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From: "Michal Koutný" <mkoutny@suse.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Sultan Alsawaf <sultan@kerneltoast.com>,
	Anton Vorontsov <anton@enomsg.org>,
	Ben Segall <bsegall@google.com>, Colin Cross <ccross@android.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	dri-devel@lists.freedesktop.org, Ingo Molnar <mingo@redhat.com>,
	John Ogness <john.ogness@linutronix.de>,
	Juri Lelli <juri.lelli@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>, Mel Gorman <mgorman@suse.de>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Tony Luck <tony.luck@intel.com>
Subject: Re: printk deadlock due to double lock attempt on current CPU's runqueue
Date: Wed, 10 Nov 2021 11:45:10 +0100	[thread overview]
Message-ID: <20211110104510.GB20566@blackbody.suse.cz> (raw)
In-Reply-To: <CAKfTPtC_A-_sfQ+rm440oHwd2gUZ222FMwsi-JTkyLPc-x0qrw@mail.gmail.com>

On Wed, Nov 10, 2021 at 10:00:35AM +0100, Vincent Guittot <vincent.guittot@linaro.org> wrote:
> Is it the same SCHED_WARN_ON(rq->tmp_alone_branch !=
> &rq->leaf_cfs_rq_list); that generates the deadlock on v5.15 too ?
> 
> one remaining tmp_alone_branch warning has been fixed in v5.15 with
> 2630cde26711 ("sched/fair: Add ancestors of unthrottled undecayed cfs_rq")

AFAIK, the warning is typically triggered on v5.13 when CPU throttling is
employeed. The cfs_rq list is mis-ordered but it shouldn't be fatal.
But the throttling currently (since v5.13 too) also exposes a race on
task_group removal that can lead to corrupting the cfs_rq list (another
thread [1], I'll leave this thread for printk (non)-locking).

HTH,
Michal

[1] https://lore.kernel.org/r/20211011172236.11223-1-mkoutny@suse.com/

  reply	other threads:[~2021-11-10 10:45 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-09 20:06 printk deadlock due to double lock attempt on current CPU's runqueue Sultan Alsawaf
2021-11-09 21:38 ` Peter Zijlstra
2021-11-10  9:00   ` Vincent Guittot
2021-11-10 10:45     ` Michal Koutný [this message]
2021-11-10 19:50     ` Sultan Alsawaf
2021-11-12  7:50       ` Vincent Guittot
2021-11-10  9:37   ` Daniel Vetter
2021-11-10 10:07     ` John Ogness
2021-11-10 10:44       ` Daniel Vetter
2021-11-10 20:03       ` Sultan Alsawaf
2021-11-11  8:28         ` John Ogness
2021-11-11  9:27     ` Petr Mladek
2021-11-10 10:50 ` Petr Mladek
2021-11-10 11:20   ` Peter Zijlstra
2021-11-10 13:21     ` Daniel Vetter

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