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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-07-12 17:44:55 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-07-12 23:46:03 +0200 |
| commit | 96388f57d2aad9836b2c589181fa1dbaba4066b4 (patch) | |
| tree | 8d55b77e103b15559c7b64e034ca5ea0df21ea0e /block/blk-cgroup.c | |
| parent | blk-iolatency: Use atomic{,64}_try_cmpxchg (diff) | |
| download | linux-96388f57d2aad9836b2c589181fa1dbaba4066b4.tar.xz linux-96388f57d2aad9836b2c589181fa1dbaba4066b4.zip | |
blk-cgroup: Use atomic{,64}_try_cmpxchg
Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old
in blkcg_unuse_delay, blkcg_set_delay and blkcg_clear_delay and
atomic64_try_cmpxchg in blkcg_scale_delay. 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/20220712154455.66868-1-ubizjak@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 27a2d0ca0c70..869af9d72bcf 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1700,7 +1700,7 @@ static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now) * everybody is happy with their IO latencies. */ if (time_before64(old + NSEC_PER_SEC, now) && - atomic64_cmpxchg(&blkg->delay_start, old, now) == old) { + atomic64_try_cmpxchg(&blkg->delay_start, &old, now)) { u64 cur = atomic64_read(&blkg->delay_nsec); u64 sub = min_t(u64, blkg->last_delay, now - old); int cur_use = atomic_read(&blkg->use_delay); |