diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2024-05-23 11:19:26 +0200 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2024-07-14 19:00:12 -0400 |
| commit | 68573b936d3fceda9cd5cce3a577e035d19ad426 (patch) | |
| tree | 872f291bf9b8d6f439c9d0a5bd372d42557e8e6b /fs/bcachefs/btree_cache.c | |
| parent | e76a2b65b0565f55ea668ec46d54f6a00b8ea9fc (diff) | |
bcachefs: Use try_cmpxchg() family of functions instead of cmpxchg()
Use try_cmpxchg() family of functions instead of
cmpxchg (*ptr, old, new) == old. 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, try_cmpxchg() implicitly assigns old *ptr value to "old" when
cmpxchg fails. There is no need to re-read the value in the loop.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs/bcachefs/btree_cache.c')
| -rw-r--r-- | fs/bcachefs/btree_cache.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c index 4f5e411771ba..6a9b248217a0 100644 --- a/fs/bcachefs/btree_cache.c +++ b/fs/bcachefs/btree_cache.c @@ -602,8 +602,8 @@ int bch2_btree_cache_cannibalize_lock(struct btree_trans *trans, struct closure struct btree_cache *bc = &c->btree_cache; struct task_struct *old; - old = cmpxchg(&bc->alloc_lock, NULL, current); - if (old == NULL || old == current) + old = NULL; + if (try_cmpxchg(&bc->alloc_lock, &old, current) || old == current) goto success; if (!cl) { @@ -614,8 +614,8 @@ int bch2_btree_cache_cannibalize_lock(struct btree_trans *trans, struct closure closure_wait(&bc->alloc_wait, cl); /* Try again, after adding ourselves to waitlist */ - old = cmpxchg(&bc->alloc_lock, NULL, current); - if (old == NULL || old == current) { + old = NULL; + if (try_cmpxchg(&bc->alloc_lock, &old, current) || old == current) { /* We raced */ closure_wake_up(&bc->alloc_wait); goto success; |