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

[Jim Fehlig <jfehlig@xxxxxxxx>]

Ian Jackson wrote:
> 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).
>   

And it does.  The event loop lock is released just before invoking the
callback, and re-acquired just after the callback returns.

Jim


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