From: Daniel Vetter <daniel@ffwll.ch>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>,
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>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
Tony Luck <tony.luck@intel.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: printk deadlock due to double lock attempt on current CPU's runqueue
Date: Wed, 10 Nov 2021 14:21:31 +0100 [thread overview]
Message-ID: <YYvHW1OpN1L2uInb@phenom.ffwll.local> (raw)
In-Reply-To: <YYuq5d7MYL2wxlOd@hirez.programming.kicks-ass.net>
On Wed, Nov 10, 2021 at 12:20:05PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 10, 2021 at 11:50:38AM +0100, Petr Mladek wrote:
> > On Tue 2021-11-09 12:06:48, Sultan Alsawaf wrote:
> > > Hi,
> > >
> > > I encountered a printk deadlock on 5.13 which appears to still affect the latest
> > > kernel. The deadlock occurs due to printk being used while having the current
> > > CPU's runqueue locked, and the underlying framebuffer console attempting to lock
> > > the same runqueue when printk tries to flush the log buffer.
> > >
> > > I'm not sure what the *correct* solution is here (don't use printk while having
> > > a runqueue locked? don't use schedule_work() from the fbcon path? tell printk
> > > to use one of its lock-less backends?), so I've cc'd all the relevant folks.
> >
> > At the moment, printk_deferred() could be used here. It defers the
> > console handling via irq_work().
>
> I think I've rejected that patch at least twice now :-) John's printk
> stuff will really land real soon now, right.
Yeah whacking all affected prinkt callers just because of fbcon does not
sound like a good idea to me either.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
prev parent reply other threads:[~2021-11-10 13:21 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
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 [this message]
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