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authorPavel Begunkov <asml.silence@gmail.com>2019-05-23 18:39:16 +0300
committerJens Axboe <axboe@kernel.dk>2019-07-01 11:57:12 -0600
commit417232880c8a646739dbf4666a231505a1917fcb (patch)
treedb1dc62d7382a6571e0e5ace415281baa1884c43 /lib/sbitmap.c
parent79d08f89bb1b5c2c1ff90d9bb95497ab9e8aa7e0 (diff)
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sbitmap: Replace cmpxchg with xchg
cmpxchg() with an immediate value could be replaced with less expensive xchg(). The same true if new value don't _depend_ on the old one. In the second block, atomic_cmpxchg() return value isn't checked, so after atomic_cmpxchg() -> atomic_xchg() conversion it could be replaced with atomic_set(). Comparison with atomic_read() in the second chunk was left as an optimisation (if that was the initial intention). Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'lib/sbitmap.c')
-rw-r--r--lib/sbitmap.c10
1 files changed, 3 insertions, 7 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 54f57cd117c6..969e5400a615 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -26,9 +26,7 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
/*
* First get a stable cleared mask, setting the old mask to 0.
*/
- do {
- mask = sb->map[index].cleared;
- } while (cmpxchg(&sb->map[index].cleared, mask, 0) != mask);
+ mask = xchg(&sb->map[index].cleared, 0);
/*
* Now clear the masked bits in our free word
@@ -516,10 +514,8 @@ static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
struct sbq_wait_state *ws = &sbq->ws[wake_index];
if (waitqueue_active(&ws->wait)) {
- int o = atomic_read(&sbq->wake_index);
-
- if (wake_index != o)
- atomic_cmpxchg(&sbq->wake_index, o, wake_index);
+ if (wake_index != atomic_read(&sbq->wake_index))
+ atomic_set(&sbq->wake_index, wake_index);
return ws;
}