task with per-task list head and nodes, creating a tree structure so we only wake up decendents of the task woken. * Reworked the locking to take the task->pi_lock, so we can avoid mid-chain wakeup races from try_to_wake_up() called by the ww_mutex logic. v7: * Drop ununessary __nested lock annotation, as we already drop the lock prior. * Add comments on #else & #endif lines, and clearer function names, and commit message tweaks as suggested by Metin Kaya * Move activate_blocked_entities() call from ttwu_queue to try_to_wake_up() to simplify locking. Thanks to questions from Metin Kaya * Fix irqsave/irqrestore usage now we call this outside where the pi_lock is held * Fix activate_blocked_entitites not preserving wake_cpu * Fix for UP builds --- include/linux/sched.h | 3 + kernel/fork.c | 4 + kernel/sched/core.c | 214 ++++++++++++++++++++++++++++++++++++++---- 3 files changed, 202 insertions(+), 19 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 8020e224e057..6f982948a105 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1158,6 +1158,9 @@ struct task_struct { enum blocked_on_state blocked_on_state; struct mutex *blocked_on; /* lock we're blocked on */ struct task_struct *blocked_donor; /* task that is boosting this task */ + struct list_head blocked_head; /* tasks blocked on this task */ + struct list_head blocked_node; /* our entry on someone elses blocked_he= ad */ + struct task_struct *sleeping_owner; /* task our blocked_node is enqueued= on */ raw_spinlock_t blocked_lock; =20 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP diff --git a/kernel/fork.c b/kernel/fork.c index 138fc23cad43..56f5e19c268e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2460,6 +2460,10 @@ __latent_entropy struct task_struct *copy_process( p->blocked_on_state =3D BO_RUNNABLE; p->blocked_on =3D NULL; /* not blocked yet */ p->blocked_donor =3D NULL; /* nobody is boosting p yet */ + + INIT_LIST_HEAD(&p->blocked_head); + INIT_LIST_HEAD(&p->blocked_node); + p->sleeping_owner =3D NULL; #ifdef CONFIG_BCACHE p->sequential_io =3D 0; p->sequential_io_avg =3D 0; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e0afa228bc9d..0cd63bd0bdcd 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3785,6 +3785,133 @@ static inline void ttwu_do_wakeup(struct task_struc= t *p) trace_sched_wakeup(p); } =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +static void do_activate_task(struct rq *rq, struct task_struct *p, int en_= flags) +{ + lockdep_assert_rq_held(rq); + + if (!sched_proxy_exec()) { + activate_task(rq, p, en_flags); + return; + } + + if (p->sleeping_owner) { + struct task_struct *owner =3D p->sleeping_owner; + + raw_spin_lock(&owner->blocked_lock); + list_del_init(&p->blocked_node); + p->sleeping_owner =3D NULL; + raw_spin_unlock(&owner->blocked_lock); + } + + /* + * By calling activate_task with blocked_lock held, we + * order against the find_proxy_task() blocked_task case + * such that no more blocked tasks will be enqueued on p + * once we release p->blocked_lock. + */ + raw_spin_lock(&p->blocked_lock); + WARN_ON(task_cpu(p) !=3D cpu_of(rq)); + activate_task(rq, p, en_flags); + raw_spin_unlock(&p->blocked_lock); +} + +#ifdef CONFIG_SMP +static inline void proxy_set_task_cpu(struct task_struct *p, int cpu) +{ + unsigned int wake_cpu; + + /* Preserve wake_cpu */ + wake_cpu =3D p->wake_cpu; + __set_task_cpu(p, cpu); + p->wake_cpu =3D wake_cpu; +} +#else /* !CONFIG_SMP */ +static inline void proxy_set_task_cpu(struct task_struct *p, int cpu) +{ + __set_task_cpu(p, cpu); +} +#endif /* CONFIG_SMP */ + +static void activate_blocked_entities(struct rq *target_rq, + struct task_struct *owner, + int wake_flags) +{ + unsigned long flags; + struct rq_flags rf; + int target_cpu =3D cpu_of(target_rq); + int en_flags =3D ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; + + if (wake_flags & WF_MIGRATED) + en_flags |=3D ENQUEUE_MIGRATED; + /* + * A whole bunch of 'proxy' tasks back this blocked task, wake + * them all up to give this task its 'fair' share. + */ + raw_spin_lock_irqsave(&owner->blocked_lock, flags); + while (!list_empty(&owner->blocked_head)) { + struct task_struct *pp; + unsigned int state; + + pp =3D list_first_entry(&owner->blocked_head, + struct task_struct, + blocked_node); + BUG_ON(pp =3D=3D owner); + list_del_init(&pp->blocked_node); + WARN_ON(!pp->sleeping_owner); + pp->sleeping_owner =3D NULL; + raw_spin_unlock_irqrestore(&owner->blocked_lock, flags); + + raw_spin_lock_irqsave(&pp->pi_lock, flags); + state =3D READ_ONCE(pp->__state); + /* Avoid racing with ttwu */ + if (state =3D=3D TASK_WAKING) { + raw_spin_unlock_irqrestore(&pp->pi_lock, flags); + raw_spin_lock_irqsave(&owner->blocked_lock, flags); + continue; + } + if (READ_ONCE(pp->on_rq)) { + /* + * We raced with a non mutex handoff activation of pp. + * That activation will also take care of activating + * all of the tasks after pp in the blocked_entry list, + * so we're done here. + */ + raw_spin_unlock_irqrestore(&pp->pi_lock, flags); + raw_spin_lock_irqsave(&owner->blocked_lock, flags); + continue; + } + + proxy_set_task_cpu(pp, target_cpu); + + rq_lock_irqsave(target_rq, &rf); + update_rq_clock(target_rq); + do_activate_task(target_rq, pp, en_flags); + resched_curr(target_rq); + rq_unlock_irqrestore(target_rq, &rf); + raw_spin_unlock_irqrestore(&pp->pi_lock, flags); + + /* recurse - XXX This needs to be reworked to avoid recursing */ + activate_blocked_entities(target_rq, pp, wake_flags); + + raw_spin_lock_irqsave(&owner->blocked_lock, flags); + } + raw_spin_unlock_irqrestore(&owner->blocked_lock, flags); +} +#else /* !CONFIG_SCHED_PROXY_EXEC */ +static inline void do_activate_task(struct rq *rq, struct task_struct *p, + int en_flags) +{ + activate_task(rq, p, en_flags); +} + +static inline void activate_blocked_entities(struct rq *target_rq, + struct task_struct *owner, + int wake_flags) +{ +} +#endif /* CONFIG_SCHED_PROXY_EXEC */ + #ifdef CONFIG_SMP static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p) { @@ -3839,7 +3966,7 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p= , int wake_flags, atomic_dec(&task_rq(p)->nr_iowait); } =20 - activate_task(rq, p, en_flags); + do_activate_task(rq, p, en_flags); wakeup_preempt(rq, p, wake_flags); =20 ttwu_do_wakeup(p); @@ -3936,13 +4063,19 @@ void sched_ttwu_pending(void *arg) update_rq_clock(rq); =20 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { + int wake_flags; if (WARN_ON_ONCE(p->on_cpu)) smp_cond_load_acquire(&p->on_cpu, !VAL); =20 if (WARN_ON_ONCE(task_cpu(p) !=3D cpu_of(rq))) set_task_cpu(p, cpu_of(rq)); =20 - ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); + wake_flags =3D p->sched_remote_wakeup ? WF_MIGRATED : 0; + ttwu_do_activate(rq, p, wake_flags, &rf); + rq_unlock(rq, &rf); + activate_blocked_entities(rq, p, wake_flags); + rq_lock(rq, &rf); + update_rq_clock(rq); } =20 /* @@ -4423,6 +4556,7 @@ int try_to_wake_up(struct task_struct *p, unsigned in= t state, int wake_flags) if (p->blocked_on_state =3D=3D BO_WAKING) p->blocked_on_state =3D BO_RUNNABLE; raw_spin_unlock_irqrestore(&p->blocked_lock, flags); + activate_blocked_entities(cpu_rq(cpu), p, wake_flags); out: if (success) ttwu_stat(p, task_cpu(p), wake_flags); @@ -6663,19 +6797,6 @@ proxy_resched_idle(struct rq *rq, struct task_struct= *next) return rq->idle; } =20 -static bool proxy_deactivate(struct rq *rq, struct task_struct *next) -{ - unsigned long state =3D READ_ONCE(next->__state); - - /* Don't deactivate if the state has been changed to TASK_RUNNING */ - if (state =3D=3D TASK_RUNNING) - return false; - if (!try_to_deactivate_task(rq, next, state, true)) - return false; - proxy_resched_idle(rq, next); - return true; -} - #ifdef CONFIG_SMP /* * If the blocked-on relationship crosses CPUs, migrate @p to the @@ -6761,6 +6882,31 @@ proxy_migrate_task(struct rq *rq, struct rq_flags *r= f, } #endif /* CONFIG_SMP */ =20 +static void proxy_enqueue_on_owner(struct rq *rq, struct task_struct *owne= r, + struct task_struct *next) +{ + /* + * ttwu_activate() will pick them up and place them on whatever rq + * @owner will run next. + */ + if (!owner->on_rq) { + BUG_ON(!next->on_rq); + deactivate_task(rq, next, DEQUEUE_SLEEP); + if (task_current_selected(rq, next)) { + put_prev_task(rq, next); + rq_set_selected(rq, rq->idle); + } + /* + * ttwu_do_activate must not have a chance to activate p + * elsewhere before it's fully extricated from its old rq. + */ + WARN_ON(next->sleeping_owner); + next->sleeping_owner =3D owner; + smp_mb(); + list_add(&next->blocked_node, &owner->blocked_head); + } +} + /* * Find who @next (currently blocked on a mutex) can proxy for. * @@ -6866,10 +7012,40 @@ find_proxy_task(struct rq *rq, struct task_struct *= next, struct rq_flags *rf) } =20 if (!owner->on_rq) { - /* XXX Don't handle blocked owners yet */ - if (!proxy_deactivate(rq, next)) - ret =3D next; - goto out; + /* + * rq->curr must not be added to the blocked_head list or else + * ttwu_do_activate could enqueue it elsewhere before it switches + * out here. The approach to avoid this is the same as in the + * migrate_task case. + */ + if (curr_in_chain) { + raw_spin_unlock(&p->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + return proxy_resched_idle(rq, next); + } + + /* + * If !@owner->on_rq, holding @rq->lock will not pin the task, + * so we cannot drop @mutex->wait_lock until we're sure its a blocked + * task on this rq. + * + * We use @owner->blocked_lock to serialize against ttwu_activate(). + * Either we see its new owner->on_rq or it will see our list_add(). + */ + if (owner !=3D p) { + raw_spin_unlock(&p->blocked_lock); + raw_spin_lock(&owner->blocked_lock); + } + + proxy_enqueue_on_owner(rq, owner, next); + + if (task_current_selected(rq, next)) { + put_prev_task(rq, next); + rq_set_selected(rq, rq->idle); + } + raw_spin_unlock(&owner->blocked_lock); + raw_spin_unlock(&mutex->wait_lock); + return NULL; /* retry task selection */ } =20 if (owner =3D=3D p) { --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 95372200D5 for ; Wed, 20 Dec 2023 00:19:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="umVrC99g" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-5e73bd9079eso32578577b3.2 for ; Tue, 19 Dec 2023 16:19:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031572; x=1703636372; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=AIfyyqU8vvkBxzT4xph+dm2KvcH+GhhY/2ZmCVqXntI=; b=umVrC99gRoJhtjuT9Sr4qw/c6e1DLGzxutQKK5qOnxrXllsSXpXpOoA2UTVmAlqguj gyaNfHIrmyHWLONVtHRsNQKDJXulTbLVt7RHDCv3YSY+OgPu+4UeGXXM5alTZtsYp5xC WkuxSh6Vl6D+IkGLzG1m1yTHKs0AoEyQR94zrvJFIShEXdQ08bWpQg/wMQP87Ngru5vt QPJ/dGfucl8QV+1ThB4XHceWwhAUZ+CSHtQpJ7mbGCaw939xvSQ4/n2lWSxxNKzfXKgI ZL6HxUnRDsLOK2H4ur0IuUwjR2YVtL5UXCyOz7k+Vry/ZUzmF0DtZMp+oCtBV2DhMIEx DBDQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031572; x=1703636372; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=AIfyyqU8vvkBxzT4xph+dm2KvcH+GhhY/2ZmCVqXntI=; b=plgU+p4OW9YSJtcZDuFFQzuZJbU/we6lJwaiB9vwQiRoHWlreqsCmAEi/Aa4B57ROC ZNqcBH00rKaPVXKT6BYDjcx5a/yZPe8LoB4Se4gTmm0ns6y19YwKVhFhWlbnLBInGAJq 9MWmStOpAN5oKF67vTmR5hMS7ot0k+ydOw2oGmjqVOFm2onbMonvR2QYlpEW6dHNrW0c hP5UCYhARmKoyQVeodP1CuwGWTchfHx9pffYpwNoBC1aRYJG35tb05sDphUBnqqZSxBu YO/acuXD5ojz9w8XOwcssFzbi7RM8D9INRpY5CDqK4hejCOUVJ+PAEWnIrObzR85P+58 4Fyg== X-Gm-Message-State: AOJu0Yyuw/YWSTKLd9rrxQJUH5+jQdpAVHuVnjaTcLeDpJWDgg1x5nWa uX8aFRF2uPXnF7IGb2nfXrtGV12we56sG/ejQGmFlmcFnhn48/vpcmMAV07ddvSCH5hbAILh95x egTCs1EyzIj7AvNUe0mZog7TrKvsTw/GnDy+SlATtL2RhCRlSaDX/NvsBr0j6mHZ9ptrG9O4= X-Google-Smtp-Source: AGHT+IEQVD9hjXxmvtfUNLzEVhTlYwXthri2unuNndqCOZSGlx11NHsaq76wkJ/AvlLoDcuPbV2MaXu/49yn X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:690c:4491:b0:5e8:3e57:6900 with SMTP id gr17-20020a05690c449100b005e83e576900mr423186ywb.1.1703031572518; Tue, 19 Dec 2023 16:19:32 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:28 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-18-jstultz@google.com> Subject: [PATCH v7 17/23] sched: Initial sched_football test implementation From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Reimplementation of the sched_football test from LTP: https://github.com/linux-test-project/ltp/blob/master/testcases/realtime/fu= nc/sched_football/sched_football.c But reworked to run in the kernel and utilize mutexes to illustrate proper boosting of low priority mutex holders. TODO: * Need a rt_mutex version so it can work w/o proxy-execution * Need a better place to put it Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- kernel/sched/Makefile | 1 + kernel/sched/test_sched_football.c | 242 +++++++++++++++++++++++++++++ lib/Kconfig.debug | 14 ++ 3 files changed, 257 insertions(+) create mode 100644 kernel/sched/test_sched_football.c diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 976092b7bd45..2729d565dfd7 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -32,3 +32,4 @@ obj-y +=3D core.o obj-y +=3D fair.o obj-y +=3D build_policy.o obj-y +=3D build_utility.o +obj-$(CONFIG_SCHED_RT_INVARIENT_TEST) +=3D test_sched_football.o diff --git a/kernel/sched/test_sched_football.c b/kernel/sched/test_sched_f= ootball.c new file mode 100644 index 000000000000..9742c45c0fe0 --- /dev/null +++ b/kernel/sched/test_sched_football.c @@ -0,0 +1,242 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Module-based test case for RT scheduling invariant + * + * A reimplementation of my old sched_football test + * found in LTP: + * https://github.com/linux-test-project/ltp/blob/master/testcases/realt= ime/func/sched_football/sched_football.c + * + * Similar to that test, this tries to validate the RT + * scheduling invariant, that the across N available cpus, the + * top N priority tasks always running. + * + * This is done via having N offsensive players that are + * medium priority, which constantly are trying to increment the + * ball_pos counter. + * + * Blocking this, are N defensive players that are higher + * priority which just spin on the cpu, preventing the medium + * priroity tasks from running. + * + * To complicate this, there are also N defensive low priority + * tasks. These start first and each aquire one of N mutexes. + * The high priority defense tasks will later try to grab the + * mutexes and block, opening a window for the offsensive tasks + * to run and increment the ball. If priority inheritance or + * proxy execution is used, the low priority defense players + * should be boosted to the high priority levels, and will + * prevent the mid priority offensive tasks from running. + * + * Copyright =C2=A9 International Business Machines Corp., 2007, 2008 + * Copyright (C) Google, 2023 + * + * Authors: John Stultz + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +atomic_t players_ready; +atomic_t ball_pos; +int players_per_team; +bool game_over; + +struct mutex *mutex_low_list; +struct mutex *mutex_mid_list; + +static inline +struct task_struct *create_fifo_thread(int (*threadfn)(void *data), void *= data, + char *name, int prio) +{ + struct task_struct *kth; + struct sched_attr attr =3D { + .size =3D sizeof(struct sched_attr), + .sched_policy =3D SCHED_FIFO, + .sched_nice =3D 0, + .sched_priority =3D prio, + }; + int ret; + + kth =3D kthread_create(threadfn, data, name); + if (IS_ERR(kth)) { + pr_warn("%s eerr, kthread_create failed\n", __func__); + return kth; + } + ret =3D sched_setattr_nocheck(kth, &attr); + if (ret) { + kthread_stop(kth); + pr_warn("%s: failed to set SCHED_FIFO\n", __func__); + return ERR_PTR(ret); + } + + wake_up_process(kth); + return kth; +} + +int defense_low_thread(void *arg) +{ + long tnum =3D (long)arg; + + atomic_inc(&players_ready); + mutex_lock(&mutex_low_list[tnum]); + while (!READ_ONCE(game_over)) { + if (kthread_should_stop()) + break; + schedule(); + } + mutex_unlock(&mutex_low_list[tnum]); + return 0; +} + +int defense_mid_thread(void *arg) +{ + long tnum =3D (long)arg; + + atomic_inc(&players_ready); + mutex_lock(&mutex_mid_list[tnum]); + mutex_lock(&mutex_low_list[tnum]); + while (!READ_ONCE(game_over)) { + if (kthread_should_stop()) + break; + schedule(); + } + mutex_unlock(&mutex_low_list[tnum]); + mutex_unlock(&mutex_mid_list[tnum]); + return 0; +} + +int offense_thread(void *) +{ + atomic_inc(&players_ready); + while (!READ_ONCE(game_over)) { + if (kthread_should_stop()) + break; + schedule(); + atomic_inc(&ball_pos); + } + return 0; +} + +int defense_hi_thread(void *arg) +{ + long tnum =3D (long)arg; + + atomic_inc(&players_ready); + mutex_lock(&mutex_mid_list[tnum]); + while (!READ_ONCE(game_over)) { + if (kthread_should_stop()) + break; + schedule(); + } + mutex_unlock(&mutex_mid_list[tnum]); + return 0; +} + +int crazy_fan_thread(void *) +{ + int count =3D 0; + + atomic_inc(&players_ready); + while (!READ_ONCE(game_over)) { + if (kthread_should_stop()) + break; + schedule(); + udelay(1000); + msleep(2); + count++; + } + return 0; +} + +int ref_thread(void *arg) +{ + struct task_struct *kth; + long game_time =3D (long)arg; + unsigned long final_pos; + long i; + + pr_info("%s: started ref, game_time: %ld secs !\n", __func__, + game_time); + + /* Create low priority defensive team */ + for (i =3D 0; i < players_per_team; i++) + kth =3D create_fifo_thread(defense_low_thread, (void *)i, + "defese-low-thread", 2); + /* Wait for the defense threads to start */ + while (atomic_read(&players_ready) < players_per_team) + msleep(1); + + for (i =3D 0; i < players_per_team; i++) + kth =3D create_fifo_thread(defense_mid_thread, + (void *)(players_per_team - i - 1), + "defese-mid-thread", 3); + /* Wait for the defense threads to start */ + while (atomic_read(&players_ready) < players_per_team * 2) + msleep(1); + + /* Create mid priority offensive team */ + for (i =3D 0; i < players_per_team; i++) + kth =3D create_fifo_thread(offense_thread, NULL, + "offense-thread", 5); + /* Wait for the offense threads to start */ + while (atomic_read(&players_ready) < players_per_team * 3) + msleep(1); + + /* Create high priority defensive team */ + for (i =3D 0; i < players_per_team; i++) + kth =3D create_fifo_thread(defense_hi_thread, (void *)i, + "defese-hi-thread", 10); + /* Wait for the defense threads to start */ + while (atomic_read(&players_ready) < players_per_team * 4) + msleep(1); + + /* Create high priority defensive team */ + for (i =3D 0; i < players_per_team; i++) + kth =3D create_fifo_thread(crazy_fan_thread, NULL, + "crazy-fan-thread", 15); + /* Wait for the defense threads to start */ + while (atomic_read(&players_ready) < players_per_team * 5) + msleep(1); + + pr_info("%s: all players checked in! Starting game.\n", __func__); + atomic_set(&ball_pos, 0); + msleep(game_time * 1000); + final_pos =3D atomic_read(&ball_pos); + pr_info("%s: final ball_pos: %ld\n", __func__, final_pos); + WARN_ON(final_pos !=3D 0); + game_over =3D true; + return 0; +} + +static int __init test_sched_football_init(void) +{ + struct task_struct *kth; + int i; + + players_per_team =3D num_online_cpus(); + + mutex_low_list =3D kmalloc_array(players_per_team, sizeof(struct mutex),= GFP_ATOMIC); + mutex_mid_list =3D kmalloc_array(players_per_team, sizeof(struct mutex),= GFP_ATOMIC); + + for (i =3D 0; i < players_per_team; i++) { + mutex_init(&mutex_low_list[i]); + mutex_init(&mutex_mid_list[i]); + } + + kth =3D create_fifo_thread(ref_thread, (void *)10, "ref-thread", 20); + + return 0; +} +module_init(test_sched_football_init); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 4405f81248fb..1d90059d190f 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1238,6 +1238,20 @@ config SCHED_DEBUG that can help debug the scheduler. The runtime overhead of this option is minimal. =20 +config SCHED_RT_INVARIENT_TEST + tristate "RT invarient scheduling tester" + depends on DEBUG_KERNEL + help + This option provides a kernel module that runs tests to make + sure the RT invarient holds (top N priority tasks run on N + available cpus). + + Say Y here if you want kernel rt scheduling tests + to be built into the kernel. + Say M if you want this test to build as a module. + Say N if you are unsure. + + config SCHED_INFO bool default n --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B50A8208DA for ; Wed, 20 Dec 2023 00:19:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="L7YCRIpB" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5e617562a65so44910647b3.1 for ; Tue, 19 Dec 2023 16:19:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031574; x=1703636374; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=NGhThAZPlKuA3DG9SjSGW+fpPhrooALxVkfxxcKParw=; b=L7YCRIpB6vKiiJgC63DQSXvgdbkErP0jGYoJAjBj/lr5eBFz68Hko82Z37XnqWEW2v 7olIuzPZQQjfQcL2TKFxLubLWQRUyQ0CYsPN4AcGuhq+VJo8E3nZeI5csinnaJ7conEU CptNzn6/zW0FBak0vq35O1oU5c4BnVRFZ0YUkISJVW4griuqvNxtzRN+8y7ArI2dOMVW +lQDtXfpyHEQNgbtPoIowsIBEq920WPJHwW0XtNsuMFbrVs8hQnJQt14enJTKLqe+VZr Q3rduyTQ22yyRhntoFlrt71CyLeXSuneoP1FaxGAxbr3ACkiEtL2uQU8xCOe5OtaVaCQ zuSA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031574; x=1703636374; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NGhThAZPlKuA3DG9SjSGW+fpPhrooALxVkfxxcKParw=; b=vpE5r7p25mFmenXTHzRu3l9Lk7zv9305zYHgcNVWZ50YYxo54o9Qidyo6sd3CKwPVW /sfCStSN741RU48K20qt9g2GN32kRi5092RNkO/LZ40GjEAO+ClMfuQ7+imEHqJn0cA1 v0EaN74GJNyu1w/a2Zh+h8OZO8b0I4nX/rpbyNCV9+nsfonDwaYMT8dlrBYl9hDzyAkK N/Lpg9qgkp2QPS58jrZesSVJncPt4RiIHCJ6vvKwHIMyvKGfTFidtR9TvKBb+NllWmdH UEVoiI2fuf3CZd1eE3tmMIIw12qCsNkX2wTVM3DvNoVlqIub/GXOg83wMA/ygWJ6LLWT dZ3w== X-Gm-Message-State: AOJu0YyuspeXdTYAGjmuzhUYeixAQERcah91gp19dnxx9nTLYPbT2Pq5 Cs0fM70eSPGAWls3lvKsA1Cv7ZAkUkW0FPsy5L5Dg7K+cQ5KGugdMoiTGBH60gibbCwdYtDBV7e ZQzsUxphmPcBznI3XHZrcORzG1N3cTINLhudN+SHRWdrdyS1xZQjpYKA/zuFoxoI1wnqEgNU= X-Google-Smtp-Source: AGHT+IHyKlq58eERpBcLB7I11Bb4HermitDwI1gx5J6zFvTyMlHHWSwbUdgG2IY5MsXykKlPExet0+cL7E19 X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:690c:d93:b0:5d4:3013:25d4 with SMTP id da19-20020a05690c0d9300b005d4301325d4mr3569079ywb.5.1703031574440; Tue, 19 Dec 2023 16:19:34 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:29 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-19-jstultz@google.com> Subject: [PATCH v7 18/23] sched: Add push_task_chain helper From: John Stultz To: LKML Cc: "Connor O'Brien" , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Connor O'Brien Switch logic that deactivates, sets the task cpu, and reactivates a task on a different rq to use a helper that will be later extended to push entire blocked task chains. This patch was broken out from a larger chain migration patch originally by Connor O'Brien. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Connor O'Brien [jstultz: split out from larger chain migration patch] Signed-off-by: John Stultz --- kernel/sched/core.c | 4 +--- kernel/sched/deadline.c | 8 ++------ kernel/sched/rt.c | 8 ++------ kernel/sched/sched.h | 9 +++++++++ 4 files changed, 14 insertions(+), 15 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0cd63bd0bdcd..0c212dcd4b7a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2721,9 +2721,7 @@ int push_cpu_stop(void *arg) =20 // XXX validate p is still the highest prio task if (task_rq(p) =3D=3D rq) { - deactivate_task(rq, p, 0); - set_task_cpu(p, lowest_rq->cpu); - activate_task(lowest_rq, p, 0); + push_task_chain(rq, lowest_rq, p); resched_curr(lowest_rq); } =20 diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 4f998549ea74..def1eb23318b 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2313,9 +2313,7 @@ static int push_dl_task(struct rq *rq) goto retry; } =20 - deactivate_task(rq, next_task, 0); - set_task_cpu(next_task, later_rq->cpu); - activate_task(later_rq, next_task, 0); + push_task_chain(rq, later_rq, next_task); ret =3D 1; =20 resched_curr(later_rq); @@ -2401,9 +2399,7 @@ static void pull_dl_task(struct rq *this_rq) if (is_migration_disabled(p)) { push_task =3D get_push_task(src_rq); } else { - deactivate_task(src_rq, p, 0); - set_task_cpu(p, this_cpu); - activate_task(this_rq, p, 0); + push_task_chain(src_rq, this_rq, p); dmin =3D p->dl.deadline; resched =3D true; } diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index a7b51a021111..cf0eb4aac613 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2128,9 +2128,7 @@ static int push_rt_task(struct rq *rq, bool pull) goto retry; } =20 - deactivate_task(rq, next_task, 0); - set_task_cpu(next_task, lowest_rq->cpu); - activate_task(lowest_rq, next_task, 0); + push_task_chain(rq, lowest_rq, next_task); resched_curr(lowest_rq); ret =3D 1; =20 @@ -2401,9 +2399,7 @@ static void pull_rt_task(struct rq *this_rq) if (is_migration_disabled(p)) { push_task =3D get_push_task(src_rq); } else { - deactivate_task(src_rq, p, 0); - set_task_cpu(p, this_cpu); - activate_task(this_rq, p, 0); + push_task_chain(src_rq, this_rq, p); resched =3D true; } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 765ba10661de..19afe532771f 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3546,5 +3546,14 @@ static inline void init_sched_mm_cid(struct task_str= uct *t) { } =20 extern u64 avg_vruntime(struct cfs_rq *cfs_rq); extern int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se); +#ifdef CONFIG_SMP +static inline +void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task) +{ + deactivate_task(rq, task, 0); + set_task_cpu(task, dst_rq->cpu); + activate_task(dst_rq, task, 0); +} +#endif =20 #endif /* _KERNEL_SCHED_SCHED_H */ --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6751420B31 for ; 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Tue, 19 Dec 2023 16:19:36 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:30 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-20-jstultz@google.com> Subject: [PATCH v7 19/23] sched: Consolidate pick_*_task to task_is_pushable helper From: John Stultz To: LKML Cc: "Connor O'Brien" , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Connor O'Brien This patch consolidates rt and deadline pick_*_task functions to a task_is_pushable() helper This patch was broken out from a larger chain migration patch originally by Connor O'Brien. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Connor O'Brien [jstultz: split out from larger chain migration patch, renamed helper function] Signed-off-by: John Stultz --- v7: * Split from chain migration patch * Renamed function --- kernel/sched/deadline.c | 10 +--------- kernel/sched/rt.c | 11 +---------- kernel/sched/sched.h | 10 ++++++++++ 3 files changed, 12 insertions(+), 19 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index def1eb23318b..1f3bc50de678 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2049,14 +2049,6 @@ static void task_fork_dl(struct task_struct *p) /* Only try algorithms three times */ #define DL_MAX_TRIES 3 =20 -static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu) -{ - if (!task_on_cpu(rq, p) && - cpumask_test_cpu(cpu, &p->cpus_mask)) - return 1; - return 0; -} - /* * Return the earliest pushable rq's task, which is suitable to be executed * on the CPU, NULL otherwise: @@ -2075,7 +2067,7 @@ static struct task_struct *pick_earliest_pushable_dl_= task(struct rq *rq, int cpu if (next_node) { p =3D __node_2_pdl(next_node); =20 - if (pick_dl_task(rq, p, cpu)) + if (task_is_pushable(rq, p, cpu) =3D=3D 1) return p; =20 next_node =3D rb_next(next_node); diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index cf0eb4aac613..15161de88753 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1812,15 +1812,6 @@ static void put_prev_task_rt(struct rq *rq, struct t= ask_struct *p) /* Only try algorithms three times */ #define RT_MAX_TRIES 3 =20 -static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) -{ - if (!task_on_cpu(rq, p) && - cpumask_test_cpu(cpu, &p->cpus_mask)) - return 1; - - return 0; -} - /* * Return the highest pushable rq's task, which is suitable to be executed * on the CPU, NULL otherwise @@ -1834,7 +1825,7 @@ static struct task_struct *pick_highest_pushable_task= (struct rq *rq, int cpu) return NULL; =20 plist_for_each_entry(p, head, pushable_tasks) { - if (pick_rt_task(rq, p, cpu)) + if (task_is_pushable(rq, p, cpu) =3D=3D 1) return p; } =20 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 19afe532771f..ef3d327e267c 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3554,6 +3554,16 @@ void push_task_chain(struct rq *rq, struct rq *dst_r= q, struct task_struct *task) set_task_cpu(task, dst_rq->cpu); activate_task(dst_rq, task, 0); } + +static inline +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu) +{ + if (!task_on_cpu(rq, p) && + cpumask_test_cpu(cpu, &p->cpus_mask)) + return 1; + + return 0; +} #endif =20 #endif /* _KERNEL_SCHED_SCHED_H */ --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 264C521102 for ; Wed, 20 Dec 2023 00:19:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nV01vLsQ" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dbd5905aa71so905616276.2 for ; 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Tue, 19 Dec 2023 16:19:38 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:31 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-21-jstultz@google.com> Subject: [PATCH v7 20/23] sched: Push execution and scheduler context split into deadline and rt paths From: John Stultz To: LKML Cc: "Connor O'Brien" , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Connor O'Brien In preparation for chain migration, push the awareness of the split between execution and scheduler context down into some of the rt/deadline code paths that deal with load balancing. This patch was broken out from a larger chain migration patch originally by Connor O'Brien. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Connor O'Brien [jstultz: split out from larger chain migration patch] Signed-off-by: John Stultz --- kernel/sched/cpudeadline.c | 12 ++++++------ kernel/sched/cpudeadline.h | 3 ++- kernel/sched/cpupri.c | 20 +++++++++++--------- kernel/sched/cpupri.h | 6 ++++-- kernel/sched/deadline.c | 18 +++++++++--------- kernel/sched/rt.c | 31 ++++++++++++++++++------------- 6 files changed, 50 insertions(+), 40 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 95baa12a1029..6ac59dcdf068 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -113,13 +113,13 @@ static inline int cpudl_maximum(struct cpudl *cp) * * Returns: int - CPUs were found */ -int cpudl_find(struct cpudl *cp, struct task_struct *p, +int cpudl_find(struct cpudl *cp, struct task_struct *sched_ctx, struct tas= k_struct *exec_ctx, struct cpumask *later_mask) { - const struct sched_dl_entity *dl_se =3D &p->dl; + const struct sched_dl_entity *dl_se =3D &sched_ctx->dl; =20 if (later_mask && - cpumask_and(later_mask, cp->free_cpus, &p->cpus_mask)) { + cpumask_and(later_mask, cp->free_cpus, &exec_ctx->cpus_mask)) { unsigned long cap, max_cap =3D 0; int cpu, max_cpu =3D -1; =20 @@ -128,13 +128,13 @@ int cpudl_find(struct cpudl *cp, struct task_struct *= p, =20 /* Ensure the capacity of the CPUs fits the task. */ for_each_cpu(cpu, later_mask) { - if (!dl_task_fits_capacity(p, cpu)) { + if (!dl_task_fits_capacity(sched_ctx, cpu)) { cpumask_clear_cpu(cpu, later_mask); =20 cap =3D arch_scale_cpu_capacity(cpu); =20 if (cap > max_cap || - (cpu =3D=3D task_cpu(p) && cap =3D=3D max_cap)) { + (cpu =3D=3D task_cpu(exec_ctx) && cap =3D=3D max_cap)) { max_cap =3D cap; max_cpu =3D cpu; } @@ -150,7 +150,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, =20 WARN_ON(best_cpu !=3D -1 && !cpu_present(best_cpu)); =20 - if (cpumask_test_cpu(best_cpu, &p->cpus_mask) && + if (cpumask_test_cpu(best_cpu, &exec_ctx->cpus_mask) && dl_time_before(dl_se->deadline, cp->elements[0].dl)) { if (later_mask) cpumask_set_cpu(best_cpu, later_mask); diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h index 0adeda93b5fb..6bb27f70e9d2 100644 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -16,7 +16,8 @@ struct cpudl { }; =20 #ifdef CONFIG_SMP -int cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *l= ater_mask); +int cpudl_find(struct cpudl *cp, struct task_struct *sched_ctx, + struct task_struct *exec_ctx, struct cpumask *later_mask); void cpudl_set(struct cpudl *cp, int cpu, u64 dl); void cpudl_clear(struct cpudl *cp, int cpu); int cpudl_init(struct cpudl *cp); diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c index 42c40cfdf836..15e947a3ded7 100644 --- a/kernel/sched/cpupri.c +++ b/kernel/sched/cpupri.c @@ -118,10 +118,11 @@ static inline int __cpupri_find(struct cpupri *cp, st= ruct task_struct *p, return 1; } =20 -int cpupri_find(struct cpupri *cp, struct task_struct *p, +int cpupri_find(struct cpupri *cp, struct task_struct *sched_ctx, + struct task_struct *exec_ctx, struct cpumask *lowest_mask) { - return cpupri_find_fitness(cp, p, lowest_mask, NULL); + return cpupri_find_fitness(cp, sched_ctx, exec_ctx, lowest_mask, NULL); } =20 /** @@ -141,18 +142,19 @@ int cpupri_find(struct cpupri *cp, struct task_struct= *p, * * Return: (int)bool - CPUs were found */ -int cpupri_find_fitness(struct cpupri *cp, struct task_struct *p, - struct cpumask *lowest_mask, - bool (*fitness_fn)(struct task_struct *p, int cpu)) +int cpupri_find_fitness(struct cpupri *cp, struct task_struct *sched_ctx, + struct task_struct *exec_ctx, + struct cpumask *lowest_mask, + bool (*fitness_fn)(struct task_struct *p, int cpu)) { - int task_pri =3D convert_prio(p->prio); + int task_pri =3D convert_prio(sched_ctx->prio); int idx, cpu; =20 WARN_ON_ONCE(task_pri >=3D CPUPRI_NR_PRIORITIES); =20 for (idx =3D 0; idx < task_pri; idx++) { =20 - if (!__cpupri_find(cp, p, lowest_mask, idx)) + if (!__cpupri_find(cp, exec_ctx, lowest_mask, idx)) continue; =20 if (!lowest_mask || !fitness_fn) @@ -160,7 +162,7 @@ int cpupri_find_fitness(struct cpupri *cp, struct task_= struct *p, =20 /* Ensure the capacity of the CPUs fit the task */ for_each_cpu(cpu, lowest_mask) { - if (!fitness_fn(p, cpu)) + if (!fitness_fn(sched_ctx, cpu)) cpumask_clear_cpu(cpu, lowest_mask); } =20 @@ -192,7 +194,7 @@ int cpupri_find_fitness(struct cpupri *cp, struct task_= struct *p, * really care. */ if (fitness_fn) - return cpupri_find(cp, p, lowest_mask); + return cpupri_find(cp, sched_ctx, exec_ctx, lowest_mask); =20 return 0; } diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h index d6cba0020064..bde7243cec2e 100644 --- a/kernel/sched/cpupri.h +++ b/kernel/sched/cpupri.h @@ -18,9 +18,11 @@ struct cpupri { }; =20 #ifdef CONFIG_SMP -int cpupri_find(struct cpupri *cp, struct task_struct *p, +int cpupri_find(struct cpupri *cp, struct task_struct *sched_ctx, + struct task_struct *exec_ctx, struct cpumask *lowest_mask); -int cpupri_find_fitness(struct cpupri *cp, struct task_struct *p, +int cpupri_find_fitness(struct cpupri *cp, struct task_struct *sched_ctx, + struct task_struct *exec_ctx, struct cpumask *lowest_mask, bool (*fitness_fn)(struct task_struct *p, int cpu)); void cpupri_set(struct cpupri *cp, int cpu, int pri); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 1f3bc50de678..999bd17f11c4 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1779,7 +1779,7 @@ static inline bool dl_task_is_earliest_deadline(struc= t task_struct *p, rq->dl.earliest_dl.curr)); } =20 -static int find_later_rq(struct task_struct *task); +static int find_later_rq(struct task_struct *sched_ctx, struct task_struct= *exec_ctx); =20 static int select_task_rq_dl(struct task_struct *p, int cpu, int flags) @@ -1819,7 +1819,7 @@ select_task_rq_dl(struct task_struct *p, int cpu, int= flags) select_rq |=3D !dl_task_fits_capacity(p, cpu); =20 if (select_rq) { - int target =3D find_later_rq(p); + int target =3D find_later_rq(p, p); =20 if (target !=3D -1 && dl_task_is_earliest_deadline(p, cpu_rq(target))) @@ -1871,7 +1871,7 @@ static void check_preempt_equal_dl(struct rq *rq, str= uct task_struct *p) * let's hope p can move out. */ if (rq->curr->nr_cpus_allowed =3D=3D 1 || - !cpudl_find(&rq->rd->cpudl, rq_selected(rq), NULL)) + !cpudl_find(&rq->rd->cpudl, rq_selected(rq), rq->curr, NULL)) return; =20 /* @@ -1879,7 +1879,7 @@ static void check_preempt_equal_dl(struct rq *rq, str= uct task_struct *p) * see if it is pushed or pulled somewhere else. */ if (p->nr_cpus_allowed !=3D 1 && - cpudl_find(&rq->rd->cpudl, p, NULL)) + cpudl_find(&rq->rd->cpudl, p, p, NULL)) return; =20 resched_curr(rq); @@ -2079,25 +2079,25 @@ static struct task_struct *pick_earliest_pushable_d= l_task(struct rq *rq, int cpu =20 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl); =20 -static int find_later_rq(struct task_struct *task) +static int find_later_rq(struct task_struct *sched_ctx, struct task_struct= *exec_ctx) { struct sched_domain *sd; struct cpumask *later_mask =3D this_cpu_cpumask_var_ptr(local_cpu_mask_dl= ); int this_cpu =3D smp_processor_id(); - int cpu =3D task_cpu(task); + int cpu =3D task_cpu(sched_ctx); =20 /* Make sure the mask is initialized first */ if (unlikely(!later_mask)) return -1; =20 - if (task->nr_cpus_allowed =3D=3D 1) + if (exec_ctx && exec_ctx->nr_cpus_allowed =3D=3D 1) return -1; =20 /* * We have to consider system topology and task affinity * first, then we can look for a suitable CPU. */ - if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask)) + if (!cpudl_find(&task_rq(exec_ctx)->rd->cpudl, sched_ctx, exec_ctx, later= _mask)) return -1; =20 /* @@ -2174,7 +2174,7 @@ static struct rq *find_lock_later_rq(struct task_stru= ct *task, struct rq *rq) int cpu; =20 for (tries =3D 0; tries < DL_MAX_TRIES; tries++) { - cpu =3D find_later_rq(task); + cpu =3D find_later_rq(task, task); =20 if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu)) break; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 15161de88753..6371b0fca4ad 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1554,7 +1554,7 @@ static void yield_task_rt(struct rq *rq) } =20 #ifdef CONFIG_SMP -static int find_lowest_rq(struct task_struct *task); +static int find_lowest_rq(struct task_struct *sched_ctx, struct task_struc= t *exec_ctx); =20 static int select_task_rq_rt(struct task_struct *p, int cpu, int flags) @@ -1604,7 +1604,7 @@ select_task_rq_rt(struct task_struct *p, int cpu, int= flags) (curr->nr_cpus_allowed < 2 || selected->prio <=3D p->prio); =20 if (test || !rt_task_fits_capacity(p, cpu)) { - int target =3D find_lowest_rq(p); + int target =3D find_lowest_rq(p, p); =20 /* * Bail out if we were forcing a migration to find a better @@ -1631,8 +1631,13 @@ select_task_rq_rt(struct task_struct *p, int cpu, in= t flags) =20 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p) { + struct task_struct *exec_ctx =3D p; + /* + * Current can't be migrated, useless to reschedule, + * let's hope p can move out. + */ if (rq->curr->nr_cpus_allowed =3D=3D 1 || - !cpupri_find(&rq->rd->cpupri, rq_selected(rq), NULL)) + !cpupri_find(&rq->rd->cpupri, rq_selected(rq), rq->curr, NULL)) return; =20 /* @@ -1640,7 +1645,7 @@ static void check_preempt_equal_prio(struct rq *rq, s= truct task_struct *p) * see if it is pushed or pulled somewhere else. */ if (p->nr_cpus_allowed !=3D 1 && - cpupri_find(&rq->rd->cpupri, p, NULL)) + cpupri_find(&rq->rd->cpupri, p, exec_ctx, NULL)) return; =20 /* @@ -1834,19 +1839,19 @@ static struct task_struct *pick_highest_pushable_ta= sk(struct rq *rq, int cpu) =20 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask); =20 -static int find_lowest_rq(struct task_struct *task) +static int find_lowest_rq(struct task_struct *sched_ctx, struct task_struc= t *exec_ctx) { struct sched_domain *sd; struct cpumask *lowest_mask =3D this_cpu_cpumask_var_ptr(local_cpu_mask); int this_cpu =3D smp_processor_id(); - int cpu =3D task_cpu(task); + int cpu =3D task_cpu(sched_ctx); int ret; =20 /* Make sure the mask is initialized first */ if (unlikely(!lowest_mask)) return -1; =20 - if (task->nr_cpus_allowed =3D=3D 1) + if (exec_ctx && exec_ctx->nr_cpus_allowed =3D=3D 1) return -1; /* No other targets possible */ =20 /* @@ -1855,13 +1860,13 @@ static int find_lowest_rq(struct task_struct *task) */ if (sched_asym_cpucap_active()) { =20 - ret =3D cpupri_find_fitness(&task_rq(task)->rd->cpupri, - task, lowest_mask, + ret =3D cpupri_find_fitness(&task_rq(sched_ctx)->rd->cpupri, + sched_ctx, exec_ctx, lowest_mask, rt_task_fits_capacity); } else { =20 - ret =3D cpupri_find(&task_rq(task)->rd->cpupri, - task, lowest_mask); + ret =3D cpupri_find(&task_rq(sched_ctx)->rd->cpupri, + sched_ctx, exec_ctx, lowest_mask); } =20 if (!ret) @@ -1933,7 +1938,7 @@ static struct rq *find_lock_lowest_rq(struct task_str= uct *task, struct rq *rq) int cpu; =20 for (tries =3D 0; tries < RT_MAX_TRIES; tries++) { - cpu =3D find_lowest_rq(task); + cpu =3D find_lowest_rq(task, task); =20 if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu)) break; @@ -2055,7 +2060,7 @@ static int push_rt_task(struct rq *rq, bool pull) if (rq->curr->sched_class !=3D &rt_sched_class) return 0; =20 - cpu =3D find_lowest_rq(rq->curr); + cpu =3D find_lowest_rq(rq_selected(rq), rq->curr); if (cpu =3D=3D -1 || cpu =3D=3D rq->cpu) return 0; =20 --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5DA582136C for ; Wed, 20 Dec 2023 00:19:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; 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bh=6y8S+nSE7+9Tt9N3qq9zNMzLoztzpop33DDkxCG+ySI=; b=RipDc+lyIB3WzqH5i4ShBzIudn+tBiN5f7gJjIFk1rpZ+6bNdJ5qjHkJ/BkPPVp9nd Ot1vMnic6JGqXExnFKKr/yZ6TpqmYEf1grs7sELcea4dvjdqw7+hwxJCsFQ++6+myJfY GkVZMAaQgdwF20086x3nvuDe5rcJ5Hp85F1ffIUvUdVrt2vYObq19F1MfvmDHt9pqn09 ZNzucZhW2l/gX1khylNORi62998tyvjdVQsyuErgf+2S7zyHbmIvfDuferPo1B5cTL4E u1ELvhLTSyRT3YVjqzDJe0QvHeNxL/HKQe1AzgTT8HmUP+L+L8UB6sURZjlMd3MvC74u Cs8Q== X-Gm-Message-State: AOJu0YzmGqkhZL2WjSWAJhs90YOmxvPRzz7P3MpSSHG/gQHs8H/o2isl t00XOLVnYwCUq3Ht5RChJS1MLeMx7cdIi0x8poIeJ/A2wiRyQmZEVR23XgM9SHGpHhW51hlLvCa QSpwm+XpHe7GENRss4NQPeDDKAsAFkKS0qeR2EJom1betX1qLAq72p8PteD3aG6PdJt00xPM= X-Google-Smtp-Source: AGHT+IFxYmvsF0VHJev0Gi/Z/vUlwephStqUcSLGlwMkwFIpbu2UuRc6ddNfrjreND8D2nC2xY9cm7pr0X5O X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a63:5c07:0:b0:5ca:4440:234c with SMTP id q7-20020a635c07000000b005ca4440234cmr772730pgb.12.1703031580069; Tue, 19 Dec 2023 16:19:40 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:32 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-22-jstultz@google.com> Subject: [PATCH v7 21/23] sched: Add find_exec_ctx helper From: John Stultz To: LKML Cc: "Connor O'Brien" , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Connor O'Brien Add a helper to find the runnable owner down a chain of blocked waiters This patch was broken out from a larger chain migration patch originally by Connor O'Brien. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Connor O'Brien [jstultz: split out from larger chain migration patch] Signed-off-by: John Stultz --- kernel/sched/core.c | 42 +++++++++++++++++++++++++++++++++++++++++ kernel/sched/cpupri.c | 11 ++++++++--- kernel/sched/deadline.c | 15 +++++++++++++-- kernel/sched/rt.c | 9 ++++++++- kernel/sched/sched.h | 10 ++++++++++ 5 files changed, 81 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0c212dcd4b7a..77a79d5f829a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3896,6 +3896,48 @@ static void activate_blocked_entities(struct rq *tar= get_rq, } raw_spin_unlock_irqrestore(&owner->blocked_lock, flags); } + +static inline bool task_queued_on_rq(struct rq *rq, struct task_struct *ta= sk) +{ + if (!task_on_rq_queued(task)) + return false; + smp_rmb(); + if (task_rq(task) !=3D rq) + return false; + smp_rmb(); + if (!task_on_rq_queued(task)) + return false; + return true; +} + +/* + * Returns the unblocked task at the end of the blocked chain starting wit= h p + * if that chain is composed entirely of tasks enqueued on rq, or NULL oth= erwise. + */ +struct task_struct *find_exec_ctx(struct rq *rq, struct task_struct *p) +{ + struct task_struct *exec_ctx, *owner; + struct mutex *mutex; + + if (!sched_proxy_exec()) + return p; + + lockdep_assert_rq_held(rq); + + for (exec_ctx =3D p; task_is_blocked(exec_ctx) && !task_on_cpu(rq, exec_c= tx); + exec_ctx =3D owner) { + mutex =3D exec_ctx->blocked_on; + owner =3D __mutex_owner(mutex); + if (owner =3D=3D exec_ctx) + break; + + if (!task_queued_on_rq(rq, owner) || task_current_selected(rq, owner)) { + exec_ctx =3D NULL; + break; + } + } + return exec_ctx; +} #else /* !CONFIG_SCHED_PROXY_EXEC */ static inline void do_activate_task(struct rq *rq, struct task_struct *p, int en_flags) diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c index 15e947a3ded7..53be78afdd07 100644 --- a/kernel/sched/cpupri.c +++ b/kernel/sched/cpupri.c @@ -96,12 +96,17 @@ static inline int __cpupri_find(struct cpupri *cp, stru= ct task_struct *p, if (skip) return 0; =20 - if (cpumask_any_and(&p->cpus_mask, vec->mask) >=3D nr_cpu_ids) + if ((p && cpumask_any_and(&p->cpus_mask, vec->mask) >=3D nr_cpu_ids) || + (!p && cpumask_any(vec->mask) >=3D nr_cpu_ids)) return 0; =20 if (lowest_mask) { - cpumask_and(lowest_mask, &p->cpus_mask, vec->mask); - cpumask_and(lowest_mask, lowest_mask, cpu_active_mask); + if (p) { + cpumask_and(lowest_mask, &p->cpus_mask, vec->mask); + cpumask_and(lowest_mask, lowest_mask, cpu_active_mask); + } else { + cpumask_copy(lowest_mask, vec->mask); + } =20 /* * We have to ensure that we have at least one bit diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 999bd17f11c4..21e56ac58e32 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1866,6 +1866,8 @@ static void migrate_task_rq_dl(struct task_struct *p,= int new_cpu __maybe_unused =20 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) { + struct task_struct *exec_ctx; + /* * Current can't be migrated, useless to reschedule, * let's hope p can move out. @@ -1874,12 +1876,16 @@ static void check_preempt_equal_dl(struct rq *rq, s= truct task_struct *p) !cpudl_find(&rq->rd->cpudl, rq_selected(rq), rq->curr, NULL)) return; =20 + exec_ctx =3D find_exec_ctx(rq, p); + if (task_current(rq, exec_ctx)) + return; + /* * p is migratable, so let's not schedule it and * see if it is pushed or pulled somewhere else. */ if (p->nr_cpus_allowed !=3D 1 && - cpudl_find(&rq->rd->cpudl, p, p, NULL)) + cpudl_find(&rq->rd->cpudl, p, exec_ctx, NULL)) return; =20 resched_curr(rq); @@ -2169,12 +2175,17 @@ static int find_later_rq(struct task_struct *sched_= ctx, struct task_struct *exec /* Locks the rq it finds */ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *= rq) { + struct task_struct *exec_ctx; struct rq *later_rq =3D NULL; int tries; int cpu; =20 for (tries =3D 0; tries < DL_MAX_TRIES; tries++) { - cpu =3D find_later_rq(task, task); + exec_ctx =3D find_exec_ctx(rq, task); + if (!exec_ctx) + break; + + cpu =3D find_later_rq(task, exec_ctx); =20 if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu)) break; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 6371b0fca4ad..f8134d062fa3 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1640,6 +1640,11 @@ static void check_preempt_equal_prio(struct rq *rq, = struct task_struct *p) !cpupri_find(&rq->rd->cpupri, rq_selected(rq), rq->curr, NULL)) return; =20 + /* No reason to preempt since rq->curr wouldn't change anyway */ + exec_ctx =3D find_exec_ctx(rq, p); + if (task_current(rq, exec_ctx)) + return; + /* * p is migratable, so let's not schedule it and * see if it is pushed or pulled somewhere else. @@ -1933,12 +1938,14 @@ static int find_lowest_rq(struct task_struct *sched= _ctx, struct task_struct *exe /* Will lock the rq it finds */ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq = *rq) { + struct task_struct *exec_ctx; struct rq *lowest_rq =3D NULL; int tries; int cpu; =20 for (tries =3D 0; tries < RT_MAX_TRIES; tries++) { - cpu =3D find_lowest_rq(task, task); + exec_ctx =3D find_exec_ctx(rq, task); + cpu =3D find_lowest_rq(task, exec_ctx); =20 if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu)) break; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ef3d327e267c..6cd473224cfe 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3564,6 +3564,16 @@ int task_is_pushable(struct rq *rq, struct task_stru= ct *p, int cpu) =20 return 0; } + +#ifdef CONFIG_SCHED_PROXY_EXEC +struct task_struct *find_exec_ctx(struct rq *rq, struct task_struct *p); +#else /* !CONFIG_SCHED_PROXY_EXEC */ +static inline +struct task_struct *find_exec_ctx(struct rq *rq, struct task_struct *p) +{ + return p; +} +#endif /* CONFIG_SCHED_PROXY_EXEC */ #endif =20 #endif /* _KERNEL_SCHED_SCHED_H */ --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BDEF5219E4 for ; Wed, 20 Dec 2023 00:19:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="3+mESWIH" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-6d64b546e7eso1791598b3a.2 for ; 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Tue, 19 Dec 2023 16:19:41 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:33 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-23-jstultz@google.com> Subject: [PATCH v7 22/23] sched: Refactor dl/rt find_lowest/latest_rq logic From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This pulls re-validation logic done in find_lowest_rq and find_latest_rq after re-acquiring the rq locks out into its own function. This allows us to later use a more complicated validation check for chain-migration when using proxy-exectuion. TODO: It seems likely we could consolidate this two functions further and leave the task_is_rt()/task_is_dl() checks externally? Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: John Stultz --- kernel/sched/deadline.c | 31 ++++++++++++++++++++----- kernel/sched/rt.c | 50 ++++++++++++++++++++++++++++------------- 2 files changed, 59 insertions(+), 22 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 21e56ac58e32..8b5701727342 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2172,6 +2172,30 @@ static int find_later_rq(struct task_struct *sched_c= tx, struct task_struct *exec return -1; } =20 +static inline bool dl_revalidate_rq_state(struct task_struct *task, struct= rq *rq, + struct rq *later) +{ + if (task_rq(task) !=3D rq) + return false; + + if (!cpumask_test_cpu(later->cpu, &task->cpus_mask)) + return false; + + if (task_on_cpu(rq, task)) + return false; + + if (!dl_task(task)) + return false; + + if (is_migration_disabled(task)) + return false; + + if (!task_on_rq_queued(task)) + return false; + + return true; +} + /* Locks the rq it finds */ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *= rq) { @@ -2204,12 +2228,7 @@ static struct rq *find_lock_later_rq(struct task_str= uct *task, struct rq *rq) =20 /* Retry if something changed. */ if (double_lock_balance(rq, later_rq)) { - if (unlikely(task_rq(task) !=3D rq || - !cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) || - task_on_cpu(rq, task) || - !dl_task(task) || - is_migration_disabled(task) || - !task_on_rq_queued(task))) { + if (unlikely(!dl_revalidate_rq_state(task, rq, later_rq))) { double_unlock_balance(rq, later_rq); later_rq =3D NULL; break; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index f8134d062fa3..fabb19891e95 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1935,6 +1935,39 @@ static int find_lowest_rq(struct task_struct *sched_= ctx, struct task_struct *exe return -1; } =20 +static inline bool rt_revalidate_rq_state(struct task_struct *task, struct= rq *rq, + struct rq *lowest) +{ + /* + * We had to unlock the run queue. In + * the mean time, task could have + * migrated already or had its affinity changed. + * Also make sure that it wasn't scheduled on its rq. + * It is possible the task was scheduled, set + * "migrate_disabled" and then got preempted, so we must + * check the task migration disable flag here too. + */ + if (task_rq(task) !=3D rq) + return false; + + if (!cpumask_test_cpu(lowest->cpu, &task->cpus_mask)) + return false; + + if (task_on_cpu(rq, task)) + return false; + + if (!rt_task(task)) + return false; + + if (is_migration_disabled(task)) + return false; + + if (!task_on_rq_queued(task)) + return false; + + return true; +} + /* Will lock the rq it finds */ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq = *rq) { @@ -1964,22 +1997,7 @@ static struct rq *find_lock_lowest_rq(struct task_st= ruct *task, struct rq *rq) =20 /* if the prio of this runqueue changed, try again */ if (double_lock_balance(rq, lowest_rq)) { - /* - * We had to unlock the run queue. In - * the mean time, task could have - * migrated already or had its affinity changed. - * Also make sure that it wasn't scheduled on its rq. - * It is possible the task was scheduled, set - * "migrate_disabled" and then got preempted, so we must - * check the task migration disable flag here too. - */ - if (unlikely(task_rq(task) !=3D rq || - !cpumask_test_cpu(lowest_rq->cpu, &task->cpus_mask) || - task_on_cpu(rq, task) || - !rt_task(task) || - is_migration_disabled(task) || - !task_on_rq_queued(task))) { - + if (unlikely(!rt_revalidate_rq_state(task, rq, lowest_rq))) { double_unlock_balance(rq, lowest_rq); lowest_rq =3D NULL; break; --=20 2.43.0.472.g3155946c3a-goog From nobody Fri Dec 19 12:29:09 2025 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3B9E221A13 for ; Wed, 20 Dec 2023 00:19:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="XxOnUhce" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dbd633c0653so1156004276.2 for ; Tue, 19 Dec 2023 16:19:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031584; x=1703636384; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=9eYR5qbdikZDN1oBPNGzkzAgPNV/qw7OTbW9wb9vboA=; b=XxOnUhce0kfXeWRYw1nLIgK7o5324Ed/X+0+KjAnofh0j1zbg19LZ7oP4uDXlOCYXx 3N+t/5qaXj+SLQeqxQyG45rM9bDbaAwfDjlyVAwj7y9Igiu8kEpk1t5AW6Vbr984OJjf p2NqPWZVb5AdicE8ErWFPgKNCewXHdnJIRyWgGL9qr1e4t9ThNYh4DqDUbjfvMFtVO9n 7ar8rr4z/uSH6TuDW9Nd5G9jQWS97UG7fjpzQk7svtbVTPrM3uwkxiLruSCfQdKIqZ7n Hiw+QHW3pU9Ce4YZSOxqlQ1web1iSTM5rxkuY66uOEfN1V65SvduBmxkyb0u5++dVk5D 30jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031584; x=1703636384; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=9eYR5qbdikZDN1oBPNGzkzAgPNV/qw7OTbW9wb9vboA=; b=pjultZKcpVXCYg7ez1duYglOOjV4uslU7046Pzxx3pJ6IVs/SNVl4tM7RLbchcVE+9 3qtPfN7vhE5WBJkvpZXHADttdclbs79iSYMIIcmExxo+LgD5o5IBSG2VB+SZn1SGKuLU FAlAhjHe+JWSecqthK3zF7lHjGbDzeXooTi9UUEpurtBKq0EirXlx7OZk64RP/wtdQ4y ItwhdvcqbN8HNy4d/jYtROwHYHJx9d2tM4X/bK4T9DFUcjiiHSsb2ZZukDhMBcGmwnE7 Twg0Mecq4Qf6enwtHWPYABB53lATB89mr7/tE9CdL/7JMiwz+sUr6f5Uv6Pd5s7IqXbN HWxw== X-Gm-Message-State: AOJu0YwXzqAeVBWcg2cM7q1NPMnYudxxi1kU3Th3AdIzkGESy4Ucv8+Y 83GN6y0uwCT99R7XJ4OI3XgV0/R6QSO6cmH1BsmyVbRonjTrIg85KSwLWrE/Zs5xQkhNvnmzcB4 UgEmtdmebpVqWSNbDGoerBlfXzLl01aRZ2zfPn98rb0d/3u+eOVhtWN+6o185LDGxUb+rj5s= X-Google-Smtp-Source: AGHT+IGNvVRiBHexgmK7zRXAjEe1CDQbDcE3HIznszSjmFp3r7JGWbSksNYb3I+GPQ5aFlbcJoRJA08ZXSjn X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6902:134a:b0:dbd:2f0:c763 with SMTP id g10-20020a056902134a00b00dbd02f0c763mr244149ybu.1.1703031583592; Tue, 19 Dec 2023 16:19:43 -0800 (PST) Date: Tue, 19 Dec 2023 16:18:34 -0800 In-Reply-To: <20231220001856.3710363-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231220001856.3710363-1-jstultz@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231220001856.3710363-24-jstultz@google.com> Subject: [PATCH v7 23/23] sched: Fix rt/dl load balancing via chain level balance From: John Stultz To: LKML Cc: "Connor O'Brien" , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Youssef Esmat , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , kernel-team@android.com, John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Connor O'Brien RT/DL balancing is supposed to guarantee that with N cpus available & CPU affinity permitting, the top N RT/DL tasks will get spread across the CPUs and all get to run. Proxy exec greatly complicates this as blocked tasks remain on the rq but cannot be usefully migrated away from their lock owning tasks. This has two major consequences: 1. In order to get the desired properties we need to migrate a blocked task, its would-be proxy, and everything in between, all together - i.e., we need to push/pull "blocked chains" rather than individual tasks. 2. Tasks that are part of rq->curr's "blocked tree" therefore should not be pushed or pulled. Options for enforcing this seem to include a) create some sort of complex data structure for tracking pushability, updating it whenever the blocked tree for rq->curr changes (e.g. on mutex handoffs, migrations, etc.) as well as on context switches. b) give up on O(1) pushability checks, and search through the pushable list every push/pull until we find a pushable "chain" c) Extend option "b" with some sort of caching to avoid repeated work. For the sake of simplicity & separating the "chain level balancing" concerns from complicated optimizations, this patch focuses on trying to implement option "b" correctly. This can then hopefully provide a baseline for "correct load balancing behavior" that optimizations can try to implement more efficiently. Note: The inability to atomically check "is task enqueued on a specific rq" creates 2 possible races when following a blocked chain: - If we check task_rq() first on a task that is dequeued from its rq, it can be woken and enqueued on another rq before the call to task_on_rq_queued() - If we call task_on_rq_queued() first on a task that is on another rq, it can be dequeued (since we don't hold its rq's lock) and then be set to the current rq before we check task_rq(). Maybe there's a more elegant solution that would work, but for now, just sandwich the task_rq() check between two task_on_rq_queued() checks, all separated by smp_rmb() calls. Since we hold rq's lock, task can't be enqueued or dequeued from rq, so neither race should be possible. extensive comments on various pitfalls, races, etc. included inline. This patch was broken out from a larger chain migration patch originally by Connor O'Brien. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Youssef Esmat Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: kernel-team@android.com Signed-off-by: Connor O'Brien [jstultz: split out from larger chain migration patch, majorly refactored for runtime conditionalization] Signed-off-by: John Stultz --- v7: * Split out from larger chain-migration patch in earlier versions of this series * Larger rework to allow proper conditionalization of the logic when running with CONFIG_SCHED_PROXY_EXEC --- kernel/sched/core.c | 77 +++++++++++++++++++++++- kernel/sched/deadline.c | 98 +++++++++++++++++++++++------- kernel/sched/rt.c | 130 ++++++++++++++++++++++++++++++++-------- kernel/sched/sched.h | 18 +++++- 4 files changed, 273 insertions(+), 50 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 77a79d5f829a..30dfb6f14f2b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3923,7 +3923,6 @@ struct task_struct *find_exec_ctx(struct rq *rq, stru= ct task_struct *p) return p; =20 lockdep_assert_rq_held(rq); - for (exec_ctx =3D p; task_is_blocked(exec_ctx) && !task_on_cpu(rq, exec_c= tx); exec_ctx =3D owner) { mutex =3D exec_ctx->blocked_on; @@ -3938,6 +3937,82 @@ struct task_struct *find_exec_ctx(struct rq *rq, str= uct task_struct *p) } return exec_ctx; } + +#ifdef CONFIG_SMP +void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task) +{ + struct task_struct *owner; + + if (!sched_proxy_exec()) { + __push_task_chain(rq, dst_rq, task); + return; + } + + lockdep_assert_rq_held(rq); + lockdep_assert_rq_held(dst_rq); + + BUG_ON(!task_queued_on_rq(rq, task)); + BUG_ON(task_current_selected(rq, task)); + + while (task) { + if (!task_queued_on_rq(rq, task) || task_current_selected(rq, task)) + break; + + if (task_is_blocked(task)) + owner =3D __mutex_owner(task->blocked_on); + else + owner =3D NULL; + __push_task_chain(rq, dst_rq, task); + if (task =3D=3D owner) + break; + task =3D owner; + } +} + +/* + * Returns: + * 1 if chain is pushable and affinity does not prevent pushing to cpu + * 0 if chain is unpushable + * -1 if chain is pushable but affinity blocks running on cpu. + */ +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu) +{ + struct task_struct *exec_ctx; + + if (!sched_proxy_exec()) + return __task_is_pushable(rq, p, cpu); + + lockdep_assert_rq_held(rq); + + if (task_rq(p) !=3D rq || !task_on_rq_queued(p)) + return 0; + + exec_ctx =3D find_exec_ctx(rq, p); + /* + * Chain leads off the rq, we're free to push it anywhere. + * + * One wrinkle with relying on find_exec_ctx is that when the chain + * leads to a task currently migrating to rq, we see the chain as + * pushable & push everything prior to the migrating task. Even if + * we checked explicitly for this case, we could still race with a + * migration after the check. + * This shouldn't permanently produce a bad state though, as proxy() + * will send the chain back to rq and by that point the migration + * should be complete & a proper push can occur. + */ + if (!exec_ctx) + return 1; + + if (task_on_cpu(rq, exec_ctx) || exec_ctx->nr_cpus_allowed <=3D 1) + return 0; + + return cpumask_test_cpu(cpu, &exec_ctx->cpus_mask) ? 1 : -1; +} +#else /* !CONFIG_SMP */ +void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task) +{ +} +#endif /* CONFIG_SMP */ #else /* !CONFIG_SCHED_PROXY_EXEC */ static inline void do_activate_task(struct rq *rq, struct task_struct *p, int en_flags) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 8b5701727342..b7be888c1635 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2172,8 +2172,77 @@ static int find_later_rq(struct task_struct *sched_c= tx, struct task_struct *exec return -1; } =20 +static struct task_struct *pick_next_pushable_dl_task(struct rq *rq) +{ + struct task_struct *p =3D NULL; + struct rb_node *next_node; + + if (!has_pushable_dl_tasks(rq)) + return NULL; + + next_node =3D rb_first_cached(&rq->dl.pushable_dl_tasks_root); + +next_node: + if (next_node) { + p =3D __node_2_pdl(next_node); + + /* + * cpu argument doesn't matter because we treat a -1 result + * (pushable but can't go to cpu0) the same as a 1 result + * (pushable to cpu0). All we care about here is general + * pushability. + */ + if (task_is_pushable(rq, p, 0)) + return p; + + next_node =3D rb_next(next_node); + goto next_node; + } + + if (!p) + return NULL; + + WARN_ON_ONCE(rq->cpu !=3D task_cpu(p)); + WARN_ON_ONCE(task_current(rq, p)); + WARN_ON_ONCE(p->nr_cpus_allowed <=3D 1); + + WARN_ON_ONCE(!task_on_rq_queued(p)); + WARN_ON_ONCE(!dl_task(p)); + + return p; +} + +#ifdef CONFIG_SCHED_PROXY_EXEC static inline bool dl_revalidate_rq_state(struct task_struct *task, struct= rq *rq, - struct rq *later) + struct rq *later, bool *retry) +{ + if (!dl_task(task) || is_migration_disabled(task)) + return false; + + if (rq !=3D this_rq()) { + struct task_struct *next_task =3D pick_next_pushable_dl_task(rq); + + if (next_task =3D=3D task) { + struct task_struct *exec_ctx; + + exec_ctx =3D find_exec_ctx(rq, next_task); + *retry =3D (exec_ctx && !cpumask_test_cpu(later->cpu, + &exec_ctx->cpus_mask)); + } else { + return false; + } + } else { + int pushable =3D task_is_pushable(rq, task, later->cpu); + + *retry =3D pushable =3D=3D -1; + if (!pushable) + return false; + } + return true; +} +#else +static inline bool dl_revalidate_rq_state(struct task_struct *task, struct= rq *rq, + struct rq *later, bool *retry) { if (task_rq(task) !=3D rq) return false; @@ -2195,16 +2264,18 @@ static inline bool dl_revalidate_rq_state(struct ta= sk_struct *task, struct rq *r =20 return true; } - +#endif /* Locks the rq it finds */ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *= rq) { struct task_struct *exec_ctx; struct rq *later_rq =3D NULL; + bool retry; int tries; int cpu; =20 for (tries =3D 0; tries < DL_MAX_TRIES; tries++) { + retry =3D false; exec_ctx =3D find_exec_ctx(rq, task); if (!exec_ctx) break; @@ -2228,7 +2299,7 @@ static struct rq *find_lock_later_rq(struct task_stru= ct *task, struct rq *rq) =20 /* Retry if something changed. */ if (double_lock_balance(rq, later_rq)) { - if (unlikely(!dl_revalidate_rq_state(task, rq, later_rq))) { + if (unlikely(!dl_revalidate_rq_state(task, rq, later_rq, &retry))) { double_unlock_balance(rq, later_rq); later_rq =3D NULL; break; @@ -2240,7 +2311,7 @@ static struct rq *find_lock_later_rq(struct task_stru= ct *task, struct rq *rq) * its earliest one has a later deadline than our * task, the rq is a good one. */ - if (dl_task_is_earliest_deadline(task, later_rq)) + if (!retry && dl_task_is_earliest_deadline(task, later_rq)) break; =20 /* Otherwise we try again. */ @@ -2251,25 +2322,6 @@ static struct rq *find_lock_later_rq(struct task_str= uct *task, struct rq *rq) return later_rq; } =20 -static struct task_struct *pick_next_pushable_dl_task(struct rq *rq) -{ - struct task_struct *p; - - if (!has_pushable_dl_tasks(rq)) - return NULL; - - p =3D __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root)); - - WARN_ON_ONCE(rq->cpu !=3D task_cpu(p)); - WARN_ON_ONCE(task_current(rq, p)); - WARN_ON_ONCE(p->nr_cpus_allowed <=3D 1); - - WARN_ON_ONCE(!task_on_rq_queued(p)); - WARN_ON_ONCE(!dl_task(p)); - - return p; -} - /* * See if the non running -deadline tasks on this rq * can be sent to some other CPU where they can preempt diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index fabb19891e95..d5ce95dc5c09 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1935,8 +1935,108 @@ static int find_lowest_rq(struct task_struct *sched= _ctx, struct task_struct *exe return -1; } =20 +static struct task_struct *pick_next_pushable_task(struct rq *rq) +{ + struct plist_head *head =3D &rq->rt.pushable_tasks; + struct task_struct *p, *push_task =3D NULL; + + if (!has_pushable_tasks(rq)) + return NULL; + + plist_for_each_entry(p, head, pushable_tasks) { + if (task_is_pushable(rq, p, 0)) { + push_task =3D p; + break; + } + } + + if (!push_task) + return NULL; + + BUG_ON(rq->cpu !=3D task_cpu(push_task)); + BUG_ON(task_current(rq, push_task) || task_current_selected(rq, push_task= )); + BUG_ON(!task_on_rq_queued(push_task)); + BUG_ON(!rt_task(push_task)); + + return p; +} + +#ifdef CONFIG_SCHED_PROXY_EXEC +static inline bool rt_revalidate_rq_state(struct task_struct *task, struct= rq *rq, + struct rq *lowest, bool *retry) +{ + /* + * Releasing the rq lock means we need to re-check pushability. + * Some scenarios: + * 1) If a migration from another CPU sent a task/chain to rq + * that made task newly unpushable by completing a chain + * from task to rq->curr, then we need to bail out and push something + * else. + * 2) If our chain led off this CPU or to a dequeued task, the last waiter + * on this CPU might have acquired the lock and woken (or even migrated + * & run, handed off the lock it held, etc...). This can invalidate the + * result of find_lowest_rq() if our chain previously ended in a block= ed + * task whose affinity we could ignore, but now ends in an unblocked + * task that can't run on lowest_rq. + * 3) Race described at https://lore.kernel.org/all/1523536384-26781-2-gi= t-send-email-huawei.libin@huawei.com/ + * + * Notes on these: + * - Scenario #2 is properly handled by rerunning find_lowest_rq + * - Scenario #1 requires that we fail + * - Scenario #3 can AFAICT only occur when rq is not this_rq(). And the + * suggested fix is not universally correct now that push_cpu_stop() can + * call this function. + */ + if (!rt_task(task) || is_migration_disabled(task)) { + return false; + } else if (rq !=3D this_rq()) { + /* + * If we are dealing with a remote rq, then all bets are off + * because task might have run & then been dequeued since we + * released the lock, at which point our normal checks can race + * with migration, as described in + * https://lore.kernel.org/all/1523536384-26781-2-git-send-email-huawei.= libin@huawei.com/ + * Need to repick to ensure we avoid a race. + * But re-picking would be unnecessary & incorrect in the + * push_cpu_stop() path. + */ + struct task_struct *next_task =3D pick_next_pushable_task(rq); + + if (next_task =3D=3D task) { + struct task_struct *exec_ctx; + + exec_ctx =3D find_exec_ctx(rq, next_task); + *retry =3D (exec_ctx && + !cpumask_test_cpu(lowest->cpu, + &exec_ctx->cpus_mask)); + } else { + return false; + } + } else { + /* + * Chain level balancing introduces new ways for our choice of + * task & rq to become invalid when we release the rq lock, e.g.: + * 1) Migration to rq from another CPU makes task newly unpushable + * by completing a "blocked chain" from task to rq->curr. + * Fail so a different task can be chosen for push. + * 2) In cases where task's blocked chain led to a dequeued task + * or one on another rq, the last waiter in the chain on this + * rq might have acquired the lock and woken, meaning we must + * pick a different rq if its affinity prevents running on + * lowest rq. + */ + int pushable =3D task_is_pushable(rq, task, lowest->cpu); + + *retry =3D pushable =3D=3D -1; + if (!pushable) + return false; + } + + return true; +} +#else /* !CONFIG_SCHED_PROXY_EXEC */ static inline bool rt_revalidate_rq_state(struct task_struct *task, struct= rq *rq, - struct rq *lowest) + struct rq *lowest, bool *retry) { /* * We had to unlock the run queue. In @@ -1967,16 +2067,19 @@ static inline bool rt_revalidate_rq_state(struct ta= sk_struct *task, struct rq *r =20 return true; } +#endif =20 /* Will lock the rq it finds */ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq = *rq) { struct task_struct *exec_ctx; struct rq *lowest_rq =3D NULL; + bool retry; int tries; int cpu; =20 for (tries =3D 0; tries < RT_MAX_TRIES; tries++) { + retry =3D false; exec_ctx =3D find_exec_ctx(rq, task); cpu =3D find_lowest_rq(task, exec_ctx); =20 @@ -1997,7 +2100,7 @@ static struct rq *find_lock_lowest_rq(struct task_str= uct *task, struct rq *rq) =20 /* if the prio of this runqueue changed, try again */ if (double_lock_balance(rq, lowest_rq)) { - if (unlikely(!rt_revalidate_rq_state(task, rq, lowest_rq))) { + if (unlikely(!rt_revalidate_rq_state(task, rq, lowest_rq, &retry))) { double_unlock_balance(rq, lowest_rq); lowest_rq =3D NULL; break; @@ -2005,7 +2108,7 @@ static struct rq *find_lock_lowest_rq(struct task_str= uct *task, struct rq *rq) } =20 /* If this rq is still suitable use it. */ - if (lowest_rq->rt.highest_prio.curr > task->prio) + if (lowest_rq->rt.highest_prio.curr > task->prio && !retry) break; =20 /* try again */ @@ -2016,27 +2119,6 @@ static struct rq *find_lock_lowest_rq(struct task_st= ruct *task, struct rq *rq) return lowest_rq; } =20 -static struct task_struct *pick_next_pushable_task(struct rq *rq) -{ - struct task_struct *p; - - if (!has_pushable_tasks(rq)) - return NULL; - - p =3D plist_first_entry(&rq->rt.pushable_tasks, - struct task_struct, pushable_tasks); - - BUG_ON(rq->cpu !=3D task_cpu(p)); - BUG_ON(task_current(rq, p)); - BUG_ON(task_current_selected(rq, p)); - BUG_ON(p->nr_cpus_allowed <=3D 1); - - BUG_ON(!task_on_rq_queued(p)); - BUG_ON(!rt_task(p)); - - return p; -} - /* * If the current CPU has more than one RT task, see if the non * running task can migrate over to a CPU that is running a task diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 6cd473224cfe..4b97b36be691 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3548,7 +3548,7 @@ extern u64 avg_vruntime(struct cfs_rq *cfs_rq); extern int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se); #ifdef CONFIG_SMP static inline -void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task) +void __push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struc= t *task) { deactivate_task(rq, task, 0); set_task_cpu(task, dst_rq->cpu); @@ -3556,7 +3556,7 @@ void push_task_chain(struct rq *rq, struct rq *dst_rq= , struct task_struct *task) } =20 static inline -int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu) +int __task_is_pushable(struct rq *rq, struct task_struct *p, int cpu) { if (!task_on_cpu(rq, p) && cpumask_test_cpu(cpu, &p->cpus_mask)) @@ -3566,8 +3566,22 @@ int task_is_pushable(struct rq *rq, struct task_stru= ct *p, int cpu) } =20 #ifdef CONFIG_SCHED_PROXY_EXEC +void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task); +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu); struct task_struct *find_exec_ctx(struct rq *rq, struct task_struct *p); #else /* !CONFIG_SCHED_PROXY_EXEC */ +static inline +void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct = *task) +{ + __push_task_chain(rq, dst_rq, task); +} + +static inline +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu) +{ + return __task_is_pushable(rq, p, cpu); +} + static inline struct task_struct *find_exec_ctx(struct rq *rq, struct task_struct *p) { --=20 2.43.0.472.g3155946c3a-goog