From 4b422cb99836de3d261faec20a0329385bdec43d Mon Sep 17 00:00:00 2001 From: Junxiao Bi Date: Thu, 20 Jul 2017 09:26:21 +0800 Subject: [PATCH] xen-blkfront: fix mq start/stop race MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When ring buf full, hw queue will be stopped. While blkif interrupt consume request and make free space in ring buf, hw queue will be started again. But since start queue is protected by spin lock while stop not, that will cause a race. interrupt: process: blkif_interrupt() blkif_queue_rq() kick_pending_request_queues_locked() blk_mq_start_stopped_hw_queues() clear_bit(BLK_MQ_S_STOPPED, &hctx->state) blk_mq_stop_hw_queue(hctx) blk_mq_run_hw_queue(hctx, async) If ring buf is made empty in this case, interrupt will never come, then the hw queue will be stopped forever, all processes waiting for the pending io in the queue will hung. Signed-off-by: Junxiao Bi Reviewed-by: Ankur Arora Acked-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkfront.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 1799bba74390..04eeb540490f 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -906,8 +906,8 @@ out_err: return BLK_STS_IOERR; out_busy: - spin_unlock_irqrestore(&rinfo->ring_lock, flags); blk_mq_stop_hw_queue(hctx); + spin_unlock_irqrestore(&rinfo->ring_lock, flags); return BLK_STS_RESOURCE; } -- 2.20.1