diff options
| author | linke li | 2024-04-26 18:34:44 +0800 |
|---|---|---|
| committer | Jens Axboe | 2024-04-26 07:40:28 -0600 |
| commit | 6ad0d7e0f4b68f87a98ea2b239123b7d865df86b (patch) | |
| tree | d8ac274dd632519dc9f9694cd631024cfb3eeaa7 /lib | |
| parent | 07d1b99825f40f9c0d93e6b99d79a08d0717bac1 (diff) | |
sbitmap: use READ_ONCE to access map->word
In __sbitmap_queue_get_batch(), map->word is read several times, and
update atomically using atomic_long_try_cmpxchg(). But the first two read
of map->word is not protected.
This patch moves the statement val = READ_ONCE(map->word) forward,
eliminating unprotected accesses to map->word within the function.
It is aimed at reducing the number of benign races reported by KCSAN in
order to focus future debugging effort on harmful races.
Signed-off-by: linke li <lilinke99@qq.com>
Link: https://lore.kernel.org/r/tencent_0B517C25E519D3D002194E8445E86C04AD0A@qq.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/sbitmap.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 92c6b1fd8989..1e453f825c05 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -494,18 +494,18 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags, struct sbitmap_word *map = &sb->map[index]; unsigned long get_mask; unsigned int map_depth = __map_depth(sb, index); + unsigned long val; sbitmap_deferred_clear(map); - if (map->word == (1UL << (map_depth - 1)) - 1) + val = READ_ONCE(map->word); + if (val == (1UL << (map_depth - 1)) - 1) goto next; - nr = find_first_zero_bit(&map->word, map_depth); + nr = find_first_zero_bit(&val, map_depth); if (nr + nr_tags <= map_depth) { atomic_long_t *ptr = (atomic_long_t *) &map->word; - unsigned long val; get_mask = ((1UL << nr_tags) - 1) << nr; - val = READ_ONCE(map->word); while (!atomic_long_try_cmpxchg(ptr, &val, get_mask | val)) ; |