From 8537b12034cf1fd3fab3da2c859d71f76846fae9 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Tue, 17 Jun 2014 22:12:35 -0700 Subject: [PATCH] blk-mq: bitmap tag: fix races on shared ::wake_index fields Fix racy updates of shared blk_mq_bitmap_tags::wake_index and blk_mq_hw_ctx::wake_index fields. Cc: Ming Lei Signed-off-by: Alexander Gordeev Signed-off-by: Jens Axboe --- block/blk-mq-tag.c | 32 +++++++++++++++++++++----------- block/blk-mq-tag.h | 2 +- include/linux/blk-mq.h | 2 +- 3 files changed, 23 insertions(+), 13 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 1aab39f71d95..6deb13055490 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -43,9 +43,16 @@ bool blk_mq_has_free_tags(struct blk_mq_tags *tags) return bt_has_free_tags(&tags->bitmap_tags); } -static inline void bt_index_inc(unsigned int *index) +static inline int bt_index_inc(int index) { - *index = (*index + 1) & (BT_WAIT_QUEUES - 1); + return (index + 1) & (BT_WAIT_QUEUES - 1); +} + +static inline void bt_index_atomic_inc(atomic_t *index) +{ + int old = atomic_read(index); + int new = bt_index_inc(old); + atomic_cmpxchg(index, old, new); } /* @@ -69,14 +76,14 @@ static void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags) int i, wake_index; bt = &tags->bitmap_tags; - wake_index = bt->wake_index; + wake_index = atomic_read(&bt->wake_index); for (i = 0; i < BT_WAIT_QUEUES; i++) { struct bt_wait_state *bs = &bt->bs[wake_index]; if (waitqueue_active(&bs->wait)) wake_up(&bs->wait); - bt_index_inc(&wake_index); + wake_index = bt_index_inc(wake_index); } } @@ -212,12 +219,14 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx) { struct bt_wait_state *bs; + int wait_index; if (!hctx) return &bt->bs[0]; - bs = &bt->bs[hctx->wait_index]; - bt_index_inc(&hctx->wait_index); + wait_index = atomic_read(&hctx->wait_index); + bs = &bt->bs[wait_index]; + bt_index_atomic_inc(&hctx->wait_index); return bs; } @@ -313,18 +322,19 @@ static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt) { int i, wake_index; - wake_index = bt->wake_index; + wake_index = atomic_read(&bt->wake_index); for (i = 0; i < BT_WAIT_QUEUES; i++) { struct bt_wait_state *bs = &bt->bs[wake_index]; if (waitqueue_active(&bs->wait)) { - if (wake_index != bt->wake_index) - bt->wake_index = wake_index; + int o = atomic_read(&bt->wake_index); + if (wake_index != o) + atomic_cmpxchg(&bt->wake_index, o, wake_index); return bs; } - bt_index_inc(&wake_index); + wake_index = bt_index_inc(wake_index); } return NULL; @@ -344,7 +354,7 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag) bs = bt_wake_ptr(bt); if (bs && atomic_dec_and_test(&bs->wait_cnt)) { atomic_set(&bs->wait_cnt, bt->wake_cnt); - bt_index_inc(&bt->wake_index); + bt_index_atomic_inc(&bt->wake_index); wake_up(&bs->wait); } } diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 98696a65d4d4..6206ed17ef76 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -24,7 +24,7 @@ struct blk_mq_bitmap_tags { unsigned int map_nr; struct blk_align_bitmap *map; - unsigned int wake_index; + atomic_t wake_index; struct bt_wait_state *bs; }; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index a002cf191427..eb726b9c5762 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -42,7 +42,7 @@ struct blk_mq_hw_ctx { unsigned int nr_ctx; struct blk_mq_ctx **ctxs; - unsigned int wait_index; + atomic_t wait_index; struct blk_mq_tags *tags; -- 2.20.1