diff options
| author | Keith Busch <kbusch@kernel.org> | 2022-08-25 07:53:12 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-09-01 10:42:41 -0600 |
| commit | 16ede66973c84f890c03584f79158dd5b2d725f5 (patch) | |
| tree | a021cb3e0dbe12dde89734f1c558e29b28758c18 /lib | |
| parent | ddbfc34fcf5d0bc33b006b90c580c56edeb31068 (diff) | |
sbitmap: fix batched wait_cnt accounting
Batched completions can clear multiple bits, but we're only decrementing
the wait_cnt by one each time. This can cause waiters to never be woken,
stalling IO. Use the batched count instead.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215679
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20220825145312.1217900-1-kbusch@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/sbitmap.c | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c index a39b1a877366..2fedf07a9db5 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -599,34 +599,38 @@ static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq) return NULL; } -static bool __sbq_wake_up(struct sbitmap_queue *sbq) +static bool __sbq_wake_up(struct sbitmap_queue *sbq, int nr) { struct sbq_wait_state *ws; - unsigned int wake_batch; - int wait_cnt; + int wake_batch, wait_cnt, cur; ws = sbq_wake_ptr(sbq); - if (!ws) + if (!ws || !nr) return false; - wait_cnt = atomic_dec_return(&ws->wait_cnt); + wake_batch = READ_ONCE(sbq->wake_batch); + cur = atomic_read(&ws->wait_cnt); + do { + if (cur <= 0) + return true; + wait_cnt = cur - nr; + } while (!atomic_try_cmpxchg(&ws->wait_cnt, &cur, wait_cnt)); + /* * For concurrent callers of this, callers should call this function * again to wakeup a new batch on a different 'ws'. */ - if (wait_cnt < 0 || !waitqueue_active(&ws->wait)) + if (!waitqueue_active(&ws->wait)) return true; if (wait_cnt > 0) return false; - wake_batch = READ_ONCE(sbq->wake_batch); - /* * Wake up first in case that concurrent callers decrease wait_cnt * while waitqueue is empty. */ - wake_up_nr(&ws->wait, wake_batch); + wake_up_nr(&ws->wait, max(wake_batch, nr)); /* * Pairs with the memory barrier in sbitmap_queue_resize() to @@ -651,12 +655,11 @@ static bool __sbq_wake_up(struct sbitmap_queue *sbq) return false; } -void sbitmap_queue_wake_up(struct sbitmap_queue *sbq) +void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr) { - while (__sbq_wake_up(sbq)) + while (__sbq_wake_up(sbq, nr)) ; } -EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up); static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag) { @@ -693,7 +696,7 @@ void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset, atomic_long_andnot(mask, (atomic_long_t *) addr); smp_mb__after_atomic(); - sbitmap_queue_wake_up(sbq); + sbitmap_queue_wake_up(sbq, nr_tags); sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(), tags[nr_tags - 1] - offset); } @@ -721,7 +724,7 @@ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, * waiter. See the comment on waitqueue_active(). */ smp_mb__after_atomic(); - sbitmap_queue_wake_up(sbq); + sbitmap_queue_wake_up(sbq, 1); sbitmap_update_cpu_hint(&sbq->sb, cpu, nr); } EXPORT_SYMBOL_GPL(sbitmap_queue_clear); |