Re: [Xen-devel] [PATCH] xen mmu: fix a race window causing leave_mm BUG()

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, May 11, 2011 at 08:34:46PM +0800, Tian, Kevin wrote:
> > From: Ian Campbell [mailto:Ian.Campbell@xxxxxxxxxx]
> > Sent: Wednesday, May 11, 2011 5:44 PM
> > 
> > On Wed, 2011-05-11 at 02:20 +0100, Tian, Kevin wrote:
> > > > From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> > > > Sent: Wednesday, May 11, 2011 4:27 AM
> > > >
> > > > On Fri, Apr 29, 2011 at 12:10:57PM +0800, Tian, Kevin wrote:
> > > > >     xen mmu: fix a race window causing leave_mm BUG()
> > > >
> > > > I've this in mailbox and I am wondering whether this still an issue
> > > > with the
> > > > 2.6.39 type kernels?
> > > > How do you reproduce the failure? When using LVM?
> > >
> > > this issue is reported by Xiaoyun when he did extensive test which
> > > happened occasionally after dozen of hours running. From the
> > > phenomenon and info provided by Xiaoyun, I found this potential race
> > > window and Xiaoyun has verified this patch solving his stability issue.
> > >
> > > the original thread is at:
> > > http://lists.xensource.com/archives/html/xen-devel/2011-04/msg01186.ht
> > > ml
> > >
> > > his kernel is based on 2.6.38, and I checked latest 2.6.39 from your
> > > maintained repo, and same issue still exists.
> > >
> > > btw, I didn't reproduce it myself, and not sure whether Xiaoyun uses
> > > LVM. But I think it has nothing to do with storage type, and a pure mmu
> > design issue.
> > 
> > Is there a specific stack trace (or two) which is associated with this bug? 
> > I'm
> > wondering if http://bugs.debian.org/613073 might be the same thing...
> > 
> 
> If you look into above thread:
> 
> http://lists.xensource.com/archives/html/xen-devel/2011-04/msg00657.html
> 
> [<ffffffff8100e4a4>] drop_other_mm_ref+0x2a/0x53
> 
>  [<ffffffff81087224>] generic_smp_call_function_single_interrupt+0xd8/0xfc
> 
>  [<ffffffff810100e8>] xen_call_function_single_interrupt+0x13/0x28
> 
>  [<ffffffff810a936a>] handle_IRQ_event+0x66/0x120
> 
>  [<ffffffff810aac5b>] handle_percpu_irq+0x41/0x6e
> 
>  [<ffffffff8128c1a8>] __xen_evtchn_do_upcall+0x1ab/0x27d
> 
>  [<ffffffff8128dcf9>] xen_evtchn_do_upcall+0x33/0x46
> 
>  [<ffffffff81013efe>] xen_do_hypervisor_callback+0x1e/0x30

Can you resend the patch to me, based on top of v2.6.39-rc7, with the above
stack dump? And please resend it as an attachment. Your mailer mangles
the patch.

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