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Date: Tue, 19 May 2026 16:46:23 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: John Stultz <jstultz@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Juri Lelli <juri.lelli@redhat.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Connor O'Brien <connoro@google.com>,
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	kuyo chang <kuyo.chang@mediatek.com>, hupu <hupu.gm@gmail.com>,
	kernel-team@android.com
Subject: Re: [PATCH v29 7/9] sched: Add blocked_donor link to task for
 smarter mutex handoffs
Message-ID: <20260519144623.GA3493195@noisy.programming.kicks-ass.net>
References: <20260512025635.2840817-1-jstultz@google.com>
 <20260512025635.2840817-8-jstultz@google.com>
 <20260519143238.GB2934902@noisy.programming.kicks-ass.net>
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In-Reply-To: <20260519143238.GB2934902@noisy.programming.kicks-ass.net>

On Tue, May 19, 2026 at 04:32:38PM +0200, Peter Zijlstra wrote:

> Notably, blocked_donor is a back link that is specific to the current
> schedule() call / donor pick cycle.
> 
> This means it is stable when either: holding rq->lock or disabling
> preemption -- because when preemption is disabled.

... you cannot schedule().