Block layer will allocate a spinlock for the queue if the driver does
not provide one in blk_init_queue().
The reason to use the internal spinlock is that blk_cleanup_queue() will
switch to use the internal spinlock in the cleanup code path.
if (q->queue_lock != &q->__queue_lock)
q->queue_lock = &q->__queue_lock;
However, processes which are in D state might have taken the driver
provided spinlock, when the processes wake up, they would release the
block provided spinlock.
=====================================
[ BUG: bad unlock balance detected! ]
3.4.0-rc7+ #238 Not tainted
-------------------------------------
fio/3587 is trying to release lock (&(&q->__queue_lock)->rlock) at:
[<ffffffff813274d2>] blk_queue_bio+0x2a2/0x380
but there are no more locks to release!
other info that might help us debug this:
1 lock held by fio/3587:
#0: (&(&vblk->lock)->rlock){......}, at:
[<ffffffff8132661a>] get_request_wait+0x19a/0x250
Other drivers use block layer provided spinlock as well, e.g. SCSI.
Switching to the block layer provided spinlock saves a bit of memory and
does not increase lock contention. Performance test shows no real
difference is observed before and after this patch.
Changes in v2: Improve commit log as Michael suggested.
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Asias He <asias@xxxxxxxxxx>
---
drivers/block/virtio_blk.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b4fa2d7..774c31d 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -21,8 +21,6 @@ struct workqueue_struct *virtblk_wq;
struct virtio_blk
{
- spinlock_t lock;
-
struct virtio_device *vdev;
struct virtqueue *vq;
@@ -65,7 +63,7 @@ static void blk_done(struct virtqueue *vq)
unsigned int len;
unsigned long flags;
- spin_lock_irqsave(&vblk->lock, flags);
+ spin_lock_irqsave(vblk->disk->queue->queue_lock, flags);
while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
int error;
@@ -99,7 +97,7 @@ static void blk_done(struct virtqueue *vq)
}
/* In case queue is stopped waiting for more buffers. */
blk_start_queue(vblk->disk->queue);
- spin_unlock_irqrestore(&vblk->lock, flags);
+ spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags);
}
static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
@@ -431,7 +429,6 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
goto out_free_index;
}
- spin_lock_init(&vblk->lock);
vblk->vdev = vdev;
vblk->sg_elems = sg_elems;
sg_init_table(vblk->sg, vblk->sg_elems);
@@ -456,7 +453,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
goto out_mempool;
}
- q = vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
+ q = vblk->disk->queue = blk_init_queue(do_virtblk_request, NULL);
if (!q) {
err = -ENOMEM;
goto out_put_disk;
--
1.7.10.2
--
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