From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757418AbaEPPbx (ORCPT ); Fri, 16 May 2014 11:31:53 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:63302 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756241AbaEPPbw (ORCPT ); Fri, 16 May 2014 11:31:52 -0400 From: Ming Lei To: Jens Axboe , linux-kernel@vger.kernel.org Cc: Ming Lei , Rusty Russell Subject: [PATCH v1] virtio_blk: fix race between start and stop queue Date: Fri, 16 May 2014 23:31:21 +0800 Message-Id: <1400254281-11294-1-git-send-email-tom.leiming@gmail.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: Rusty Russell Signed-off-by: Ming Lei --- v1: - remove 'queue_stopped' flag drivers/block/virtio_blk.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 7a51f06..9f340fa 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -147,11 +147,11 @@ 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, true); + spin_unlock_irqrestore(&vblk->vq_lock, flags); } static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req) @@ -205,8 +205,8 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req) err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num); if (err) { virtqueue_kick(vblk->vq); - spin_unlock_irqrestore(&vblk->vq_lock, flags); blk_mq_stop_hw_queue(hctx); + spin_unlock_irqrestore(&vblk->vq_lock, flags); /* Out of mem doesn't actually happen, since we fall back * to direct descriptors */ if (err == -ENOMEM || err == -ENOSPC) -- 1.7.9.5