linux-kernel - Re: [PATCH v22 2/6] sched/locking: Add blocked_on_state to provide necessary tri-state for proxy return-migration

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Message-ID: <20251009114542.GC4068168@noisy.programming.kicks-ass.net>
Date: Thu, 9 Oct 2025 13:45:42 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: John Stultz <jstultz@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Qais Yousef <qyousef@...alina.io>, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Valentin Schneider <vschneid@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Zimuzo Ezeozue <zezeozue@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Metin Kaya <Metin.Kaya@....com>,
	Xuewen Yan <xuewen.yan94@...il.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Suleiman Souhlal <suleiman@...gle.com>,
	kuyo chang <kuyo.chang@...iatek.com>, hupu <hupu.gm@...il.com>,
	kernel-team@...roid.com
Subject: Re: [PATCH v22 2/6] sched/locking: Add blocked_on_state to provide
 necessary tri-state for proxy return-migration

On Thu, Oct 09, 2025 at 01:43:02PM +0200, Peter Zijlstra wrote:
>  - we should probably have something like:
> 
> 	next = pick_next_task();
> 	rq_set_donor(next)
> 	if (unlikely(task_is_blocked()) {
> 		...
> 	}
> +	WARN_ON_ONCE(next->__state);
> 
>    at all times the task we end up picking should be in RUNNABLE state.

Pfff.. PREEMPT won't like that. Ignore this.