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Date: Fri, 22 May 2026 13:30:54 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: John Stultz <jstultz@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Joel Fernandes <joelagnelf@nvidia.com>,
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Subject: Re: [PATCH v29 5/9] sched: Have try_to_wake_up() handle
 return-migration for PROXY_WAKING case
Message-ID: <20260522113054.GO3126523@noisy.programming.kicks-ass.net>
References: <20260512025635.2840817-1-jstultz@google.com>
 <20260512025635.2840817-6-jstultz@google.com>
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In-Reply-To: <20260512025635.2840817-6-jstultz@google.com>

On Tue, May 12, 2026 at 02:56:15AM +0000, John Stultz wrote:

>  migrate_task:
>  	proxy_migrate_task(rq, rf, p, owner_cpu);
> @@ -7107,6 +7101,9 @@ static void __sched notrace __schedule(int sched_mode)
>  	if (sched_proxy_exec()) {
>  		struct task_struct *prev_donor = rq->donor;
>  
> +		if (!prev_state && prev->blocked_on)
> +			clear_task_blocked_on(prev, NULL);
> +
>  		rq_set_donor(rq, next);
>  		if (unlikely(next->blocked_on)) {
>  			next = find_proxy_task(rq, next, &rf);

This adds a @prev dereference, after you've just explained how we should
not use @prev after a lock break.