From 476e8ba712fa6a479192dfc4301cd3765d9ba713 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 13 Dec 2018 10:53:38 +0800 Subject: vhost_net: switch to use mutex_trylock() in vhost_net_busy_poll() We used to hold the mutex of paired virtqueue in vhost_net_busy_poll(). But this will results an inconsistent lock order which may cause deadlock if we try to bring back the protection of device IOTLB with vq mutex that requires to hold mutex of all virtqueues at the same time. Fix this simply by switching to use mutex_trylock(), when fail just skip the busy polling. This can happen when device IOTLB is under updating which should be rare. Fixes: commit 78139c94dc8c ("net: vhost: lock the vqs one by one") Cc: Tonghao Zhang Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/vhost/net.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'drivers/vhost/net.c') diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index ab11b2bee273..ad7a6f475a44 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -513,7 +513,13 @@ static void vhost_net_busy_poll(struct vhost_net *net, struct socket *sock; struct vhost_virtqueue *vq = poll_rx ? tvq : rvq; - mutex_lock_nested(&vq->mutex, poll_rx ? VHOST_NET_VQ_TX: VHOST_NET_VQ_RX); + /* Try to hold the vq mutex of the paired virtqueue. We can't + * use mutex_lock() here since we could not guarantee a + * consistenet lock ordering. + */ + if (!mutex_trylock(&vq->mutex)) + return; + vhost_disable_notify(&net->dev, vq); sock = rvq->private_data; -- cgit v1.2.3-59-g8ed1b