diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2022-10-20 17:51:04 +0200 |
|---|---|---|
| committer | Song Liu <song@kernel.org> | 2022-11-14 09:35:50 -0800 |
| commit | 9487a0f6855c1a28e4e39d41545cd19ed417c015 (patch) | |
| tree | 09b4b8c272be00cdb285275f17b11119bb167643 /drivers/md | |
| parent | 3bd548e5b819b8c0f2c9085de775c5c7bff9052f (diff) | |
| download | linux-9487a0f6855c1a28e4e39d41545cd19ed417c015.tar.bz2 | |
raid5-cache: use try_cmpxchg in r5l_wake_reclaim
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
r5l_wake_reclaim. 86 CMPXCHG instruction returns success in ZF flag, so
this change saves a compare after cmpxchg (and related move instruction in
front of cmpxchg).
Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails. There is no need to re-read the value in the loop.
Note that the value from *ptr should be read using READ_ONCE to prevent
the compiler from merging, refetching or reordering the read.
No functional change intended.
Cc: Song Liu <song@kernel.org>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Song Liu <song@kernel.org>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/raid5-cache.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 832d8566e165..a63023aae21e 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -1565,11 +1565,12 @@ void r5l_wake_reclaim(struct r5l_log *log, sector_t space) if (!log) return; + + target = READ_ONCE(log->reclaim_target); do { - target = log->reclaim_target; if (new < target) return; - } while (cmpxchg(&log->reclaim_target, target, new) != target); + } while (!try_cmpxchg(&log->reclaim_target, &target, new)); md_wakeup_thread(log->reclaim_thread); } |