Re: [PATCH v26 05/10] sched: Fix modifying donor->blocked on without proper locking

[Steven Rostedt]

Nit, Subject needs s/donor->blocked on/donor->blocked_on/

On Tue, 24 Mar 2026 19:13:20 +0000
John Stultz <jstultz@xxxxxxxxxx> wrote:

> @@ -6595,6 +6595,7 @@ static struct task_struct *proxy_deactivate(struct rq *rq, struct task_struct *d
>  static struct task_struct *
>  find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
>  {
> +	enum { FOUND, DEACTIVATE_DONOR } action = FOUND;
>  	struct task_struct *owner = NULL;
>  	int this_cpu = cpu_of(rq);
>  	struct task_struct *p;
> @@ -6628,12 +6629,14 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
>  
>  		if (!READ_ONCE(owner->on_rq) || owner->se.sched_delayed) {
>  			/* XXX Don't handle blocked owners/delayed dequeue yet */
> -			return proxy_deactivate(rq, donor);
> +			action = DEACTIVATE_DONOR;
> +			break;
>  		}
>  
>  		if (task_cpu(owner) != this_cpu) {
>  			/* XXX Don't handle migrations yet */
> -			return proxy_deactivate(rq, donor);
> +			action = DEACTIVATE_DONOR;
> +			break;
>  		}
>  
>  		if (task_on_rq_migrating(owner)) {
> @@ -6691,6 +6694,13 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
>  		 */
>  	}
>  
> +	/* Handle actions we need to do outside of the guard() scope */
> +	switch (action) {
> +	case DEACTIVATE_DONOR:
> +		return proxy_deactivate(rq, donor);
> +	case FOUND:
> +		/* fallthrough */;

A fall through comment for exiting the switch statement is rather
confusing. Fallthrough usually means to fall into the next case statement.
You could just do:

	switch (action) {
	case DEACTIVATE_DONOR:
		return proxy_deactivate(rq, donor);
	case FOUND:
		break;
	}

Which is what I believe is the normal method of adding enums to switch
statements that don't do anything.

-- Steve



> +	}
>  	WARN_ON_ONCE(owner && !owner->on_rq);
>  	return owner;
>  }