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To:Serge Hallyn From:Daniel Veillard Subject:Re: [libvirt] [PATCH] fix deadlock when qemu cannot start Date:Fri, 30 Mar 2012 23:45:38 +0800
 

On Fri, Mar 30, 2012 at 08:45:35AM -0500, Serge Hallyn wrote:
> Quoting Daniel Veillard (veillard@redhat.com):
> > On Fri, Mar 16, 2012 at 02:37:42PM +0800, Wen Congyang wrote:
> > > When qemu cannot start, we may call qemuProcessStop() twice.
> > > We have check whether the vm is running at the beginning of
> > > qemuProcessStop() to avoid libvirt deadlock. We call
> > > qemuProcessStop() with driver and vm locked. It seems that
> > > we can avoid libvirt deadlock. But unfortunately we may
> > > unlock driver and vm in the function qemuProcessKill() while
> > > vm->def->id is not -1. So qemuProcessStop() will be run twice,
> > > and monitor will be freed unexpectedly. So we should set
> > > vm->def->id to -1 at the beginning of qemuProcessStop().
>
> Oh, uh, Huh. This seems like it could be responsible for what I was
> reporting a few days ago (*1). I spent most of yesterday trying to
> track it down, only to finally realize that the QemuProcessStart would
> silently die at various places. So i was getting ready to send an email
> postulating that what's happening is that a virsh list starts, then
> a virsh start starts, and when the virsh list ends it somehow causes
> the virsh start to be killed.
>
> I'll test and see if this patch fixes it.

I guess I need to resurect my patch checker, tune it and
make it send warning on patches not ACK'ed or reviewed automatically,
or even better make it a web page to avoid boring people.
http://libvirt.org/git/?p=patchchecker.git;a=summary

I had that patch on my radar and though I took an awful long time
to review it it's there.

BTW I'm late for rc2, I will make it tomorrow I guess, sorry about
it this is due to events out of my control :-\

Daniel

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Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
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http://veillard.com/ | virtualization library http://libvirt.org/

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