From nobody Fri Dec 19 14:13:28 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; 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="kwDq0Ae1" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dbd4ed0b4d4so2258910276.3 for ; Tue, 19 Dec 2023 16:19:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1703031562; x=1703636362; 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=1WvcOEd7dBy/nEtXMgBcYnJnQJnDQmfBeveDTN2lf28=; b=kwDq0Ae1Hr8XjyAoSWzUUQeLofbHyhG8PyIqE64GFejoy/mYCAIhMTTOeWDOI4uECZ B4DIRz480AqKgR3Bpzs/oTPaZtCef27C5uJYW/8SPTLeHmWzg/bYzfODpj4HILrnnnkp EgN9iE7zJ3qnkV7NZW7x3L9fb6gY7GKFmV4ciq04t7T6yzngYhvdaj3fRsetuuGvzAJi g8VN3PUL1g0YOOrIeBuyQW/vty3SMWKY8uDnqmRjuyfOd9YJsObVzDxQscvLnGiiqJGX 0ykkdP/74ntuAgV5q6nh3H+HOLs/0EoYAjyz4kjwRMruOscpri7HgU9EOEh7LnaqEcuS i2RA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703031562; x=1703636362; 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=1WvcOEd7dBy/nEtXMgBcYnJnQJnDQmfBeveDTN2lf28=; b=GhLTEiH6kOBRU/14ule/RZlYTFPrYaKMJuEKd5bzRjRvcAIXyKh3INs9Wp/MXlIeQZ N/r7Mm+RpK0j8fOjDaEVhFxeMwIRNu0Em+7QBBpjxpUBnxKKMKWSar8dIt74vuvNHAin hTc9KmiBM0PKdBGnfA4NdruuQw7lJLyfVGYRqtxAM3+2p6bOChd3G7/VjGmlS+Ubbjsp OmGO2VyMlJJyoTa/wb2Q39Fh1RWsCND2heSRo1MJoCVwkRX3vomaZxqM5xaem77XHK7q 4gvmqbuGXmZnBdoHFlNyj6lgvJys5dZCWRmgo6vRIX7m5Nz661vmcLio8LaYetNg+VjB Rm5w== X-Gm-Message-State: AOJu0Yxm9L6UfHLYWlVX7Sh7qlI8pHCV2gxPyICj5++N1eOZ/wrfdLu5 Z1SS9jLtgH/qwfC4KxI247QfNac0WGakJfNV20ss5WQ+fzbTXBCdlvK+BINjWXetN39CBbi/xJf RRs6euFuGty4G7gBEZw1OtflWlNbRrCE5URHG1+g+dQwPLi769WkjDM1gLUBiqFkOjtqb4sA= X-Google-Smtp-Source: AGHT+IHc9/8Lf1jyH+8Jf0HA6MLUdz+aT92t7ijdANyAVcJ0S1YNpEf15c5RUtVNt0psspRc4f7zsVHG2kqy X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6902:54f:b0:dbd:5a7f:6b38 with SMTP id z15-20020a056902054f00b00dbd5a7f6b38mr533918ybs.12.1703031561931; 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