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

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [PATCH] fix race condition between libvirtd event 
handling and libxl fd deregister"):
> 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?

Yes, I think that's what Bamvor meant but I don't think it's correct
that such a lock eliminates the race.  libvirt has to release that
lock before making the callback (to follow the libxl locking rules
which are necessary to avoid deadlock).

I'm not surprised that the original patch makes Bamvor's symptoms go
away.  Bamvor had one of the possible races (the fd-related one) but
not the other.

Ian.

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