From: Peter Zijlstra <peterz@infradead.org>
To: John Stultz <jstultz@google.com>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] locking/semaphore: Use wake_q to wake up processes outside lock critical section
Date: Thu, 21 Sep 2023 09:45:38 +0200 [thread overview]
Message-ID: <20230921074538.GD14803@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CANDhNCpsDbz9ZT+h4Zcq-7QMJ-uqs3rW+MXCVcbi2A2hnTjBpQ@mail.gmail.com>
On Wed, Sep 20, 2023 at 05:05:56PM -0700, John Stultz wrote:
> On Fri, Sep 9, 2022 at 12:28 PM Waiman Long <longman@redhat.com> wrote:
> >
> > It was found that a circular lock dependency can happen with the
> > following locking sequence:
> >
> > +--> (console_sem).lock --> &p->pi_lock --> &rq->__lock --+
> > | |
> > +---------------------------------------------------------+
> >
> > The &p->pi_lock --> &rq->__lock sequence is very common in all the
> > task_rq_lock() calls.
>
> Thanks for sending this out! I've been hitting these lockdep warningns
> a lot recently, particularly if I have any debug printks/WARN_ONs in
> the scheduler that trip, so I'm eager to get a fix for this!
https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=debug/experimental
and use with: earlyprintk=serial,ttyS0,115200 force_early_printk, or
somesuch.
I could not have done perf or much of the sched patches without it.
next prev parent reply other threads:[~2023-09-21 20:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 19:28 [PATCH v2] locking/semaphore: Use wake_q to wake up processes outside lock critical section Waiman Long
2022-09-19 19:49 ` Waiman Long
2023-09-21 0:05 ` John Stultz
2023-09-21 0:37 ` Waiman Long
2023-09-21 7:45 ` Peter Zijlstra [this message]
2023-09-21 7:42 ` Peter Zijlstra
2023-09-22 18:45 ` Waiman Long
2023-09-22 19:47 ` Peter Zijlstra
2023-09-23 0:29 ` Waiman Long
-- strict thread matches above, loose matches on Subject: below --
2025-01-22 19:17 Waiman Long
2025-01-26 2:21 ` Waiman Long
2022-02-10 18:10 Waiman Long
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