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Date: Wed, 22 Apr 2026 15:45:19 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Boqun Feng <boqun@kernel.org>, Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Waiman Long <longman@redhat.com>, John Stultz <jstultz@google.com>,
	=?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux regressions mailing list <regressions@lists.linux.dev>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION] sched/core merge 1c3b68f0d55b: futex_waitv lost
 wakeup hangs RE Engine games and PID 1 init
Message-ID: <20260422134519.GQ3102624@noisy.programming.kicks-ass.net>
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 <20260421144105.GA3179637@noisy.programming.kicks-ass.net>
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On Wed, Apr 22, 2026 at 03:48:16PM +0500, Mikhail Gavrilov wrote:
> On Tue, Apr 21, 2026 at 7:41 PM Peter Zijlstra <peterz@infradead.org> wrote:>
> > Specifically, see this thread:
> >
> >   https://lore.kernel.org/r/95651a71-1adf-45ba-83eb-5744bc6d4a52@amd.com
> 
> You're right — it is to blame, and I was about to follow up to say so.
> 
> After sending the first mail I kept re-verifying markers with the
> stricter RE2+RE9 workload and found that 33c66eb5e984 (parent 1 of
> 1c3b68f0, which I had marked "good") actually reproduces the hang too.
> A third bisect run with the stricter workload converges unambiguously
> on:
> 
>   25500ba7e77c ("locking/mutex: Remove the list_head from struct mutex")
> 
> Parent b9bdd4b68404 ("locking/semaphore: Remove the list_head from struct
> semaphore"): good. 25500ba7e77c: bad.

Please test this:

  https://lore.kernel.org/r/20260422092335.GH3102924@noisy.programming.kicks-ass.net

and reply there with your findings if possible.