Re: [Xen-devel] [PATCH] fix race condition between libvirtd event handling and libxl fd deregister

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-12-07 at 19:11 +0000, Ian Jackson wrote:
> Ian Campbell writes ("Re: [PATCH] fix race condition between libvirtd event 
> handling and libxl fd deregister"):
> > Can we provide, or (more likely) require the application to provide, a
> > lock (perhaps per-event or, again more likely, per-event-loop) which
> > must be held while processing callbacks and also while events are being
> > registered/unregistered with the application's event handling subsystem?
> > With such a lock in place the application would be able to guarantee
> > that having returned from the deregister hook any further events would
> > be seen as spurious events by its own event processing loop.
> 
> I think this might be difficult to get right without deadlocks.

I took Bamvor's most recent response to mean that a per-event lock was
already in place in libvirt and inferred that this was the reason why
the originally proposed one line fix worked for them. Perhaps I
misunderstood?

Ian.


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