From 31934da810365f603dec5a67e690e00cf900fc73 Mon Sep 17 00:00:00 2001 From: jiangyiwen Date: Thu, 19 Jul 2018 15:17:00 +0800 Subject: [PATCH] net/9p/virtio: Fix hard lockup in req_done 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 To: Andrew Morton To: Eric Van Hensbergen To: Ron Minnich To: Latchesar Ionkov Signed-off-by: Dominique Martinet --- net/9p/trans_virtio.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index c5464ec311fe..d422bfc81eca 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -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; + spin_lock_irqsave(&chan->lock, flags); + while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) { + if (!chan->ring_bufs_avail) { + chan->ring_bufs_avail = 1; + need_wakeup = true; } - chan->ring_bufs_avail = 1; - spin_unlock_irqrestore(&chan->lock, flags); - /* Wakeup if anyone waiting for VirtIO ring space. */ - wake_up(chan->vc_wq); + 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); } /**