diff options
author | Nick Piggin <npiggin@suse.de> | 2008-04-29 14:48:33 +0200 |
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committer | Jens Axboe <jens.axboe@oracle.com> | 2008-04-29 14:48:33 +0200 |
commit | 75ad23bc0fcb4f992a5d06982bf0857ab1738e9e (patch) | |
tree | 8668ef63b1f420252ae41aed9e13737d49fd8054 /drivers/scsi/scsi_lib.c | |
parent | block: add dma alignment and padding support to blk_rq_map_kern (diff) | |
download | linux-75ad23bc0fcb4f992a5d06982bf0857ab1738e9e.tar.xz linux-75ad23bc0fcb4f992a5d06982bf0857ab1738e9e.zip |
block: make queue flags non-atomic
We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'drivers/scsi/scsi_lib.c')
-rw-r--r-- | drivers/scsi/scsi_lib.c | 31 |
1 files changed, 18 insertions, 13 deletions
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 67f412bb4974..d545ad1cf47a 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -536,6 +536,9 @@ static void scsi_run_queue(struct request_queue *q) !shost->host_blocked && !shost->host_self_blocked && !((shost->can_queue > 0) && (shost->host_busy >= shost->can_queue))) { + + int flagset; + /* * As long as shost is accepting commands and we have * starved queues, call blk_run_queue. scsi_request_fn @@ -549,19 +552,20 @@ static void scsi_run_queue(struct request_queue *q) sdev = list_entry(shost->starved_list.next, struct scsi_device, starved_entry); list_del_init(&sdev->starved_entry); - spin_unlock_irqrestore(shost->host_lock, flags); - + spin_unlock(shost->host_lock); + + spin_lock(sdev->request_queue->queue_lock); + flagset = test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) && + !test_bit(QUEUE_FLAG_REENTER, + &sdev->request_queue->queue_flags); + if (flagset) + queue_flag_set(QUEUE_FLAG_REENTER, sdev->request_queue); + __blk_run_queue(sdev->request_queue); + if (flagset) + queue_flag_clear(QUEUE_FLAG_REENTER, sdev->request_queue); + spin_unlock(sdev->request_queue->queue_lock); - if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) && - !test_and_set_bit(QUEUE_FLAG_REENTER, - &sdev->request_queue->queue_flags)) { - blk_run_queue(sdev->request_queue); - clear_bit(QUEUE_FLAG_REENTER, - &sdev->request_queue->queue_flags); - } else - blk_run_queue(sdev->request_queue); - - spin_lock_irqsave(shost->host_lock, flags); + spin_lock(shost->host_lock); if (unlikely(!list_empty(&sdev->starved_entry))) /* * sdev lost a race, and was put back on the @@ -1585,8 +1589,9 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost, blk_queue_max_segment_size(q, dma_get_max_seg_size(dev)); + /* New queue, no concurrency on queue_flags */ if (!shost->use_clustering) - clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); + queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q); /* * set a reasonable default alignment on word boundaries: the |