If two events occur back-to-back (e.g., client-reregister and LID
change), both may pass the spinlock-protected code above before the
scheduled work updates the port->sm_ah handle. Then if the scheduled
work ends up running twice, the second operation will then find a
non-NULL port->sm_ah, and will simply overwrite it in update_sm_ah --
resulting in an AH leak.
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il> Signed-off-by: Roland Dreier <rolandd@cisco.com>