Re: [PATCH v2] sched_ext: Clarify CPU context for running/stopping callbacks

[Tejun Heo <tj@kernel.org>]

On Wed, Apr 23, 2025 at 11:02:05PM +0200, Andrea Righi wrote:
> The ops.running() and ops.stopping() callbacks can be invoked from a CPU
> other than the one the task is assigned to, particularly when a task
> property is changed, as both scx_next_task_scx() and dequeue_task_scx() may
> run on CPUs different from the task's target CPU.
> 
> This behavior can lead to confusion or incorrect assumptions if not
> properly clarified, potentially resulting in bugs (see [1]).
> 
> Therefore, update the documentation to clarify this aspect and advise
> users to use scx_bpf_task_cpu() to determine the actual CPU the task
> will run on or was running on.
> 
> [1] https://github.com/sched-ext/scx/pull/1728
> 
> Cc: Jake Hillion <jake@hillion.co.uk>
> Cc: Changwoo Min <changwoo@igalia.com>
> Signed-off-by: Andrea Righi <arighi@nvidia.com>

Applied to sched_ext/for-6.16.

Thanks.

-- 
tejun