Re: [PATCH 01/12] sched/core: Skip migration disabled tasks in proxy execution

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Jul 02, 2026 at 07:09:17PM +0200, Andrea Righi wrote:
> Never attempt to migrate migration-disabled tasks or tasks that can only
> run on a single CPU when switching donor's execution context, preventing
> task pinning violations.
> 
> Signed-off-by: Andrea Righi <arighi@nvidia.com>
> ---
>  kernel/sched/core.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3cc6fb1d20547..8a3eecc7caf5d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6936,6 +6936,20 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
>  			 */
>  			if (curr_in_chain)
>  				return proxy_resched_idle(rq);
> +			/*
> +			 * Tasks pinned to a single CPU (per-CPU kthreads via
> +			 * kthread_bind(), tasks under migrate_disable()) cannot
> +			 * be moved to @owner_cpu. proxy_migrate_task() uses
> +			 * __set_task_cpu() which would silently violate the
> +			 * pinning and leave the task to run on a CPU outside
> +			 * its cpus_ptr once it is unblocked. Deactivate it on
> +			 * this CPU; the owner running elsewhere will wake @p
> +			 * back up when the mutex becomes available.
> +			 */

No, this is actually OK. Remember, we only migrate the scheduling
context, but the task as such won't ever execute on the remote CPU.