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Date: Fri, 31 Aug 2012 20:02:57 -0300
From: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: rcu_bh stalls on 3.2.28
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Just got one of these:

kernel: INFO: rcu_bh detected stall on CPU 2 (t=0 jiffies)
kernel: Pid: 0, comm: swapper/2 Not tainted 3.2.28+ #2
kernel: Call Trace:
kernel: <IRQ>  [<ffffffff810d1609>] __rcu_pending+0x159/0x400
kernel: [<ffffffff810d20bb>] rcu_check_callbacks+0x9b/0x120
kernel: [<ffffffff81089673>] update_process_times+0x43/0x80
kernel: [<ffffffff810a836f>] tick_sched_timer+0x5f/0xb0
kernel: [<ffffffff8109c097>] __run_hrtimer.isra.30+0x57/0x100
kernel: [<ffffffff8109c8f5>] hrtimer_interrupt+0xe5/0x220
kernel: [<ffffffff8104ce14>] smp_apic_timer_interrupt+0x64/0xa0
kernel: [<ffffffff8159b5cb>] apic_timer_interrupt+0x6b/0x70
kernel: <EOI>  [<ffffffff81315645>] ? intel_idle+0xe5/0x140
kernel: [<ffffffff81315623>] ? intel_idle+0xc3/0x140
kernel: [<ffffffff814420ee>] cpuidle_idle_call+0x8e/0xf0
kernel: [<ffffffff81032425>] cpu_idle+0xa5/0x110
kernel: [<ffffffff8158a9ac>] start_secondary+0x1e5/0x1ec

There are previous reports of these weird rcu_bh stalls with t=0 in the 3.2
and 3.3 branches as well:

https://lkml.org/lkml/2012/2/18/34
http://lkml.org/lkml/2012/3/28/175

another data point:
https://bugzilla.redhat.com/show_bug.cgi?id=806610

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh