From: Joe Perches <joe@perches.com>
To: Peter Zijlstra <peterz@infradead.org>,
Chengming Zhou <zhouchengming@bytedance.com>
Cc: 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
Subject: Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule()
Date: Mon, 28 Sep 2020 00:52:44 -0700 [thread overview]
Message-ID: <0e8e87e25c90339fe790252626855cbb47bc2c08.camel@perches.com> (raw)
In-Reply-To: <20200928073202.GA2611@hirez.programming.kicks-ass.net>
On Mon, 2020-09-28 at 09:32 +0200, Peter Zijlstra wrote:
> On Mon, Sep 28, 2020 at 12:11:30AM +0800, Chengming Zhou wrote:
> > The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be
> > deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause
> > deadlock on rq lock in the printk path.
[]
> NAK printk_deferred is an abomination, kill that.
Didn't you introduce it?
Should you be complaining to yourself?
---
commit 3ccf3e8306156a28213adc720aba807e9a901ad5
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Feb 27 10:47:00 2012 +0100
printk/sched: Introduce special printk_sched() for those awkward moments
There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.
This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
commit aac74dc495456412c4130a1167ce4beb6c1f0b38
Author: John Stultz <john.stultz@linaro.org>
Date: Wed Jun 4 16:11:40 2014 -0700
printk: rename printk_sched to printk_deferred
After learning we'll need some sort of deferred printk functionality in
the timekeeping core, Peter suggested we rename the printk_sched function
so it can be reused by needed subsystems.
This only changes the function name. No logic changes.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
next prev parent reply other threads:[~2020-09-28 7:52 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 [this message]
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
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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