From nobody Mon Nov 25 04:45:10 2024 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 0A56A213EE0 for ; Wed, 30 Oct 2024 15:25:53 +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=1730301956; cv=none; b=X4/uznqFi1Cn6OLaMH4zZriNykXB6jjjgb8JgZAlRaIMJFbZyhvRGPy/JvMlL9n0ojV/mC8eIFLlW6VBAdLIahzTcctzkkCD3QzH5QAgmMieeGzjITANcpvumI4pcOzv/abdX8I11/uIawwtymI71AGmtLDvsCK6ECU6MytMdvM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730301956; c=relaxed/simple; bh=RNOg5ouTL1U+ujWCIwyxrXtmr4rRrvxV8iy7MoAAMzw=; h=Message-Id:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=Pc/O5okPLlB4UZ6c+7N9fnoK28M43cUCYuOlhpJstnaI6Fq0IyZN7ZHM4ALLr2wK5yM8LXKWpudR0TuXHPhe0FFosv2nsG1NF5S8FMQGKFx8gr8b4theRN3yxvAzMYBMHJ6P4oFnWJBzqsenaAMTSjSx79PBQzPVO3axowDzIXo= 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=bp1GsDCF; 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="bp1GsDCF" 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=aunwiDDKYmVRvfITOprvRJLMm2ei70V4JyWWDCQb24U=; b=bp1GsDCF9nZj4N+lWP9O1kDt1e oyzl/jBSZua0slb1ZAQVsO1EON6kbRZgkAl30MGsO7i3ht+68pcO7aaOfCNqpRT8LiLRoQJ2Xs73G pmgdJ7vSVXqs83/S6azQtsTtUdnS3Q9vi6GpmPaezX+C3aouZZ2EcvBcxKlueg6PgsIP9I/vOPKLK ND/M4mdD922hXabXWHjSsBl9hcqXUNkWSTQrzXhZ8mwHKlp0QEhNbhwJZf26ccxa8Hlsv/2nDEeqw b1C5OUqRuPEFJY2sZJmJOLqgM9WDvoBpyOouiKJlIiFW0F0ewA5didolsX86Ls0IvKXbkx27Tu+vJ 6JnfUE5Q==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1t6AZs-0000000AI28-3P1D; Wed, 30 Oct 2024 15:25:45 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id E9D84301D03; Wed, 30 Oct 2024 16:25:43 +0100 (CET) Message-Id: <20241030152142.711768679@infradead.org> User-Agent: quilt/0.65 Date: Wed, 30 Oct 2024 16:12:59 +0100 From: Peter Zijlstra To: mingo@kernel.org Cc: peterz@infradead.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, tj@kernel.org, void@manifault.com, linux-kernel@vger.kernel.org Subject: [RFC][PATCH 4/6] sched: Fold sched_class::switch{ing,ed}_{to,from}() into the change pattern References: <20241030151255.300069509@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" Add {DE,EN}QUEUE_CLASS and fold the sched_class::switch* methods into the change pattern. This completes and makes the pattern more symmetric. This changes the order of callbacks slightly: | | switching_from() dequeue_task(); | dequeue_task() put_prev_task(); | put_prev_task() | switched_from() | ... change task ... | ... change task ... | switching_to(); | switching_to() enqueue_task(); | enqueue_task() set_next_task(); | set_next_task() prev_class->switched_from() | switched_to() | switched_to() | Notably, it moves the switched_from() callback right after the dequeue/put. Existing implementations don't appear to be affected by this change in location -- specifically the task isn't enqueued on the class in question in either location. Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/core.c | 61 ++++++++++++++++++++----------------------= ----- kernel/sched/ext.c | 19 ++++++++++---- kernel/sched/idle.c | 4 +-- kernel/sched/rt.c | 4 +-- kernel/sched/sched.h | 21 ++++++---------- kernel/sched/stop_task.c | 4 +-- kernel/sched/syscalls.c | 7 +++-- 7 files changed, 59 insertions(+), 61 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2102,34 +2102,9 @@ inline int task_curr(const struct task_s return cpu_curr(task_cpu(p)) =3D=3D p; } =20 -/* - * ->switching_to() is called with the pi_lock and rq_lock held and must n= ot - * mess with locking. - */ -void check_class_changing(struct rq *rq, struct task_struct *p, - const struct sched_class *prev_class) +void check_prio_changed(struct rq *rq, struct task_struct *p, int oldprio) { - if (prev_class !=3D p->sched_class && p->sched_class->switching_to) - p->sched_class->switching_to(rq, p); -} - -/* - * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, - * use the balance_callback list if you want balancing. - * - * this means any call to check_class_changed() must be followed by a call= to - * balance_callback(). - */ -void check_class_changed(struct rq *rq, struct task_struct *p, - const struct sched_class *prev_class, - int oldprio) -{ - if (prev_class !=3D p->sched_class) { - if (prev_class->switched_from) - prev_class->switched_from(rq, p); - - p->sched_class->switched_to(rq, p); - } else if (oldprio !=3D p->prio || dl_task(p)) + if (oldprio !=3D p->prio || dl_task(p)) p->sched_class->prio_changed(rq, p, oldprio); } =20 @@ -7161,6 +7136,9 @@ void rt_mutex_setprio(struct task_struct prev_class =3D p->sched_class; next_class =3D __setscheduler_class(p->policy, prio); =20 + if (prev_class !=3D next_class) + queue_flag |=3D DEQUEUE_CLASS; + if (prev_class !=3D next_class && p->se.sched_delayed) dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK); =20 @@ -7197,11 +7175,10 @@ void rt_mutex_setprio(struct task_struct =20 p->sched_class =3D next_class; p->prio =3D prio; - - check_class_changing(rq, p, prev_class); } =20 - check_class_changed(rq, p, prev_class, oldprio); + if (!(queue_flag & DEQUEUE_CLASS)) + check_prio_changed(rq, p, oldprio); out_unlock: /* Avoid rq from going away on us: */ preempt_disable(); @@ -10550,6 +10527,12 @@ void sched_mm_cid_fork(struct task_struc struct sched_change_ctx sched_change_begin(struct task_struct *p, unsigned= int flags) { struct rq *rq =3D task_rq(p); + + lockdep_assert_rq_held(rq); + + if ((flags & DEQUEUE_CLASS) && p->sched_class->switching_from) + p->sched_class->switching_from(rq, p); + struct sched_change_ctx ctx =3D { .p =3D p, .flags =3D flags, @@ -10557,24 +10540,32 @@ struct sched_change_ctx sched_change_beg .running =3D task_current(rq, p), }; =20 - lockdep_assert_rq_held(rq); - if (ctx.queued) dequeue_task(rq, p, flags); if (ctx.running) put_prev_task(rq, p); =20 + if ((flags & DEQUEUE_CLASS) && p->sched_class->switched_from) + p->sched_class->switched_from(rq, p); + return ctx; } =20 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.flags & ENQUEUE_CLASS) && p->sched_class->switching_to) + p->sched_class->switching_to(rq, p); + if (ctx.queued) - enqueue_task(rq, ctx.p, ctx.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); + + if ((ctx.flags & ENQUEUE_CLASS) && p->sched_class->switched_to) + p->sched_class->switched_to(rq, p); } --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4487,19 +4487,24 @@ static void scx_ops_disable_workfn(struc =20 scx_task_iter_start(&sti); while ((p =3D scx_task_iter_next_locked(&sti))) { + unsigned int queue_flags =3D DEQUEUE_SAVE | DEQUEUE_MOVE; const struct sched_class *old_class =3D p->sched_class; const struct sched_class *new_class =3D __setscheduler_class(p->policy, p->prio); =20 + if (old_class !=3D new_class) + queue_flags |=3D DEQUEUE_CLASS; + if (old_class !=3D new_class && p->se.sched_delayed) dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); =20 - scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE) { + scoped_guard (sched_change, p, queue_flags) { 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); + if (!(queue_flags & DEQUEUE_CLASS)) + check_prio_changed(task_rq(p), p, p->prio); + scx_ops_exit_task(p); } scx_task_iter_stop(&sti); @@ -5199,20 +5204,24 @@ static int scx_ops_enable(struct sched_e percpu_down_write(&scx_fork_rwsem); scx_task_iter_start(&sti); while ((p =3D scx_task_iter_next_locked(&sti))) { + unsigned int queue_flags =3D DEQUEUE_SAVE | DEQUEUE_MOVE; const struct sched_class *old_class =3D p->sched_class; const struct sched_class *new_class =3D __setscheduler_class(p->policy, p->prio); =20 + if (old_class !=3D new_class) + queue_flags |=3D DEQUEUE_CLASS; + if (old_class !=3D new_class && p->se.sched_delayed) dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); =20 scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE) { 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); + if (!(queue_flags & DEQUEUE_CLASS)) + check_prio_changed(task_rq(p), p, p->prio); } scx_task_iter_stop(&sti); percpu_up_write(&scx_fork_rwsem); --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -494,7 +494,7 @@ static void task_tick_idle(struct rq *rq { } =20 -static void switched_to_idle(struct rq *rq, struct task_struct *p) +static void switching_to_idle(struct rq *rq, struct task_struct *p) { BUG(); } @@ -534,6 +534,6 @@ DEFINE_SCHED_CLASS(idle) =3D { .task_tick =3D task_tick_idle, =20 .prio_changed =3D prio_changed_idle, - .switched_to =3D switched_to_idle, + .switched_to =3D switching_to_idle, .update_curr =3D update_curr_idle, }; --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2633,7 +2633,6 @@ DEFINE_SCHED_CLASS(rt) =3D { .rq_online =3D rq_online_rt, .rq_offline =3D rq_offline_rt, .task_woken =3D task_woken_rt, - .switched_from =3D switched_from_rt, .find_lock_rq =3D find_lock_lowest_rq, #endif =20 @@ -2641,8 +2640,9 @@ DEFINE_SCHED_CLASS(rt) =3D { =20 .get_rr_interval =3D get_rr_interval_rt, =20 - .prio_changed =3D prio_changed_rt, + .switched_from =3D switched_from_rt, .switched_to =3D switched_to_rt, + .prio_changed =3D prio_changed_rt, =20 .update_curr =3D update_curr_rt, =20 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2340,6 +2340,7 @@ extern const u32 sched_prio_to_wmult[40 =20 #define DEQUEUE_MIGRATING 0x10 /* Matches ENQUEUE_MIGRATING */ #define DEQUEUE_DELAYED 0x20 /* Matches ENQUEUE_DELAYED */ +#define DEQUEUE_CLASS 0x40 /* Matches ENQUEUE_CLASS */ =20 #define DEQUEUE_SPECIAL 0x0100 =20 @@ -2350,6 +2351,7 @@ extern const u32 sched_prio_to_wmult[40 =20 #define ENQUEUE_MIGRATING 0x10 #define ENQUEUE_DELAYED 0x20 +#define ENQUEUE_CLASS 0x40 =20 #define ENQUEUE_HEAD 0x0100 #define ENQUEUE_REPLENISH 0x0200 @@ -2415,14 +2417,11 @@ struct sched_class { void (*task_fork)(struct task_struct *p); void (*task_dead)(struct task_struct *p); =20 - /* - * The switched_from() call is allowed to drop rq->lock, therefore we - * cannot assume the switched_from/switched_to pair is serialized by - * rq->lock. They are however serialized by p->pi_lock. - */ - void (*switching_to) (struct rq *this_rq, struct task_struct *task); - void (*switched_from)(struct rq *this_rq, struct task_struct *task); - void (*switched_to) (struct rq *this_rq, struct task_struct *task); + void (*switching_from)(struct rq *this_rq, struct task_struct *task); + void (*switched_from) (struct rq *this_rq, struct task_struct *task); + void (*switching_to) (struct rq *this_rq, struct task_struct *task); + void (*switched_to) (struct rq *this_rq, struct task_struct *task); + void (*reweight_task)(struct rq *this_rq, struct task_struct *task, const struct load_weight *lw); void (*prio_changed) (struct rq *this_rq, struct task_struct *task, @@ -3898,11 +3897,7 @@ extern void set_load_weight(struct task_ extern void enqueue_task(struct rq *rq, struct task_struct *p, int flags); extern bool dequeue_task(struct rq *rq, struct task_struct *p, int flags); =20 -extern void check_class_changing(struct rq *rq, struct task_struct *p, - const struct sched_class *prev_class); -extern void check_class_changed(struct rq *rq, struct task_struct *p, - const struct sched_class *prev_class, - int oldprio); +extern void check_prio_changed(struct rq *rq, struct task_struct *p, int o= ldprio); =20 #ifdef CONFIG_SMP extern struct balance_callback *splice_balance_callbacks(struct rq *rq); --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -76,7 +76,7 @@ static void task_tick_stop(struct rq *rq { } =20 -static void switched_to_stop(struct rq *rq, struct task_struct *p) +static void switching_to_stop(struct rq *rq, struct task_struct *p) { BUG(); /* its impossible to change to this class */ } @@ -115,6 +115,6 @@ DEFINE_SCHED_CLASS(stop) =3D { .task_tick =3D task_tick_stop, =20 .prio_changed =3D prio_changed_stop, - .switched_to =3D switched_to_stop, + .switching_to =3D switching_to_stop, .update_curr =3D update_curr_stop, }; --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -698,6 +698,9 @@ int __sched_setscheduler(struct task_str prev_class =3D p->sched_class; next_class =3D __setscheduler_class(policy, newprio); =20 + if (prev_class !=3D next_class) + queue_flags |=3D DEQUEUE_CLASS; + if (prev_class !=3D next_class && p->se.sched_delayed) dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK); =20 @@ -709,7 +712,6 @@ int __sched_setscheduler(struct task_str p->prio =3D newprio; } __setscheduler_uclamp(p, attr); - check_class_changing(rq, p, prev_class); =20 if (scope.queued) { /* @@ -721,7 +723,8 @@ int __sched_setscheduler(struct task_str } } =20 - check_class_changed(rq, p, prev_class, oldprio); + if (!(queue_flags & DEQUEUE_CLASS)) + check_prio_changed(rq, p, oldprio); =20 /* Avoid rq from going away on us: */ preempt_disable();