[Xen-devel] Re: [PATCH v4 0/3] Add reference counting to grant notify ioctls

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Oct 27, 2011 at 05:58:46PM -0400, Daniel De Graaf wrote:
> > The current notify ioctls assume that an event channel will not be
> > closed prior to the page being unmapped. If the mappings are associated
> > with an open file descriptor and the application crashes, the
> > notification behavior depends on the close ordering of the file
> > descriptors. To avoid this, event channels now have a reference count
> > that is used by the grant notify ioctls to postpone the close operation
> > until the notification is fired.

OK, it all looks sensible to me. Sticking on my 3.3 queue.
Thx!
> 
> Changes since v3:
>       Avoid race between evtchn_get and evtchn_put
>       (reference count changed to an integer protected by mutex)
> 
> Changes since v2:
>       Avoid possible sleep under spinlock
>       Decrease refcount mismatch errors from BUG to WARN
>       Use reference count to identify userspace-visible event channels
>  
> Changes since v1:
>       Rename evtchn_get/put to match kernel naming conventions
>       Use atomic_t for refcount
> 
> [PATCH 1/3] xen/event: Add reference counting to event channels
> [PATCH 2/3] xen/gntalloc: Change gref_lock to a mutex
> [PATCH 3/3] xen/gnt{dev,alloc}: reserve event channels for notify

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