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. Signed-off-by: Yiwen Jiang <[email protected]> --- 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 05006cb..3589864 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); } /** -- 1.8.3.1
