net/9p/virtio: Fix hard lockup in req_done (31934da8) · Commits · 戴 / test

When client has multiple threads that issue io requests all the time, and the server has a very good performance, it may cause cpu is running in the irq context for a long time because it can check virtqueue has buf in the *while* loop. So we should keep chan->lock in the whole loop. [ Dominique: reworded subject line ] Link: http://lkml.kernel.org/r/5B503AEC.5080404@huawei.com Signed-off-by:

Yiwen Jiang <jiangyiwen@huawei.com> To: Andrew Morton <akpm@linux-foundation.org> To: Eric Van Hensbergen <ericvh@gmail.com> To: Ron Minnich <rminnich@sandia.gov> To: Latchesar Ionkov <lucho@ionkov.net> Signed-off-by:

Dominique Martinet <dominique.martinet@cea.fr>

net/9p/trans_virtio.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -144,24 +144,25 @@ static void req_done(struct virtqueue *vq)
		struct virtio_chan *chan = vq->vdev->priv;
		unsigned int len;
		struct p9_req_t *req;
		bool need_wakeup = false;
		unsigned long flags;

		p9_debug(P9_DEBUG_TRANS, ": request done\n");

		while (1) {
		spin_lock_irqsave(&chan->lock, flags);
		req = virtqueue_get_buf(chan->vq, &len);
		if (req == NULL) {
		spin_unlock_irqrestore(&chan->lock, flags);
		break;
		}
		while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
		if (!chan->ring_bufs_avail) {
		chan->ring_bufs_avail = 1;
		spin_unlock_irqrestore(&chan->lock, flags);
		/* Wakeup if anyone waiting for VirtIO ring space. */
		wake_up(chan->vc_wq);
		need_wakeup = true;
		}

		if (len)
		p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
		}
		spin_unlock_irqrestore(&chan->lock, flags);
		/* Wakeup if anyone waiting for VirtIO ring space. */
		if (need_wakeup)
		wake_up(chan->vc_wq);
		}

		/**

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