From: Jiri Bohac <jbohac@suse.cz>
To: John Stultz <john.stultz@linaro.org>, linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: is printk() safe within a timekeeper_seq write section?
Date: Thu, 6 Mar 2014 18:45:31 +0100 [thread overview]
Message-ID: <20140306174531.GA30634@midget.suse.cz> (raw)
Hi,
I'm looking at the printk call in
__timekeeping_inject_sleeptime(), introduced in cb5de2f8
(time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime)
Is it safe to call printk() while timekeeper_seq is held for
writing?
What about this call chain?
printk
vprintk_emit
console_unlock
up(&console_sem)
__up
wake_up_process
try_to_wake_up
ttwu_do_activate
ttwu_activate
activate_task
enqueue_task
enqueue_task_fair
hrtick_update
hrtick_start_fair
hrtick_start_fair
get_time
ktime_get
--> endless loop on
read_seqcount_retry(&timekeeper_seq, ...)
It looks like an unlikely but possible deadlock.
Or did I overlook something?
Thanks!
--
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, SUSE CZ
next reply other threads:[~2014-03-06 17:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-06 17:45 Jiri Bohac [this message]
2014-03-11 19:29 ` is printk() safe within a timekeeper_seq write section? John Stultz
2014-03-11 21:32 ` Thomas Gleixner
2014-03-11 21:54 ` John Stultz
2014-03-12 6:49 ` Peter Zijlstra
2014-03-12 9:21 ` Jiri Bohac
2014-03-28 0:49 ` John Stultz
2014-03-12 6:46 ` Peter Zijlstra
2014-03-12 14:34 ` Jan Kara
2014-03-12 15:06 ` Peter Zijlstra
2014-03-14 15:13 ` Jan Kara
2014-03-12 13:13 ` Jan Kara
2014-03-12 9:25 ` Peter Zijlstra
2014-03-12 9:18 ` Peter Zijlstra
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