diff options
Diffstat (limited to 'block/ll_rw_blk.c')
| -rw-r--r-- | block/ll_rw_blk.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index a15845c164f..ed39313c408 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -1075,12 +1075,6 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq) */ return; - if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) { - printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", - __FUNCTION__, tag); - return; - } - list_del_init(&rq->queuelist); rq->cmd_flags &= ~REQ_QUEUED; rq->tag = -1; @@ -1090,6 +1084,19 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq) __FUNCTION__, tag); bqt->tag_index[tag] = NULL; + + /* + * We use test_and_clear_bit's memory ordering properties here. + * The tag_map bit acts as a lock for tag_index[bit], so we need + * a barrer before clearing the bit (precisely: release semantics). + * Could use clear_bit_unlock when it is merged. + */ + if (unlikely(!test_and_clear_bit(tag, bqt->tag_map))) { + printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", + __FUNCTION__, tag); + return; + } + bqt->busy--; } @@ -1136,6 +1143,10 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) return 1; } while (test_and_set_bit(tag, bqt->tag_map)); + /* + * We rely on test_and_set_bit providing lock memory ordering semantics + * (could use test_and_set_bit_lock when it is merged). + */ rq->cmd_flags |= REQ_QUEUED; rq->tag = tag; |