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Date: Thu, 9 Oct 2008 09:24:51 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andi Kleen <andi@firstfloor.org>
cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, mingo@elte.hu,
       linux-kernel@vger.kernel.org, rjw@sisk.pl, dipankar@in.ibm.com
Subject: Re: RCU hang on cpu re-hotplug with 2.6.27rc8
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On Thu, 9 Oct 2008, Andi Kleen wrote:
> It actually does. The stall detector makes the online echo return after three seconds,
> although it's not 100% clear to me why.
> 
> here's the backtrace
> 
> RCU detected CPU 14 stall (t=4295149800/5928 jiffies)
> Pid: 0, comm: swapper Not tainted 2.6.27-rc9 #5
> 
> Call Trace:
>  <IRQ>  [<ffffffff8025d188>] __rcu_pending+0x6e/0x1d9
>  [<ffffffff8025d329>] rcu_pending+0x36/0x6e
>  [<ffffffff8023b480>] update_process_times+0x37/0x5b
>  [<ffffffff8024be72>] tick_periodic+0x68/0x74
>  [<ffffffff8024be9f>] tick_handle_periodic+0x21/0x66
>  [<ffffffff8021bcd2>] smp_apic_timer_interrupt+0x8a/0xa8
>  [<ffffffff8020bfe6>] apic_timer_interrupt+0x66/0x70
>  <EOI>  [<ffffffff803adb39>] ? acpi_safe_halt+0x2b/0x3e
>  [<ffffffff803adbfa>] ? acpi_idle_enter_c1+0xae/0x102
>  [<ffffffff804ffdd6>] ? cpuidle_idle_call+0x70/0xa2
>  [<ffffffff8020a097>] ? cpu_idle+0x7e/0x9c
>  [<ffffffff805bef4a>] ? start_secondary+0x157/0x15c
> 
> Timer issue?

Hmm, this is periodic mode so rather unlikely, but who knows. Does
this happen with nohz and/or highres as well ?

Thanks,

	tglx