From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: ksummit-discuss@lists.linuxfoundation.org
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Viresh Kumar <viresh.kumar@linaro.org>, Tejun Heo <tj@kernel.org>,
Jiri Kosina <jkosina@suse.com>
Subject: Re: [Ksummit-discuss] [TECH TOPIC] asynchronous printk
Date: Wed, 21 Sep 2016 13:41:56 +0900 [thread overview]
Message-ID: <20160921044156.GA486@swordfish> (raw)
In-Reply-To: <20160719034717.GA24189@swordfish>
Hello,
a small addition to [1]
On (07/19/16 12:47), Sergey Senozhatsky wrote:
> What I have on my list is:
> - synchronous printk()
> - synchronous console_unlock()
> - console semaphore
Petr Mladek came up with a nice summary [2] of the problems that we
discussed (with a small update from my side [3]). So I would like to
add one more issue to the list, that is, however, not related to async
printk: recursive printk calls. There is a tiny set of cases when
printk can correctly handle recursive printk calls, the rest lead to
deadlock. Those problems, may be, not commonly seen, we had two or three
reports via the public mailing list in the past year; and I've seen 4-5
reports in internal bug tracker (not all of those errors were due to
incorrect printk usage. An unfortunate ARM imprecise abort [4] delivered
while the CPU is in printk->console_unlock->try_to_wake_up under the p->pi_lock
is enough to deadlock the system).
There a several ideas how to try to address those issues that I'm aware
of [5],[6],[7] and, I'm quite sure, even more ideas that I'm not aware of.
Would be interesting to discuss it.
[1] https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2016-July/002740.html
[2] https://marc.info/?l=linux-kernel&m=147263639304079
[3] https://marc.info/?l=linux-kernel&m=147264799407718&w=2
[4] http://infocenter.arm.com/help/topic/com.arm.doc.faqs/14809.html
[5] https://marc.info/?l=linux-kernel&m=147158843319944
[6] https://marc.info/?l=linux-kernel&m=147183933104154
[7] https://marc.info/?l=linux-kernel&m=145440084915204
> The list of potential attendees
> (not in any particular order, most likely incomplete)
>
> Jan Kara
> Petr Mladek
> Andrew Morton
> Jiri Kosina
> Tejun Heo
> Hannes Reinecke
> Viresh Kumar
> Steven Rostedt
> Sergey Senozhatsky
-ss
next prev parent reply other threads:[~2016-09-21 4:42 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-19 3:47 [Ksummit-discuss] [TECH TOPIC] asynchronous printk Sergey Senozhatsky
2016-07-19 3:56 ` Viresh Kumar
2016-07-19 6:17 ` Hannes Reinecke
2016-07-19 6:49 ` Josh Triplett
2016-07-19 7:02 ` Hannes Reinecke
2016-07-19 7:11 ` Geert Uytterhoeven
2016-07-20 6:02 ` Jan Kara
2016-07-20 22:54 ` Josh Triplett
2016-07-21 0:46 ` Sergey Senozhatsky
2016-07-21 1:12 ` Josh Triplett
2016-07-19 7:33 ` Sergey Senozhatsky
2016-07-19 7:38 ` Hannes Reinecke
2016-07-19 7:46 ` Sergey Senozhatsky
2016-07-19 8:02 ` Hannes Reinecke
2016-07-19 8:23 ` Sergey Senozhatsky
2016-07-21 10:36 ` David Woodhouse
2016-07-21 12:31 ` Jan Kara
2016-07-28 2:55 ` Steven Rostedt
2016-07-20 6:09 ` Jan Kara
2016-07-19 7:46 ` Christian Borntraeger
2016-07-19 7:53 ` Christian Borntraeger
2016-07-19 13:55 ` Jan Kara
2016-07-28 2:59 ` Steven Rostedt
2016-07-28 4:12 ` Sergey Senozhatsky
2016-07-28 13:02 ` Steven Rostedt
2016-07-20 3:35 ` Wangnan (F)
2016-07-21 1:16 ` Andy Lutomirski
2016-07-21 1:52 ` Wangnan (F)
2016-07-21 5:59 ` Hannes Reinecke
2016-07-21 10:31 ` David Woodhouse
2016-07-21 11:19 ` Josh Triplett
2016-07-21 11:59 ` David Woodhouse
2016-07-21 14:21 ` Josh Triplett
2016-07-21 14:40 ` David Woodhouse
2016-07-28 3:05 ` Steven Rostedt
2016-08-02 11:59 ` Petr Mladek
2016-07-21 15:05 ` Andy Lutomirski
2016-07-26 14:40 ` David Woodhouse
2016-07-26 15:44 ` Benjamin Herrenschmidt
2016-07-26 21:00 ` Andy Lutomirski
2016-07-27 0:03 ` David Woodhouse
2016-07-27 1:16 ` Sergey Senozhatsky
2016-07-21 10:28 ` David Woodhouse
2016-07-19 14:45 ` James Bottomley
2016-07-19 14:55 ` Sergey Senozhatsky
2016-07-19 17:58 ` James Bottomley
2016-07-19 18:24 ` Viresh Kumar
2016-07-20 2:08 ` Sergey Senozhatsky
2016-07-20 6:14 ` Jan Kara
2016-09-21 4:41 ` Sergey Senozhatsky [this message]
2016-10-31 6:54 ` Sergey Senozhatsky
2016-10-31 13:56 ` Theodore Ts'o
2016-10-31 13:59 ` Jiri Kosina
2016-10-31 14:56 ` [Ksummit-discuss] [TECH TOPIC] printk considered harmful (was: [TECH TOPIC] asynchronous printk) Sergey Senozhatsky
2016-10-31 16:18 ` Theodore Ts'o
2016-10-31 18:21 ` Sergey Senozhatsky
2016-10-31 18:26 ` [Ksummit-discuss] [TECH TOPIC] printk considered harmful Hannes Reinecke
2016-10-31 20:28 ` [Ksummit-discuss] [TECH TOPIC] printk considered harmful (was: [TECH TOPIC] asynchronous printk) Jan Kara
2016-11-01 12:27 ` [Ksummit-discuss] [TECH TOPIC] printk considered harmful Hannes Reinecke
2016-11-01 17:50 ` [Ksummit-discuss] [TECH TOPIC] printk considered harmful (was: [TECH TOPIC] asynchronous printk) Sergey Senozhatsky
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