[PATCH] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

[PATCH] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

[Hao Jia]

From: Hao Jia <jiahao1@lixiang.com>

Since commit d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage"),
update_rq_clock() is called in do_set_cpus_allowed() -> sched_change_begin()
to update the rq clock. This results in a duplicate call update_rq_clock()
in __set_cpus_allowed_ptr_locked().

While holding the rq lock and before calling do_set_cpus_allowed(),
there is nothing that depends on an updated rq_clock.

Therefore, remove the redundant update_rq_clock() in
__set_cpus_allowed_ptr_locked() to avoid the warning about double
rq clock updates.

Fixes: d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage")
Signed-off-by: Hao Jia <jiahao1@lixiang.com>
---
 kernel/sched/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1842285eac1e..1123cd0ddffb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2999,8 +2999,6 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
 	unsigned int dest_cpu;
 	int ret = 0;
 
-	update_rq_clock(rq);
-
 	if (kthread || is_migration_disabled(p)) {
 		/*
 		 * Kernel threads are allowed on online && !active CPUs,
-- 
2.34.1

Re: [PATCH] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

[K Prateek Nayak]

Hello Hao,

On 10/29/2025 3:06 PM, Hao Jia wrote:
> From: Hao Jia <jiahao1@lixiang.com>
> 
> Since commit d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage"),
> update_rq_clock() is called in do_set_cpus_allowed() -> sched_change_begin()
> to update the rq clock. This results in a duplicate call update_rq_clock()
> in __set_cpus_allowed_ptr_locked().
> 
> While holding the rq lock and before calling do_set_cpus_allowed(),
> there is nothing that depends on an updated rq_clock.

I couldn't spot any dependency on rq_clock() until do_set_cpus_allowed()
either so please feel free to include:

Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>

-- 
Thanks and Regards,
Prateek

> 
> Therefore, remove the redundant update_rq_clock() in
> __set_cpus_allowed_ptr_locked() to avoid the warning about double
> rq clock updates.
> 
> Fixes: d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage")
> Signed-off-by: Hao Jia <jiahao1@lixiang.com>
> ---
>  kernel/sched/core.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1842285eac1e..1123cd0ddffb 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2999,8 +2999,6 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
>  	unsigned int dest_cpu;
>  	int ret = 0;
>  
> -	update_rq_clock(rq);
> -
>  	if (kthread || is_migration_disabled(p)) {
>  		/*
>  		 * Kernel threads are allowed on online && !active CPUs,

Re: [PATCH] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

[Peter Zijlstra]

On Thu, Oct 30, 2025 at 09:34:00AM +0530, K Prateek Nayak wrote:
> Hello Hao,
> 
> On 10/29/2025 3:06 PM, Hao Jia wrote:
> > From: Hao Jia <jiahao1@lixiang.com>
> > 
> > Since commit d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage"),
> > update_rq_clock() is called in do_set_cpus_allowed() -> sched_change_begin()
> > to update the rq clock. This results in a duplicate call update_rq_clock()
> > in __set_cpus_allowed_ptr_locked().
> > 
> > While holding the rq lock and before calling do_set_cpus_allowed(),
> > there is nothing that depends on an updated rq_clock.
> 
> I couldn't spot any dependency on rq_clock() until do_set_cpus_allowed()
> either so please feel free to include:
> 
> Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>

Indeed, thanks!

[tip: sched/core] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

[tip-bot2 for Hao Jia]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     e40cea333e60c548e047eaddec6ca48c6632424b
Gitweb:        https://git.kernel.org/tip/e40cea333e60c548e047eaddec6ca48c6632424b
Author:        Hao Jia <jiahao1@lixiang.com>
AuthorDate:    Wed, 29 Oct 2025 17:36:55 +08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 11 Nov 2025 12:33:38 +01:00

sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()

Since commit d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage"),
update_rq_clock() is called in do_set_cpus_allowed() -> sched_change_begin()
to update the rq clock. This results in a duplicate call update_rq_clock()
in __set_cpus_allowed_ptr_locked().

While holding the rq lock and before calling do_set_cpus_allowed(),
there is nothing that depends on an updated rq_clock.

Therefore, remove the redundant update_rq_clock() in
__set_cpus_allowed_ptr_locked() to avoid the warning about double
rq clock updates.

Fixes: d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage")
Signed-off-by: Hao Jia <jiahao1@lixiang.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20251029093655.31252-1-jiahao.kernel@gmail.com
---
 kernel/sched/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 67b5f2f..68f19aa 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2999,8 +2999,6 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
 	unsigned int dest_cpu;
 	int ret = 0;
 
-	update_rq_clock(rq);
-
 	if (kthread || is_migration_disabled(p)) {
 		/*
 		 * Kernel threads are allowed on online && !active CPUs,