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authorMing Lei <tom.leiming@gmail.com>2014-05-16 23:31:21 +0800
committerShow Liu <show.liu@linaro.org>2014-06-18 12:05:23 +0800
commit2dc8888707c94fc10551a6f8029315be0c1eb3ba (patch)
treebcb178a214afc483285657e6daf8579246c3ddd5
parentcfcf1b140307f01dfb7f95c4879263c307b10ba1 (diff)
downloadlinaro-lsk-2dc8888707c94fc10551a6f8029315be0c1eb3ba.tar.gz
virtio_blk: fix race between start and stop queue
commit aa0818c6ee8d8e4772725a43550823347bc1ad30 upstream. When there isn't enough vring descriptor for adding to vq, blk-mq will be put as stopped state until some of pending descriptors are completed & freed. Unfortunately, the vq's interrupt may come just before blk-mq's BLK_MQ_S_STOPPED flag is set, so the blk-mq will still be kept as stopped even though lots of descriptors are completed and freed in the interrupt handler. The worst case is that all pending descriptors are freed in the interrupt handler, and the queue is kept as stopped forever. This patch fixes the problem by starting/stopping blk-mq with holding vq_lock. Cc: Jens Axboe <axboe@kernel.dk> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/block/virtio_blk.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b1cb3f4c4db..6c911c86fb5 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -144,11 +144,11 @@ static void virtblk_done(struct virtqueue *vq)
if (unlikely(virtqueue_is_broken(vq)))
break;
} while (!virtqueue_enable_cb(vq));
- spin_unlock_irqrestore(&vblk->vq_lock, flags);
/* In case queue is stopped waiting for more buffers. */
if (req_done)
blk_mq_start_stopped_hw_queues(vblk->disk->queue);
+ spin_unlock_irqrestore(&vblk->vq_lock, flags);
}
static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
@@ -200,8 +200,8 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
spin_lock_irqsave(&vblk->vq_lock, flags);
if (__virtblk_add_req(vblk->vq, vbr, vbr->sg, num) < 0) {
virtqueue_kick(vblk->vq);
- spin_unlock_irqrestore(&vblk->vq_lock, flags);
blk_mq_stop_hw_queue(hctx);
+ spin_unlock_irqrestore(&vblk->vq_lock, flags);
return BLK_MQ_RQ_QUEUE_BUSY;
}