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Date: Thu, 14 Jun 2012 17:58:04 +0200
From: Alexander Graf <agraf@suse.de>
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Subject: Re: [Qemu-devel] qemu-system-ppc64 hanging occasionally in disk
	writes
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To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: "<qemu-ppc@nongnu.org>" <qemu-ppc@nongnu.org>, qemu-devel@nongnu.org

[CC'ing qemu-ppc]

On 06/14/2012 05:52 PM, Richard W.M. Jones wrote:
> I found last week that qemu-system-ppc64 (from git) hangs occasionally
> under load, and I have a reproducer for it now.  Unfortunately the
> reproducer really takes a long time to run -- usually I can get a hang
> in under 12 hours.
>
> Here is the reproducer case:
>
>    https://lists.fedoraproject.org/pipermail/ppc/2012-June/001698.html
>
> Notes:
>
> (1) Verified by one other person (other than me).  Happens on both
>      ppc64 and x86-64 host.
>
> (2) Happens with both Fedora guest kernel 3.3.4-5.fc17.ppc64 and kernel
>      3.5.0 that I compiled myself.  The test case above contains 3.3.4-5.
>
> (3) Seems to be a problem in qemu, not the guest.  The reason I think
>      this is because I tried to capture a backtrace of the hang using
>      remote gdb, but gdb just hung when trying to connect to qemu
>      (gdb connects fine before the bug happens).
>
> (4) Judging by guest messages, appears to be happening when writing
>      to the disk.

Can you please try to see if you can repdudice this using vscsi / vio 
instead of virtio? I couldn't quite see why vio would be any more stable 
than virtio though ...

Also, could you please try and see if it works reliably using KVM? Maybe 
we're just encountering some TCG breakage here.


Alex