m sends
messages (IN to the host) which are short enough to fit in most
FIFOs.  That means that with some peripheral controller drivers
(evidently not the ones used to verify the notification code!!)
the completion callback can be issued before queue() returns.

The deadlock would come because the completion callback and the
event-issuing code shared a spinlock.  Fix is trivial:  drop
that lock while queueing the message.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Q8S9œ(x