diff options
| author | Christoph Hellwig <hch@lst.de> | 2014-04-11 19:07:01 +0200 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2014-07-25 07:43:45 -0400 |
| commit | 71e75c97f97a9645d25fbf3d8e4165a558f18747 (patch) | |
| tree | fb85185386af55199c46499dc3ce366d227870e1 /drivers/scsi/sg.c | |
| parent | 74665016086615bbaa3fa6f83af410a0a4e029ee (diff) | |
scsi: convert device_busy to atomic_t
Avoid taking the queue_lock to check the per-device queue limit. Instead
we do an atomic_inc_return early on to grab our slot in the queue,
and if necessary decrement it after finishing all checks.
Unlike the host and target busy counters this doesn't allow us to avoid the
queue_lock in the request_fn due to the way the interface works, but it'll
allow us to prepare for using the blk-mq code, which doesn't use the
queue_lock at all, and it at least avoids a queue_lock round trip in
scsi_device_unbusy, which is still important given how busy the queue_lock
is.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Webb Scales <webbnh@hp.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Robert Elliott <elliott@hp.com>
Diffstat (limited to 'drivers/scsi/sg.c')
| -rw-r--r-- | drivers/scsi/sg.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 7a291f5c7227..01cf88888797 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -2574,7 +2574,7 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v) scsidp->id, scsidp->lun, (int) scsidp->type, 1, (int) scsidp->queue_depth, - (int) scsidp->device_busy, + (int) atomic_read(&scsidp->device_busy), (int) scsi_device_online(scsidp)); } read_unlock_irqrestore(&sg_index_lock, iflags); |