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block: Add a comment above queue_lockdep_assert_held()

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Add a comment above the queue_lockdep_assert_held() macro that
explains the purpose of the q->queue_lock test.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2017-06-20 11:15:44 -07:00 committed by Jens Axboe
parent c3a148d20a
commit 9e0c829906
1 changed files with 7 additions and 0 deletions
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7
include/linux/blkdev.h
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@ -635,6 +635,13 @@ struct request_queue {
(1 << QUEUE_FLAG_SAME_COMP) | \
(1 << QUEUE_FLAG_POLL))
/*
* @q->queue_lock is set while a queue is being initialized. Since we know
* that no other threads access the queue object before @q->queue_lock has
* been set, it is safe to manipulate queue flags without holding the
* queue_lock if @q->queue_lock == NULL. See also blk_alloc_queue_node() and
* blk_init_allocated_queue().
*/
static inline void queue_lockdep_assert_held(struct request_queue *q)
{
if (q->queue_lock)