From nobody Mon Feb 9 18:59:53 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A38C26A0AD; Mon, 6 Oct 2025 10:46:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759747564; cv=none; b=WcLdNCEX6JCXOvZn6UO5sMGFJUgOf5l4vZrwKUfmbWL8PbHnv2D53Y1YnKFhPnQVoUHSkHi5w2mWGS+RpYzVi+V5PnT78yEdz3g4j6rgu17n8CPnwull0+EmUJMc60k2GJbp1k0scyFFmRpaJ1DvW+bPii3V1zTiHhOIb66w8zs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759747564; c=relaxed/simple; bh=uoGVd06lq2eF3hcvvzxnLHE/hF6e2Zz4st/hy0x5MHo=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=irII5RkaSLZOn7zxeul2yntkChH9yPQO1UiJJlfBuAUzFRgV/mMmcQxXovgiBn/4wCdpkmF6VXn6bzDSErt+QZUfx0tAZUy4clXDc19QI1FftWSba3Kqlj1Q+SErPbHFSTdF5KVbwkoQq9ZgavSO5XDNIfvgObRilJqdugsvTMs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=gD48spt2; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="gD48spt2" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=ATdxrEudMk6ySd+MumMvxmM6SQe/dD5bbpX5J10MovI=; b=gD48spt2BTZNgJn5zHCLeJfQtj sWEUdVe2P4LXAZ7ay+Ns8WyBBhBgdvrtdoPV554iJJcNFqzBINCiG7WTL6XeP0/yRJUEo5ptqMCEC yUCQfej5b5QJrnNeztgiybdrdpFhggJSaMgnnWLWi+MzOaKylisrzivfQ4vVvvdG79DwoKOWS3X0z GRiXyGX4RIUspUODH6aq077QhzrUpDSsiieDaDXyWzHTLazAZGRZsXpAsrymhI2P7a2UgnPBm+fqd r6wHBMrYWwe2QXnPH/91FuqUjCdGqd2uHOMvgJRC95LGaTAHO1rQoB7LpsqpAMPUWN7a5fi+dYchT qurqmC9Q==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1v5iiy-0000000Grdn-3KFS; Mon, 06 Oct 2025 10:45:49 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id BEE2A300289; Mon, 06 Oct 2025 12:45:47 +0200 (CEST) Message-ID: <20251006104526.613879143@infradead.org> User-Agent: quilt/0.68 Date: Mon, 06 Oct 2025 12:44:03 +0200 From: Peter Zijlstra To: tj@kernel.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, longman@redhat.com, hannes@cmpxchg.org, mkoutny@suse.com, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, cgroups@vger.kernel.org, sched-ext@lists.linux.dev, liuwenfang@honor.com, tglx@linutronix.de Subject: [PATCH 01/12] sched: Employ sched_change guards References: <20251006104402.946760805@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As proposed a long while ago -- and half done by scx -- wrap the scheduler's 'change' pattern in a guard helper. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Tejun Heo --- include/linux/cleanup.h | 5 + kernel/sched/core.c | 157 ++++++++++++++++++-------------------------= ----- kernel/sched/ext.c | 39 +++++------ kernel/sched/sched.h | 21 +++--- kernel/sched/syscalls.c | 65 +++++++------------ 5 files changed, 116 insertions(+), 171 deletions(-) --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -340,6 +340,11 @@ _label: #define __DEFINE_CLASS_IS_CONDITIONAL(_name, _is_cond) \ static __maybe_unused const bool class_##_name##_is_conditional =3D _is_co= nd =20 +#define DEFINE_CLASS_IS_UNCONDITIONAL(_name) \ + __DEFINE_CLASS_IS_CONDITIONAL(_name, false); \ + static inline void * class_##_name##_lock_ptr(class_##_name##_t *_T) \ + { return (void *)1; } + #define __GUARD_IS_ERR(_ptr) \ ({ \ unsigned long _rc =3D (__force unsigned long)(_ptr); \ --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7326,7 +7326,7 @@ void rt_mutex_post_schedule(void) */ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) { - int prio, oldprio, queued, running, queue_flag =3D + int prio, oldprio, queue_flag =3D DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; const struct sched_class *prev_class, *next_class; struct rq_flags rf; @@ -7391,52 +7391,42 @@ void rt_mutex_setprio(struct task_struct if (prev_class !=3D next_class && p->se.sched_delayed) dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK); =20 - queued =3D task_on_rq_queued(p); - running =3D task_current_donor(rq, p); - if (queued) - dequeue_task(rq, p, queue_flag); - if (running) - put_prev_task(rq, p); - - /* - * Boosting condition are: - * 1. -rt task is running and holds mutex A - * --> -dl task blocks on mutex A - * - * 2. -dl task is running and holds mutex A - * --> -dl task blocks on mutex A and could preempt the - * running task - */ - if (dl_prio(prio)) { - if (!dl_prio(p->normal_prio) || - (pi_task && dl_prio(pi_task->prio) && - dl_entity_preempt(&pi_task->dl, &p->dl))) { - p->dl.pi_se =3D pi_task->dl.pi_se; - queue_flag |=3D ENQUEUE_REPLENISH; + scoped_guard (sched_change, p, queue_flag) { + /* + * Boosting condition are: + * 1. -rt task is running and holds mutex A + * --> -dl task blocks on mutex A + * + * 2. -dl task is running and holds mutex A + * --> -dl task blocks on mutex A and could preempt the + * running task + */ + if (dl_prio(prio)) { + if (!dl_prio(p->normal_prio) || + (pi_task && dl_prio(pi_task->prio) && + dl_entity_preempt(&pi_task->dl, &p->dl))) { + p->dl.pi_se =3D pi_task->dl.pi_se; + scope->flags |=3D ENQUEUE_REPLENISH; + } else { + p->dl.pi_se =3D &p->dl; + } + } else if (rt_prio(prio)) { + if (dl_prio(oldprio)) + p->dl.pi_se =3D &p->dl; + if (oldprio < prio) + scope->flags |=3D ENQUEUE_HEAD; } else { - p->dl.pi_se =3D &p->dl; + if (dl_prio(oldprio)) + p->dl.pi_se =3D &p->dl; + if (rt_prio(oldprio)) + p->rt.timeout =3D 0; } - } else if (rt_prio(prio)) { - if (dl_prio(oldprio)) - p->dl.pi_se =3D &p->dl; - if (oldprio < prio) - queue_flag |=3D ENQUEUE_HEAD; - } else { - if (dl_prio(oldprio)) - p->dl.pi_se =3D &p->dl; - if (rt_prio(oldprio)) - p->rt.timeout =3D 0; - } =20 - p->sched_class =3D next_class; - p->prio =3D prio; + p->sched_class =3D next_class; + p->prio =3D prio; =20 - check_class_changing(rq, p, prev_class); - - if (queued) - enqueue_task(rq, p, queue_flag); - if (running) - set_next_task(rq, p); + check_class_changing(rq, p, prev_class); + } =20 check_class_changed(rq, p, prev_class, oldprio); out_unlock: @@ -8084,26 +8074,9 @@ int migrate_task_to(struct task_struct * */ void sched_setnuma(struct task_struct *p, int nid) { - bool queued, running; - struct rq_flags rf; - struct rq *rq; - - rq =3D task_rq_lock(p, &rf); - queued =3D task_on_rq_queued(p); - running =3D task_current_donor(rq, p); - - if (queued) - dequeue_task(rq, p, DEQUEUE_SAVE); - if (running) - put_prev_task(rq, p); - - p->numa_preferred_nid =3D nid; - - if (queued) - enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - if (running) - set_next_task(rq, p); - task_rq_unlock(rq, p, &rf); + guard(task_rq_lock)(p); + scoped_guard (sched_change, p, DEQUEUE_SAVE) + p->numa_preferred_nid =3D nid; } #endif /* CONFIG_NUMA_BALANCING */ =20 @@ -9205,8 +9178,9 @@ static void sched_change_group(struct ta */ void sched_move_task(struct task_struct *tsk, bool for_autogroup) { - int queued, running, queue_flags =3D + unsigned int queue_flags =3D DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; + bool resched =3D false; struct rq *rq; =20 CLASS(task_rq_lock, rq_guard)(tsk); @@ -9214,29 +9188,16 @@ void sched_move_task(struct task_struct =20 update_rq_clock(rq); =20 - running =3D task_current_donor(rq, tsk); - queued =3D task_on_rq_queued(tsk); + scoped_guard (sched_change, tsk, queue_flags) { + sched_change_group(tsk); + if (!for_autogroup) + scx_cgroup_move_task(tsk); + if (scope->running) + resched =3D true; + } =20 - if (queued) - dequeue_task(rq, tsk, queue_flags); - if (running) - put_prev_task(rq, tsk); - - sched_change_group(tsk); - if (!for_autogroup) - scx_cgroup_move_task(tsk); - - if (queued) - enqueue_task(rq, tsk, queue_flags); - if (running) { - set_next_task(rq, tsk); - /* - * After changing group, the running task may have joined a - * throttled one but it's still the running task. Trigger a - * resched to make sure that task can still run. - */ + if (resched) resched_curr(rq); - } } =20 static struct cgroup_subsys_state * @@ -10892,37 +10853,39 @@ void sched_mm_cid_fork(struct task_struc } #endif /* CONFIG_SCHED_MM_CID */ =20 -#ifdef CONFIG_SCHED_CLASS_EXT -void sched_deq_and_put_task(struct task_struct *p, int queue_flags, - struct sched_enq_and_set_ctx *ctx) +static DEFINE_PER_CPU(struct sched_change_ctx, sched_change_ctx); + +struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigne= d int flags) { + struct sched_change_ctx *ctx =3D this_cpu_ptr(&sched_change_ctx); struct rq *rq =3D task_rq(p); =20 lockdep_assert_rq_held(rq); =20 - *ctx =3D (struct sched_enq_and_set_ctx){ + *ctx =3D (struct sched_change_ctx){ .p =3D p, - .queue_flags =3D queue_flags, + .flags =3D flags, .queued =3D task_on_rq_queued(p), .running =3D task_current(rq, p), }; =20 - update_rq_clock(rq); if (ctx->queued) - dequeue_task(rq, p, queue_flags | DEQUEUE_NOCLOCK); + dequeue_task(rq, p, flags); if (ctx->running) put_prev_task(rq, p); + + return ctx; } =20 -void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx) +void sched_change_end(struct sched_change_ctx *ctx) { - struct rq *rq =3D task_rq(ctx->p); + struct task_struct *p =3D ctx->p; + struct rq *rq =3D task_rq(p); =20 lockdep_assert_rq_held(rq); =20 if (ctx->queued) - enqueue_task(rq, ctx->p, ctx->queue_flags | ENQUEUE_NOCLOCK); + enqueue_task(rq, p, ctx->flags | ENQUEUE_NOCLOCK); if (ctx->running) - set_next_task(rq, ctx->p); + set_next_task(rq, p); } -#endif /* CONFIG_SCHED_CLASS_EXT */ --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -3780,11 +3780,10 @@ static void scx_bypass(bool bypass) */ list_for_each_entry_safe_reverse(p, n, &rq->scx.runnable_list, scx.runnable_node) { - struct sched_enq_and_set_ctx ctx; - /* cycling deq/enq is enough, see the function comment */ - sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx); - sched_enq_and_set_task(&ctx); + scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE) { + /* nothing */ ; + } } =20 /* resched to restore ticks and idle state */ @@ -3916,17 +3915,16 @@ static void scx_disable_workfn(struct kt const struct sched_class *old_class =3D p->sched_class; const struct sched_class *new_class =3D __setscheduler_class(p->policy, p->prio); - struct sched_enq_and_set_ctx ctx; - - if (old_class !=3D new_class && p->se.sched_delayed) - dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); =20 - sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx); + update_rq_clock(task_rq(p)); =20 - p->sched_class =3D new_class; - check_class_changing(task_rq(p), p, old_class); + if (old_class !=3D new_class && p->se.sched_delayed) + dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_N= OCLOCK); =20 - sched_enq_and_set_task(&ctx); + scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOC= LOCK) { + p->sched_class =3D new_class; + check_class_changing(task_rq(p), p, old_class); + } =20 check_class_changed(task_rq(p), p, old_class, p->prio); scx_exit_task(p); @@ -4660,21 +4658,20 @@ static int scx_enable(struct sched_ext_o const struct sched_class *old_class =3D p->sched_class; const struct sched_class *new_class =3D __setscheduler_class(p->policy, p->prio); - struct sched_enq_and_set_ctx ctx; =20 if (!tryget_task_struct(p)) continue; =20 - if (old_class !=3D new_class && p->se.sched_delayed) - dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); - - sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx); + update_rq_clock(task_rq(p)); =20 - p->scx.slice =3D SCX_SLICE_DFL; - p->sched_class =3D new_class; - check_class_changing(task_rq(p), p, old_class); + if (old_class !=3D new_class && p->se.sched_delayed) + dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_N= OCLOCK); =20 - sched_enq_and_set_task(&ctx); + scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOC= LOCK) { + p->scx.slice =3D SCX_SLICE_DFL; + p->sched_class =3D new_class; + check_class_changing(task_rq(p), p, old_class); + } =20 check_class_changed(task_rq(p), p, old_class, p->prio); put_task_struct(p); --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3885,23 +3885,22 @@ extern void check_class_changed(struct r extern struct balance_callback *splice_balance_callbacks(struct rq *rq); extern void balance_callbacks(struct rq *rq, struct balance_callback *head= ); =20 -#ifdef CONFIG_SCHED_CLASS_EXT -/* - * Used by SCX in the enable/disable paths to move tasks between sched_cla= sses - * and establish invariants. - */ -struct sched_enq_and_set_ctx { +struct sched_change_ctx { struct task_struct *p; - int queue_flags; + int flags; bool queued; bool running; }; =20 -void sched_deq_and_put_task(struct task_struct *p, int queue_flags, - struct sched_enq_and_set_ctx *ctx); -void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx); +struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigne= d int flags); +void sched_change_end(struct sched_change_ctx *ctx); =20 -#endif /* CONFIG_SCHED_CLASS_EXT */ +DEFINE_CLASS(sched_change, struct sched_change_ctx *, + sched_change_end(_T), + sched_change_begin(p, flags), + struct task_struct *p, unsigned int flags) + +DEFINE_CLASS_IS_UNCONDITIONAL(sched_change) =20 #include "ext.h" =20 --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -64,7 +64,6 @@ static int effective_prio(struct task_st =20 void set_user_nice(struct task_struct *p, long nice) { - bool queued, running; struct rq *rq; int old_prio; =20 @@ -90,22 +89,12 @@ void set_user_nice(struct task_struct *p return; } =20 - queued =3D task_on_rq_queued(p); - running =3D task_current_donor(rq, p); - if (queued) - dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); - if (running) - put_prev_task(rq, p); - - p->static_prio =3D NICE_TO_PRIO(nice); - set_load_weight(p, true); - old_prio =3D p->prio; - p->prio =3D effective_prio(p); - - if (queued) - enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - if (running) - set_next_task(rq, p); + scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK) { + p->static_prio =3D NICE_TO_PRIO(nice); + set_load_weight(p, true); + old_prio =3D p->prio; + p->prio =3D effective_prio(p); + } =20 /* * If the task increased its priority or is running and @@ -515,7 +504,7 @@ int __sched_setscheduler(struct task_str bool user, bool pi) { int oldpolicy =3D -1, policy =3D attr->sched_policy; - int retval, oldprio, newprio, queued, running; + int retval, oldprio, newprio; const struct sched_class *prev_class, *next_class; struct balance_callback *head; struct rq_flags rf; @@ -698,33 +687,25 @@ int __sched_setscheduler(struct task_str if (prev_class !=3D next_class && p->se.sched_delayed) dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK); =20 - queued =3D task_on_rq_queued(p); - running =3D task_current_donor(rq, p); - if (queued) - dequeue_task(rq, p, queue_flags); - if (running) - put_prev_task(rq, p); - - if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) { - __setscheduler_params(p, attr); - p->sched_class =3D next_class; - p->prio =3D newprio; - } - __setscheduler_uclamp(p, attr); - check_class_changing(rq, p, prev_class); + scoped_guard (sched_change, p, queue_flags) { =20 - if (queued) { - /* - * We enqueue to tail when the priority of a task is - * increased (user space view). - */ - if (oldprio < p->prio) - queue_flags |=3D ENQUEUE_HEAD; + if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) { + __setscheduler_params(p, attr); + p->sched_class =3D next_class; + p->prio =3D newprio; + } + __setscheduler_uclamp(p, attr); + check_class_changing(rq, p, prev_class); =20 - enqueue_task(rq, p, queue_flags); + if (scope->queued) { + /* + * We enqueue to tail when the priority of a task is + * increased (user space view). + */ + if (oldprio < p->prio) + scope->flags |=3D ENQUEUE_HEAD; + } } - if (running) - set_next_task(rq, p); =20 check_class_changed(rq, p, prev_class, oldprio);