diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2025-08-14 07:43:26 +0100 |
|---|---|---|
| committer | Tvrtko Ursulin <tursulin@ursulin.net> | 2025-08-15 09:17:11 +0100 |
| commit | 60b006b7cf0dd5e8ee99bd77fb4573e1a3956035 (patch) | |
| tree | 1e889971a940288d69270456d62934cf3eafa705 | |
| parent | 317be9c64215f264740c6dffb0a44216960875b2 (diff) | |
drm/i915/active: Use try_cmpxchg64() in __active_lookup()
Replace this pattern in __active_lookup():
cmpxchg64(*ptr, old, new) == old
... with the simpler and faster:
try_cmpxchg64(*ptr, &old, new)
The x86 CMPXCHG instruction returns success in the ZF flag,
so this change saves a compare after the CMPXCHG.
The patch also improves the explanation of what the code really
does. cmpxchg64() will *succeed* for the winner of the race and
try_cmpxchg64() nicely documents this fact.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20250814064326.95519-1-tvrtko.ursulin@igalia.com
| -rw-r--r-- | drivers/gpu/drm/i915/i915_active.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c index 0dbc4e289300..6b0c1162505a 100644 --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -257,10 +257,9 @@ static struct active_node *__active_lookup(struct i915_active *ref, u64 idx) * claimed the cache and we know that is does not match our * idx. If, and only if, the timeline is currently zero is it * worth competing to claim it atomically for ourselves (for - * only the winner of that race will cmpxchg return the old - * value of 0). + * only the winner of that race will cmpxchg succeed). */ - if (!cached && !cmpxchg64(&it->timeline, 0, idx)) + if (!cached && try_cmpxchg64(&it->timeline, &cached, idx)) return it; } |