Re: [PATCH 04/12] sched_ext: Avoid migrating blocked tasks with proxy execution

[Aiqun(Maria) Yu]

On 7/3/2026 1:09 AM, Andrea Righi wrote:
> From: John Stultz <jstultz@xxxxxxxxxx>
> 
> With proxy execution enabled, mutex blocked tasks stay on the runqueue.
> Later with donor migration they will be migrated when necessary by the
> core scheduler to boost lock owners.
> 
> Don't try to migrate mutex blocked tasks, the proxy logic will handle
> that.
> 
> Co-developed-by: Andrea Righi <arighi@xxxxxxxxxx>
> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>
> Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>

SOB was suggested to have the current committer at the last line.
Not sure if it is the same rule for the subsystem here.

My understanding would be:
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
Co-developed-by: Andrea Righi <arighi@xxxxxxxxxx>
Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>


> ---
>  kernel/sched/ext/ext.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
> index 1588565050679..9a672b9a55f6e 100644
> --- a/kernel/sched/ext/ext.c
> +++ b/kernel/sched/ext/ext.c
> @@ -2150,6 +2150,14 @@ static bool task_can_run_on_remote_rq(struct scx_sched *sch,
>  
>  	WARN_ON_ONCE(task_cpu(p) == cpu);
>  
> +	/* Make sure tasks aren't on a cpu */
> +	if (task_on_cpu(task_rq(p), p))
> +		return false;
> +
> +	/* Don't migrate blocked tasks, proxy-exec will handle this */
> +	if (task_is_blocked(p))
> +		return false;

what about return true here for owner_cpu?
if the owner_cpu is in the move_task_between_dsqs stage for example.

> +
>  	/*
>  	 * If @p has migration disabled, @p->cpus_ptr is updated to contain only
>  	 * the pinned CPU in migrate_disable_switch() while @p is being switched
> @@ -2784,6 +2792,23 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
>  	if (p->scx.flags & SCX_TASK_QUEUED) {
>  		set_task_runnable(rq, p);
>  
> +		/*
> +		 * Mutex-blocked donors stay queued on the runqueue under proxy
> +		 * execution, but the donor never runs as itself, proxy-exec
> +		 * walks the blocked_on chain on the next __schedule() and runs
> +		 * the lock owner in its place.
> +		 *
> +		 * Put the donor on the local DSQ directly, so pick_next_task()
> +		 * can still see it, find_proxy_task() will be invoked on
> +		 * next->blocked_on and either run the chain owner here, or call
> +		 * proxy_force_return() and let BPF make a new dispatch decision
> +		 * once the task is no longer blocked.
> +		 */
> +		if (task_is_blocked(p)) {
> +			dispatch_enqueue(sch, rq, &rq->scx.local_dsq, p, 0);
> +			goto switch_class;
> +		}
> +
>  		/*
>  		 * If @p has slice left and is being put, @p is getting
>  		 * preempted by a higher priority scheduler class or core-sched


-- 
Thx and BRs,
Aiqun(Maria) Yu