linux-kernel - Re: [PATCH v11 1/7] locking/mutex: Remove wakeups from under mutex::wait

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Message-ID: <20240712145247.GL27299@noisy.programming.kicks-ass.net>
Date: Fri, 12 Jul 2024 16:52:47 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: John Stultz <jstultz@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Joel Fernandes <joelaf@...gle.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>,
	Youssef Esmat <youssefesmat@...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>, kernel-team@...roid.com,
	Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH v11 1/7] locking/mutex: Remove wakeups from under
 mutex::wait_lock

On Tue, Jul 09, 2024 at 01:31:44PM -0700, John Stultz wrote:
> @@ -405,8 +409,10 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
>  	 * die or wound us.
>  	 */
>  	lock_wait_lock(&lock->base);
> -	__ww_mutex_check_waiters(&lock->base, ctx);
> +	__ww_mutex_check_waiters(&lock->base, ctx, &wake_q);

  preempt_disable()

>  	unlock_wait_lock(&lock->base);
> +
> +	wake_up_q(&wake_q);

  preempt_enable();

>  }
>  
>  static __always_inline int