From: John Ogness <john.ogness@linutronix.de>
To: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: Daniel Vetter <daniel@ffwll.ch>,
Peter Zijlstra <peterz@infradead.org>,
Anton Vorontsov <anton@enomsg.org>,
Ben Segall <bsegall@google.com>, Colin Cross <ccross@android.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
David Airlie <airlied@linux.ie>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
dri-devel@lists.freedesktop.org, Ingo Molnar <mingo@redhat.com>,
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>,
Vincent Guittot <vincent.guittot@linaro.org>,
mkoutny@suse.com
Subject: Re: printk deadlock due to double lock attempt on current CPU's runqueue
Date: Thu, 11 Nov 2021 09:34:00 +0106 [thread overview]
Message-ID: <87k0hfqepb.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <YYwlnEQO0raDwS86@sultan-box.localdomain>
On 2021-11-10, Sultan Alsawaf <sultan@kerneltoast.com> wrote:
> On Wed, Nov 10, 2021 at 11:13:37AM +0106, John Ogness wrote:
>> Even after we introduce kthread printers, there will still be
>> situations where direct printing is used: booting (before kthreads
>> exist) and shutdown/suspend/crash situations, when the kthreads may
>> not be active.
>
> Although I'm unaware of any ongoing kthread printer work, I'm curious
> to know how a kthread approach wouldn't employ a try_to_wake_up() from
> directly inside printk(), since the try_to_wake_up() hit from inside
> the fbcon code is what caused my deadlock.
The kthread approach triggers irq_work from printk(). The kthread
printer is then woken from the irq_work.
John Ogness
next prev parent reply other threads:[~2021-11-11 8:28 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 [this message]
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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