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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Ingo Molnar <mingo@elte.hu>
Subject: Re: [Regression] 2.6.24-git8 (and earlier): Multiple processes stuck in D states after logout from KDE
Date: Thu, 31 Jan 2008 00:42:07 +0100
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Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Steven Rostedt <rostedt@goodmis.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>
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Update.

On Wednesday, 30 of January 2008, Rafael J. Wysocki wrote:
> Hi,
> 
> Recently I've been observing problems with unmounting the /home fs on reboot
> and/or shutdown on two test boxes.
> 
> After some more investigation I've found that this is due to some KDE processes
> stuck in D states after their owner has logged out.
> 
> This happens 100% of the time if there's a suspend/resume cycle before the user
> logs out (ie. the user logs into KDE, works for some time, suspends the box to
> RAM and resmes one or more times and then logs out).  Still, I also observe the
> symptoms on a box that's never suspended.
> 
> I'm not sure how to debug this, so please advise.

After reverting:

commit 37bb6cb4097e29ffee970065b74499cbf10603a3
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: ? Fri Jan 25 21:08:32 2008 +0100

? ? hrtimer: unlock hrtimer_wakeup

I no longer get processes in the D state, but there still is a problem with
artswrapper (this is an openSUSE 10.3 system, x86-64).  Namely,
after a suspend/resume cycle and logging out/logging in the user,
artswrapper gets stuck somewhere, apparently in the running (R) state.
For this reason it blocks any subsequent attempts to suspend.

Here's the relevant trace (from show_state()):

[  522.474919] artswrapper   R  running task        0  4805      1
[  522.474922]  ffff810074cd1f70 0000000000000082 0000000000000296 ffff810074cd1ed8
[  522.474926]  ffffffff80311769 ffff810074cd1f20 ffffffff80701240 ffffffff80701240
[  522.474930]  ffffffff80701240 ffffffff80701240 ffffffff80701240 ffffffff80701240
[  522.474933] Call Trace:
[  522.474940]  [<ffffffff80311769>] ? __up_read+0x8f/0x97
[  522.474963]  [<ffffffff8020c5cf>] retint_careful+0xd/0x21

where, according to gdb,

(gdb) l *__up_read+0x8f
0xffffffff80311769 is in __up_read (/home/rafael/src/linux-2.6/lib/rwsem-spinlock.c:273).
268
269             if (--sem->activity == 0 && !list_empty(&sem->wait_list))
270                     sem = __rwsem_wake_one_writer(sem);
271
272             spin_unlock_irqrestore(&sem->wait_lock, flags);
273     }
274
275     /*
276      * release a write lock on the semaphore
277      */

What gives?

Rafael
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