linux-kernel - Re: [PATCHSET RESEND v2 sched_ext/for-6.19] sched_ext: Fix SCX_KICK

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Message-ID: <aPlKCzr8i0Ggow1O@gpd4>
Date: Wed, 22 Oct 2025 23:18:03 +0200
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>
Cc: void@...ifault.com, changwoo@...lia.com, linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev, peterz@...radead.org
Subject: Re: [PATCHSET RESEND v2 sched_ext/for-6.19] sched_ext: Fix
 SCX_KICK_WAIT reliability

Hi Tejun,

On Wed, Oct 22, 2025 at 10:56:26AM -1000, Tejun Heo wrote:
> Resending because the original v2 posting didn't include the full recipient
> list on the individual patches due to git send-email invocation error. Sorry
> about the noise.
> 
> SCX_KICK_WAIT is used to synchronously wait for the target CPU to complete
> a reschedule and can be used to implement operations like core scheduling.
> However, recent scheduler refactorings broke its reliability. This series
> fixes the issue and improves the code clarity.
> 
> v2: - In patch #2, also increment pnt_seq in pick_task_scx() to handle
>       same-task re-selection (Andrea Righi).
>     - In patch #2, use smp_cond_load_acquire() for the busy-wait loop for
>       better architecture optimization (Peter Zijlstra).
>     - Added patch #3 to rename pnt_seq to kick_sync for clarity.
> 
> v1: http://lkml.kernel.org/r/20251021210354.89570-1-tj@kernel.org

Looks good to me!

Reviewed-by: Andrea Righi <arighi@...dia.com>

Thanks,
-Andrea

> 
> Based on sched_ext/for-6.19 (2dbbdeda77a6).
> 
>  1 sched_ext: Don't kick CPUs running higher classes
>  2 sched_ext: Fix SCX_KICK_WAIT to work reliably
>  3 sched_ext: Rename pnt_seq to kick_sync
> 
> Git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-fix-kick_wait
> 
>  kernel/sched/ext.c          | 129 ++++++++++++++++++++++++--------------------
>  kernel/sched/ext_internal.h |   6 ++-
>  kernel/sched/sched.h        |   2 +-
>  3 files changed, 75 insertions(+), 62 deletions(-)
> 
> --
> tejun