Re: [Xen-devel] Re: First post-xenbus-change USB patch

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 15 Nov 2005, at 15:37, Ewan Mellor wrote:

> > I did a quick bit of testing and managed to mount the USB key again 
> > etc
> > but had a few problems with module unload and reload.  I think I maybe
> > got hit by the unregister_watch deadlock then
> Yes, we really need to address that one.  The code says
>
>         /* Flush any currently-executing callback, unless we are it. :-) */
>
> (IIRC, that's the deadlock point that Rusty highlighted) but I don't 
> really
> know what this means.  Can you shed some light here on what we ought 
> to be
> doing?
I'd love to see the xenwatch_mutex disappear -- it could well be 
involved in a deadlock situation. It is only used to ensure that an 
unregistered watch is not still executing when 
unregister_xenbus_watch() returns, but that is kind of important if 
e.g., module code is about to get blown away. :-)
I'll have a think about it...

 -- Keir


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