K 10
svn:author
V 7
delphij
K 8
svn:date
V 27
2015-04-19T23:31:00.389787Z
K 7
svn:log
V 756
In r256613, taskqueue_enqueue_locked() have been modified to release the
task queue lock before returning.  In r276665, taskqueue_drain_all() will
call taskqueue_enqueue_locked() to insert the barrier task into the queue,
but did not reacquire the lock after it but later code expects the lock
still being held (e.g. TQ_SLEEP()).

The barrier task is special and if we release then reacquire the lock,
there would be a small race window where a high priority task could sneak
into the queue.  Looking more closely, the race seems to be tolerable but
is undesirable from semantics standpoint.

To solve this, in taskqueue_drain_tq_queue(), instead of directly calling
taskqueue_enqueue_locked(), insert the barrier task directly without
releasing the lock.

END