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| author | Pavel Begunkov <asml.silence@gmail.com> | 2019-05-23 18:39:16 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-07-01 11:57:12 -0600 |
| commit | 417232880c8a646739dbf4666a231505a1917fcb (patch) | |
| tree | db1dc62d7382a6571e0e5ace415281baa1884c43 /lib | |
| parent | 79d08f89bb1b5c2c1ff90d9bb95497ab9e8aa7e0 (diff) | |
| download | linux-417232880c8a646739dbf4666a231505a1917fcb.tar.bz2 | |
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')
| -rw-r--r-- | lib/sbitmap.c | 10 |
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; } |