Re: [PATCH v23 2/9] sched: Fix modifying donor->blocked on without proper locking

[K Prateek Nayak]

Hello John,

On 10/30/2025 5:48 AM, John Stultz wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 517b26c515bc5..0533a14ce5935 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6591,7 +6591,7 @@ static struct task_struct *proxy_deactivate(struct rq *rq, struct task_struct *d
>  		 * as unblocked, as we aren't doing proxy-migrations
>  		 * yet (more logic will be needed then).
>  		 */
> -		donor->blocked_on = NULL;
> +		clear_task_blocked_on(donor, NULL);

nit. You can probably switch this to use __clear_task_blocked_on() in
the previous patch and then to the clear_task_blocked_on() variant here.
It makes it more clear that proxy_deactivate() is now out of the
"donor->blocked_lock" critical section.

Either way, no strong feelings.

>  	}
>  	return NULL;
>  }
> @@ -6619,6 +6619,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
>  	int this_cpu = cpu_of(rq);
>  	struct task_struct *p;
>  	struct mutex *mutex;
> +	enum { FOUND, DEACTIVATE_DONOR } action = FOUND;

nit. If you move that declaration to the top, you can preserve the nice
reverse xmas arrangement ;)

Apart from those couple of nits, feel free to include:

Reviewed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>

-- 
Thanks and Regards,
Prateek