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From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	David Rientjes <rientjes@google.com>,
	David Laight <David.Laight@ACULAB.COM>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Ingo Molnar <mingo@kernel.org>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: __refrigerator() && saved task->state
Date: Wed, 13 Nov 2013 20:11:43 +0100	[thread overview]
Message-ID: <20131113191143.GA24005@redhat.com> (raw)
In-Reply-To: <20131113170724.GA17739@redhat.com>

Sorry for noise, but I am totally confused.

Could you please remind why __refrigerator() saves/restores
task->state?

I can see only one reason: set_freezable() kernel threads which
check kthread_should_stop() and do try_to_freeze() by hand.

But does this save/restore actually help?

For example kauditd_thread() looks obviously racy exactly because
try_to_freeze() can return in TASK_INTERRUPTIBLE state after
wake_up(kauditd_wait) was already called, we can miss an event.

At first glance it would be better to simply kill this logic? If
it was called with ->state != 0, the caller is going to schedule()
and it probably executes the wait_event-like code, in this case
it would me more safe to pretend the task got a spurious wakeup?

(as for kauditd_thread() in particular, it looks wrong in any
 case, even kthread_should_stop() check doesn't look right, it
 needs kthread_freezable_should_stop() afaics).

But I guess I missed something else...

Oleg.


  parent reply	other threads:[~2013-11-13 19:11 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-12 13:53 [PATCH] ipvs: Remove unused variable ret from sync_thread_master() Geert Uytterhoeven
2013-11-12 14:13 ` Peter Zijlstra
2013-11-12 14:21   ` David Laight
2013-11-12 14:31     ` Peter Zijlstra
2013-11-12 14:38       ` David Laight
2013-11-12 16:26       ` Oleg Nesterov
2013-11-12 14:52     ` Peter Zijlstra
2013-11-12 16:21       ` Oleg Nesterov
2013-11-12 16:56         ` oom-kill && frozen() Oleg Nesterov
2013-11-13  3:20           ` Tejun Heo
2013-11-13 17:07             ` Oleg Nesterov
2013-11-13 17:42               ` Peter Zijlstra
2013-11-13 18:15                 ` Oleg Nesterov
2013-11-13 19:11               ` Oleg Nesterov [this message]
2013-11-13 19:14                 ` __refrigerator() && saved task->state Peter Zijlstra
2013-11-13 19:40                   ` Oleg Nesterov
2013-11-12 17:00         ` [PATCH] ipvs: Remove unused variable ret from sync_thread_master() Peter Zijlstra
2013-11-12 18:04           ` Oleg Nesterov

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