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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-07-12 17:05:47 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-07-12 22:38:52 +0200 |
| commit | f4b1e27db49c8b985b116aa99481b4c6a4342ed4 (patch) | |
| tree | 00b3861f47de1e179c300fc038c78fc1a3854a5f /block/blk-rq-qos.c | |
| parent | blk-mq: don't create hctx debugfs dir until q->debugfs_dir is created (diff) | |
| download | linux-f4b1e27db49c8b985b116aa99481b4c6a4342ed4.tar.xz linux-f4b1e27db49c8b985b116aa99481b4c6a4342ed4.zip | |
block/rq_qos: Use atomic_try_cmpxchg in atomic_inc_below
Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old in
atomic_inc_below. x86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move instruction
in front of cmpxchg).
Also, atomic_try_cmpxchg implicitly assigns old *ptr value to "old" when
cmpxchg fails, enabling further code simplifications.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20220712150547.5786-1-ubizjak@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-rq-qos.c')
| -rw-r--r-- | block/blk-rq-qos.c | 10 |
1 files changed, 2 insertions, 8 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index d3a75693adbf..88f0fe7dcf54 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -10,16 +10,10 @@ static bool atomic_inc_below(atomic_t *v, unsigned int below) { unsigned int cur = atomic_read(v); - for (;;) { - unsigned int old; - + do { if (cur >= below) return false; - old = atomic_cmpxchg(v, cur, cur + 1); - if (old == cur) - break; - cur = old; - } + } while (!atomic_try_cmpxchg(v, &cur, cur + 1)); return true; } |