linux-kernel - INFO: task rcu_kthread:6 blocked for more than 120 seconds.

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Message-ID: <20110112174300.GA6504@flint.arm.linux.org.uk>
Date:	Wed, 12 Jan 2011 17:43:00 +0000
From:	Russell King <rmk@....linux.org.uk>
To:	Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: INFO: task rcu_kthread:6 blocked for more than 120 seconds.

I'm seeing rcu_kthread get stuck from time to time on ARM Versatile PB
(ARM926).  Kernel is based upon commit 9e9bc973 (immediately prior to
the merge of the OMAP tree.)

~ # ps aux|grep rcu
root         6  0.0  0.0      0     0 ?        S    02:31   0:01 [rcu_kthread]
root       502  9.0  0.3   3740   472 ttyAMA0  S+   02:59   0:00 grep rcu
~ # ps aux|grep rcu
root         6  0.0  0.0      0     0 ?        D    02:31   0:01 [rcu_kthread]
root       504  0.0  0.3   3740   472 ttyAMA0  S+   03:00   0:00 grep rcu
~ # ps aux|grep rcu
root         6  0.0  0.0      0     0 ?        D    02:31   0:01 [rcu_kthread]
root       506  0.0  0.3   3740   472 ttyAMA0  S+   03:00   0:00 grep rcu
~ # ps aux|grep rcu
root         6  0.0  0.0      0     0 ?        D    02:31   0:01 [rcu_kthread]
root       508  0.0  0.3   3740   472 ttyAMA0  S+   03:00   0:00 grep rcu
~ # cat /proc/6/wchan
rcu_kthread
~ # INFO: task rcu_kthread:6 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
rcu_kthread     D c02c6684     0     6      2 0x00000000
Backtrace:
[<c02c6388>] (schedule+0x0/0x354) from [<c00836a0>] (rcu_kthread+0x78/0xf4)
[<c0083628>] (rcu_kthread+0x0/0xf4) from [<c00633ac>] (kthread+0x88/0x90)
[<c0063324>] (kthread+0x0/0x90) from [<c004d12c>] (do_exit+0x0/0x5f8)
 r7:00000013 r6:c004d12c r5:c0063324 r4:c181df28
no locks held by rcu_kthread/6.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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