On 05/22/2012 04:59 AM, Michael S. Tsirkin wrote:
On Mon, May 21, 2012 at 05:08:33PM +0800, Asias He wrote:
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.
Are you saying any driver with its own spinlock is
broken if hotunplugged under stress?
Hi, Michael
I can not say that. It is very hard to find real hardware device to try
this. I tried on qemu with LSI Logic / Symbios Logic 53c895a scsi disk
with hot-unplug. It is completely broken. And IDE does not support
hotplug at all.
Do you see any downside of using 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
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 ba35509..0c2f0e8 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,
@@ -456,7 +454,6 @@ 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);
@@ -481,7 +478,7 @@ 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;
--
1.7.10.1
--
Asias
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