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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-10-19 16:08:50 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-10-27 10:35:41 +0200 |
| commit | d0c006402e7941558e5283ae434e2847c7999378 (patch) | |
| tree | b55cbec0a50b075fd546c6713d83d65f8b67d290 /kernel/jump_label.c | |
| parent | 247f34f7b80357943234f93f247a1ae6b6c3a740 (diff) | |
| download | linux-d0c006402e7941558e5283ae434e2847c7999378.tar.gz linux-d0c006402e7941558e5283ae434e2847c7999378.tar.bz2 linux-d0c006402e7941558e5283ae434e2847c7999378.zip | |
jump_label: Use atomic_try_cmpxchg() in static_key_slow_inc_cpuslocked()
Use atomic_try_cmpxchg() instead of atomic_cmpxchg (*ptr, old, new) ==
old in static_key_slow_inc_cpuslocked(). 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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221019140850.3395-1-ubizjak@gmail.com
Diffstat (limited to 'kernel/jump_label.c')
| -rw-r--r-- | kernel/jump_label.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c index 714ac4c3b556..4d6c6f5f60db 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -115,8 +115,6 @@ EXPORT_SYMBOL_GPL(static_key_count); void static_key_slow_inc_cpuslocked(struct static_key *key) { - int v, v1; - STATIC_KEY_CHECK_USE(key); lockdep_assert_cpus_held(); @@ -132,11 +130,9 @@ void static_key_slow_inc_cpuslocked(struct static_key *key) * so it counts as "enabled" in jump_label_update(). Note that * atomic_inc_unless_negative() checks >= 0, so roll our own. */ - for (v = atomic_read(&key->enabled); v > 0; v = v1) { - v1 = atomic_cmpxchg(&key->enabled, v, v + 1); - if (likely(v1 == v)) + for (int v = atomic_read(&key->enabled); v > 0; ) + if (likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1))) return; - } jump_label_lock(); if (atomic_read(&key->enabled) == 0) { |