From: Peter Zijlstra <peterz@infradead.org>
To: Chengming Zhou <zhouchengming@bytedance.com>
Cc: maarten.lankhorst@linux.intel.com, mripard@kernel.org,
tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
pmladek@suse.com, sergey.senozhatsky@gmail.com,
rostedt@goodmis.org, mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
bsegall@google.com, mgorman@suse.de, songmuchun@bytedance.com,
john.ogness@linutronix.de
Subject: Re: [External] Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule()
Date: Mon, 28 Sep 2020 12:25:59 +0200 [thread overview]
Message-ID: <20200928102559.GF2611@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <688eadd7-4ca3-3e32-3520-25977ff059a6@bytedance.com>
On Mon, Sep 28, 2020 at 06:04:23PM +0800, Chengming Zhou wrote:
> Well, you are lucky. So it's a problem in our printk implementation.
Not lucky; I just kicked it in the groin really hard:
git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git debug/experimental
> The deadlock path is:
>
> printk
> vprintk_emit
> console_unlock
> vt_console_print
> hide_cursor
> bit_cursor
> soft_cursor
> queue_work_on
> __queue_work
> try_to_wake_up
> _raw_spin_lock
> native_queued_spin_lock_slowpath
>
> Looks like it's introduced by this commit:
>
> eaa434defaca1781fb2932c685289b610aeb8b4b
>
> "drm/fb-helper: Add fb_deferred_io support"
Oh gawd, yeah, all the !serial consoles are utter batshit.
Please look at John's last printk rewrite, IIRC it farms all that off to
a kernel thread instead of doing it from the printk() caller's context.
I'm not sure where he hides his latests patches, but I'm sure he'll be
more than happy to tell you.
next prev parent reply other threads:[~2020-09-28 10:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-27 16:11 [PATCH 1/2] printk: Add printk_deferred_{enter, exit} Chengming Zhou
2020-09-27 16:11 ` [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule() Chengming Zhou
2020-09-28 7:32 ` Peter Zijlstra
2020-09-28 7:52 ` Joe Perches
2020-09-28 8:00 ` Peter Zijlstra
2020-09-28 8:06 ` Peter Zijlstra
2020-09-28 8:54 ` [External] " Chengming Zhou
2020-09-28 9:01 ` Peter Zijlstra
2020-09-28 10:04 ` Chengming Zhou
2020-09-28 10:25 ` Peter Zijlstra [this message]
2020-09-28 23:50 ` Sergey Senozhatsky
2020-09-29 14:27 ` Petr Mladek
2020-09-29 15:09 ` Peter Zijlstra
2020-09-30 0:48 ` Sergey Senozhatsky
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