diff options
| author | Omar Sandoval <osandov@fb.com> | 2018-02-27 16:56:43 -0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-02-28 12:23:35 -0700 |
| commit | 4ace53f1ed40a5cfee4bdd7614c8a8b2798227ad (patch) | |
| tree | c766967b9ac9c5ae7a04035c0fa182fb27167d33 /lib/sbitmap.c | |
| parent | e9a99a638800af25c7ed006c96fd1dabb99254b7 (diff) | |
sbitmap: use test_and_set_bit_lock()/clear_bit_unlock()
sbitmap_queue_get()/sbitmap_queue_clear() are used for
allocating/freeing a resource, so they should provide acquire/release
barrier semantics, respectively. sbitmap_get() currently contains a full
barrier, which is unnecessary, so use test_and_set_bit_lock() instead of
test_and_set_bit() (these are equivalent on x86_64). sbitmap_clear_bit()
does not imply any barriers, which is incorrect, as accesses of the
resource (e.g., request) could potentially get reordered to after the
clear_bit(). Introduce sbitmap_clear_bit_unlock() and use it for
sbitmap_queue_clear() (this only adds a compiler barrier on x86_64). The
other existing user of sbitmap_clear_bit() (the blk-mq software queue
pending map) is serialized through a spinlock and does not need this.
Reported-by: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'lib/sbitmap.c')
| -rw-r--r-- | lib/sbitmap.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 42b5ca0acf93..e6a9c06ec70c 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -100,7 +100,7 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth, return -1; } - if (!test_and_set_bit(nr, word)) + if (!test_and_set_bit_lock(nr, word)) break; hint = nr + 1; @@ -434,9 +434,9 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) /* * Pairs with the memory barrier in set_current_state() to ensure the * proper ordering of clear_bit()/waitqueue_active() in the waker and - * test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See - * the comment on waitqueue_active(). This is __after_atomic because we - * just did clear_bit() in the caller. + * test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the + * waiter. See the comment on waitqueue_active(). This is __after_atomic + * because we just did clear_bit_unlock() in the caller. */ smp_mb__after_atomic(); @@ -469,7 +469,7 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, unsigned int cpu) { - sbitmap_clear_bit(&sbq->sb, nr); + sbitmap_clear_bit_unlock(&sbq->sb, nr); sbq_wake_up(sbq); if (likely(!sbq->round_robin && nr < sbq->sb.depth)) *per_cpu_ptr(sbq->alloc_hint, cpu) = nr; |