From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH] vhost-net: avoid flush under lock Date: Thu, 15 Jul 2010 15:19:12 +0300 Message-ID: <20100715121912.GA7176@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Cc: "Michael S. Tsirkin" , Sridhar Samudrala , "David S. Miller" , Arnd Bergmann , "Paul E. McKenney" , kvm@vger.kernel.org, virtualization@lists.osdl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org We flush under vq mutex when changing backends. This creates a deadlock as workqueue being flushed needs this lock as well. https://bugzilla.redhat.com/show_bug.cgi?id=612421 Drop the vq mutex before flush: we have the device mutex which is sufficient to prevent another ioctl from touching the vq. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/net.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 28d7786..50df58e6 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -534,11 +534,16 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) rcu_assign_pointer(vq->private_data, sock); vhost_net_enable_vq(n, vq); done: + mutex_unlock(&vq->mutex); + if (oldsock) { vhost_net_flush_vq(n, index); fput(oldsock->file); } + mutex_unlock(&n->dev.mutex); + return 0; + err_vq: mutex_unlock(&vq->mutex); err: -- 1.7.2.rc0.14.g41c1c