diff options
| author | Omar Sandoval <osandov@fb.com> | 2018-02-27 16:56:43 -0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-02-28 12:23:35 -0700 |
| commit | 4ace53f1ed40a5cfee4bdd7614c8a8b2798227ad (patch) | |
| tree | c766967b9ac9c5ae7a04035c0fa182fb27167d33 /include | |
| parent | e9a99a638800af25c7ed006c96fd1dabb99254b7 (diff) | |
sbitmap: use test_and_set_bit_lock()/clear_bit_unlock()
sbitmap_queue_get()/sbitmap_queue_clear() are used for
allocating/freeing a resource, so they should provide acquire/release
barrier semantics, respectively. sbitmap_get() currently contains a full
barrier, which is unnecessary, so use test_and_set_bit_lock() instead of
test_and_set_bit() (these are equivalent on x86_64). sbitmap_clear_bit()
does not imply any barriers, which is incorrect, as accesses of the
resource (e.g., request) could potentially get reordered to after the
clear_bit(). Introduce sbitmap_clear_bit_unlock() and use it for
sbitmap_queue_clear() (this only adds a compiler barrier on x86_64). The
other existing user of sbitmap_clear_bit() (the blk-mq software queue
pending map) is serialized through a spinlock and does not need this.
Reported-by: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/sbitmap.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 0dcc60e820de..841585f6e5f2 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -171,6 +171,8 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth); * starting from the last allocated bit. This is less efficient * than the default behavior (false). * + * This operation provides acquire barrier semantics if it succeeds. + * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin); @@ -300,6 +302,12 @@ static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr) clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); } +static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb, + unsigned int bitnr) +{ + clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); +} + static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) { return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); |