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Re: [libvirt] [PATCH 3/4] use monitor fd for domain shutdown



On Tue, Jan 20, 2009 at 08:17:07AM +0100, Guido G?nther wrote:
> Hi,
> On Mon, Jan 19, 2009 at 01:38:22PM +0000, Daniel P. Berrange wrote:
> > >      /* Got them all, so now open the monitor console */
> > > -    ret = qemudOpenMonitor(conn, vm, monitor);
> > > +    qemuDriverLock(driver);
> > > +    ret = qemudOpenMonitor(conn, driver, vm, monitor, 0);
> > > +    qemuDriverUnlock(driver);
> > 
> > What are the lock/unlock calls here for ? They will cause the whole
> > driver to deadlock, because they're violating the rule that a domain
> > lock must not be held while acquiring the driver lock. AFAICT in the
> > qemudOpenMonitor() method you are just passing the 'driver' object
> > straight through to the 'virEventAddHandle' method - since you are
> > not using any data fields in it, locking is not required.
> I looked at HACKING and couldn't find any explanation of the locking
> rules so I added those. They're bogus. Dropped in the new attached
> version.

Yes, I need to write a doc about threading - its too long to put into
the HACKING file directly.


ACK, this looks good now.

Daniel
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