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Re: [Xen-devel] [PATCH] BUG() on soft lockup upon suspend/resume

  • To: Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Mon, 09 Oct 2006 23:22:02 +0100
  • Delivery-date: Mon, 09 Oct 2006 15:33:02 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acbr8VfXllvEHFfkEduJIgANk04WTA==
  • Thread-topic: [Xen-devel] [PATCH] BUG() on soft lockup upon suspend/resume

On 9/10/06 10:22 pm, "Glauber de Oliveira Costa" <gcosta@xxxxxxxxxx> wrote:

> In systems with vcpu > 1, a BUG due to a detected soft lockup seems to be
> triggered after system resume/suspend. This is probably due to the lack of
> seqlocking around the region that does the local time processing.

We do SMP save/restore tests regularly and do not see this issue. It ought
to be avoided by the fact that, when we bring up a CPU, we
touch_softlockup_watchdog() in cpu_bringup(), before enabling interrupts.
For CPU0 on resume, the touch is done in time_resume() in

In general that local accounting work does not need to be done under the
xtime_lock. Native x86 does not take the lock in smp_local_timer_interrupt()
(apic.c) for example.

I think we need to understand the issue you are hitting a bit more before
deciding on the right fix.

 -- Keir

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