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Message-ID: <176060720464.709179.18344719544175290384.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:33:24 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: K Prateek Nayak <kprateek.nayak@....com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>, Tejun Heo <tj@...nel.org>,
Vincent Guittot <vincent.guittot@...aro.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Cleanup the sched_change NOCLOCK usage
The following commit has been merged into the sched/core branch of tip:
Commit-ID: d4c64207b88a60dd15a38c790bb73c0b6f9a8c40
Gitweb: https://git.kernel.org/tip/d4c64207b88a60dd15a38c790bb73c0b6f9a8c40
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 11 Sep 2025 12:09:19 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 16 Oct 2025 11:13:54 +02:00
sched: Cleanup the sched_change NOCLOCK usage
Teach the sched_change pattern how to do update_rq_clock(); this
allows for some simplifications / cleanups.
Suggested-by: K Prateek Nayak <kprateek.nayak@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Juri Lelli <juri.lelli@...hat.com>
Acked-by: Tejun Heo <tj@...nel.org>
Acked-by: Vincent Guittot <vincent.guittot@...aro.org>
---
kernel/sched/core.c | 33 +++++++++++----------------------
kernel/sched/ext.c | 4 +---
kernel/sched/syscalls.c | 8 ++------
3 files changed, 14 insertions(+), 31 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e715147..3d5659f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2346,10 +2346,8 @@ static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
if (p->cpus_ptr != &p->cpus_mask)
return;
- scoped_guard (task_rq_lock, p) {
- update_rq_clock(scope.rq);
+ scoped_guard (task_rq_lock, p)
do_set_cpus_allowed(p, &ac);
- }
}
void ___migrate_enable(void)
@@ -2666,9 +2664,7 @@ void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx
static void
do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
{
- u32 flags = DEQUEUE_SAVE | DEQUEUE_NOCLOCK;
-
- scoped_guard (sched_change, p, flags) {
+ scoped_guard (sched_change, p, DEQUEUE_SAVE) {
p->sched_class->set_cpus_allowed(p, ctx);
mm_set_cpus_allowed(p->mm, ctx->new_mask);
}
@@ -2690,10 +2686,8 @@ void set_cpus_allowed_force(struct task_struct *p, const struct cpumask *new_mas
struct rcu_head rcu;
};
- scoped_guard (__task_rq_lock, p) {
- update_rq_clock(scope.rq);
+ scoped_guard (__task_rq_lock, p)
do_set_cpus_allowed(p, &ac);
- }
/*
* Because this is called with p->pi_lock held, it is not possible
@@ -9108,16 +9102,13 @@ static void sched_change_group(struct task_struct *tsk)
*/
void sched_move_task(struct task_struct *tsk, bool for_autogroup)
{
- unsigned int queue_flags =
- DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
bool resched = false;
struct rq *rq;
CLASS(task_rq_lock, rq_guard)(tsk);
rq = rq_guard.rq;
- update_rq_clock(rq);
-
scoped_guard (sched_change, tsk, queue_flags) {
sched_change_group(tsk);
if (!for_autogroup)
@@ -10792,16 +10783,14 @@ struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigned int
lockdep_assert_rq_held(rq);
+ if (!(flags & DEQUEUE_NOCLOCK)) {
+ update_rq_clock(rq);
+ flags |= DEQUEUE_NOCLOCK;
+ }
+
if (flags & DEQUEUE_CLASS) {
- if (p->sched_class->switching_from) {
- /*
- * switching_from_fair() assumes CLASS implies NOCLOCK;
- * fixing this assumption would mean switching_from()
- * would need to be able to change flags.
- */
- WARN_ON(!(flags & DEQUEUE_NOCLOCK));
+ if (p->sched_class->switching_from)
p->sched_class->switching_from(rq, p);
- }
}
*ctx = (struct sched_change_ctx){
@@ -10840,7 +10829,7 @@ void sched_change_end(struct sched_change_ctx *ctx)
p->sched_class->switching_to(rq, p);
if (ctx->queued)
- enqueue_task(rq, p, ctx->flags | ENQUEUE_NOCLOCK);
+ enqueue_task(rq, p, ctx->flags);
if (ctx->running)
set_next_task(rq, p);
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index ad371b6..5717042 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4654,7 +4654,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
percpu_down_write(&scx_fork_rwsem);
scx_task_iter_start(&sti);
while ((p = scx_task_iter_next_locked(&sti))) {
- unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
const struct sched_class *old_class = p->sched_class;
const struct sched_class *new_class =
__setscheduler_class(p->policy, p->prio);
@@ -4662,8 +4662,6 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
if (!tryget_task_struct(p))
continue;
- update_rq_clock(task_rq(p));
-
if (old_class != new_class)
queue_flags |= DEQUEUE_CLASS;
diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c
index 20af564..8f0f603 100644
--- a/kernel/sched/syscalls.c
+++ b/kernel/sched/syscalls.c
@@ -64,7 +64,6 @@ static int effective_prio(struct task_struct *p)
void set_user_nice(struct task_struct *p, long nice)
{
- struct rq *rq;
int old_prio;
if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
@@ -73,10 +72,7 @@ void set_user_nice(struct task_struct *p, long nice)
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
- CLASS(task_rq_lock, rq_guard)(p);
- rq = rq_guard.rq;
-
- update_rq_clock(rq);
+ guard(task_rq_lock)(p);
/*
* The RT priorities are set via sched_setscheduler(), but we still
@@ -89,7 +85,7 @@ void set_user_nice(struct task_struct *p, long nice)
return;
}
- scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK) {
+ scoped_guard (sched_change, p, DEQUEUE_SAVE) {
p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p, true);
old_prio = p->prio;
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