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

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

> 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.

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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