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Date:   Tue, 12 Sep 2023 13:26:43 +0200
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     linux-kernel@vger.kernel.org, tglx@linutronix.de,
        boqun.feng@gmail.com, bristot@redhat.com, bsegall@google.com,
        dietmar.eggemann@arm.com, jstultz@google.com,
        juri.lelli@redhat.com, longman@redhat.com, mgorman@suse.de,
        mingo@redhat.com, rostedt@goodmis.org, swood@redhat.com,
        vincent.guittot@linaro.org, vschneid@redhat.com, will@kernel.org
Subject: Re: [PATCH v3 7/7] locking/rtmutex: Acquire the hb lock via trylock
 after wait-proxylock.
Message-ID: <20230912112643.R4IrwXEB@linutronix.de>
References: <20230908162254.999499-1-bigeasy@linutronix.de>
 <20230908162254.999499-8-bigeasy@linutronix.de>
 <20230911141135.GB9098@noisy.programming.kicks-ass.net>
 <20230912105745.GB13926@noisy.programming.kicks-ass.net>
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On 2023-09-12 12:57:45 [+0200], Peter Zijlstra wrote:
> > --- a/kernel/futex/pi.c
> > +++ b/kernel/futex/pi.c
> > @@ -1147,19 +1143,34 @@ int futex_unlock_pi(u32 __user *uaddr, unsigned=
 int flags)
=E2=80=A6
> > +		rt_waiter =3D rt_mutex_top_waiter(&pi_state->pi_mutex);
> > +		if (!rt_waiter)
> > +			goto do_uncontended;
>=20
> That ^ needs to drop wait_lock before the goto.

Ach, you noticed that one. Wrote a reply a few minutes after that one.

Sebastian