sbitmap_deferred_clear() does CAS loop to propagate cleared bits, replace it with equivalent atomic bitwise and. That's slightly faster and makes wait-free instead of lock-free as before.
The atomic can be relaxed (i.e. barrier-less) because following sbitmap_get*() deal with synchronisation, see comments in sbitmap_queue_clear(). It's ok to cast to atomic_long_t, that's what bitops/lock.h does. Signed-off-by: Pavel Begunkov <[email protected]> --- lib/sbitmap.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 4fd877048ba8..c18b518a16ba 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -14,7 +14,7 @@ */ static inline bool sbitmap_deferred_clear(struct sbitmap_word *map) { - unsigned long mask, val; + unsigned long mask; if (!READ_ONCE(map->cleared)) return false; @@ -27,10 +27,8 @@ static inline bool sbitmap_deferred_clear(struct sbitmap_word *map) /* * Now clear the masked bits in our free word */ - do { - val = map->word; - } while (cmpxchg(&map->word, val, val & ~mask) != val); - + atomic_long_andnot(mask, (atomic_long_t *)&map->word); + BUILD_BUG_ON(sizeof(atomic_long_t) != sizeof(map->word)); return true; } -- 2.24.0
