Subject: Re: [PATCH v5 00/45] CPU hotplug: stop_machine()-free CPU hotplug

From: Thomas Gleixner <[email-masked]>
Date: Mon, 18 Feb 2013 11:54:23 +0100 (CET)

On Mon, 18 Feb 2013, Srivatsa S. Bhat wrote:
> Lockup observed while running this patchset, with CPU_IDLE and INTEL_IDLE turned
> on in the .config:
> 
>  smpboot: CPU 1 is now offline
> Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 11
> Pid: 0, comm: swapper/11 Not tainted 3.8.0-rc7+stpmch13-1 #8
> Call Trace:
>  [<ffffffff812aba1e>] do_raw_spin_lock+0x7e/0x150
>  [<ffffffff815a64c1>] _raw_spin_lock_irqsave+0x61/0x70
>  [<ffffffff810c0758>] ? clockevents_notify+0x28/0x150
>  [<ffffffff815a6d37>] ? _raw_spin_unlock_irqrestore+0x77/0x80
>  [<ffffffff810c0758>] clockevents_notify+0x28/0x150
>  [<ffffffff8130459f>] intel_idle+0xaf/0xe0
>  [<ffffffff81472ee0>] ? disable_cpuidle+0x20/0x20
>  [<ffffffff81472ef9>] cpuidle_enter+0x19/0x20
>  [<ffffffff814734c1>] cpuidle_wrap_enter+0x41/0xa0
>  [<ffffffff81473530>] cpuidle_enter_tk+0x10/0x20
>  [<ffffffff81472f17>] cpuidle_enter_state+0x17/0x50
>  [<ffffffff81473899>] cpuidle_idle_call+0xd9/0x290
>  [<ffffffff810203d5>] cpu_idle+0xe5/0x140
>  [<ffffffff8159c603>] start_secondary+0xdd/0xdf

> BUG: spinlock lockup suspected on CPU#2, migration/2/19
>  lock: clockevents_lock+0x0/0x40, .magic: dead4ead, .owner: swapper/8/0, .owner_cpu: 8

Unfortunately there is no back trace for cpu8. That's probably caused
by the watchdog -> panic setting.

So we have no idea why cpu2 and 11 get stuck on the clockevents_lock
and without that information it's impossible to decode.

Thanks,

	tglx