Re: [PATCH v2 2/3] vsock/virtio: stop workers during the .remove()

From: Jason Wang <jasowang@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>, netdev@vger.kernel.org
Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Stefan Hajnoczi <stefanha@redhat.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v2 2/3] vsock/virtio: stop workers during the .remove()
Date: Thu, 4 Jul 2019 12:00:11 +0800	[thread overview]
Message-ID: <04b93975-1cce-1e7e-61ad-246601d4216c__38393.1275851623$1562212844$gmane$org@redhat.com> (raw)
In-Reply-To: <20190628123659.139576-3-sgarzare@redhat.com>

On 2019/6/28 下午8:36, Stefano Garzarella wrote:
> Before to call vdev->config->reset(vdev) we need to be sure that
> no one is accessing the device, for this reason, we add new variables
> in the struct virtio_vsock to stop the workers during the .remove().
>
> This patch also add few comments before vdev->config->reset(vdev)
> and vdev->config->del_vqs(vdev).
>
> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>   net/vmw_vsock/virtio_transport.c | 51 +++++++++++++++++++++++++++++++-
>   1 file changed, 50 insertions(+), 1 deletion(-)

This should work. But we may consider to convert the_virtio_vosck to 
socket object and use socket refcnt and destructor in the future instead 
of inventing something new by ourselves.

Thanks

>
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index 7ad510ec12e0..1b44ec6f3f6c 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -38,6 +38,7 @@ struct virtio_vsock {
>   	 * must be accessed with tx_lock held.
>   	 */
>   	struct mutex tx_lock;
> +	bool tx_run;
>   
>   	struct work_struct send_pkt_work;
>   	spinlock_t send_pkt_list_lock;
> @@ -53,6 +54,7 @@ struct virtio_vsock {
>   	 * must be accessed with rx_lock held.
>   	 */
>   	struct mutex rx_lock;
> +	bool rx_run;
>   	int rx_buf_nr;
>   	int rx_buf_max_nr;
>   
> @@ -60,6 +62,7 @@ struct virtio_vsock {
>   	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
>   	 */
>   	struct mutex event_lock;
> +	bool event_run;
>   	struct virtio_vsock_event event_list[8];
>   
>   	u32 guest_cid;
> @@ -94,6 +97,10 @@ static void virtio_transport_loopback_work(struct work_struct *work)
>   	spin_unlock_bh(&vsock->loopback_list_lock);
>   
>   	mutex_lock(&vsock->rx_lock);
> +
> +	if (!vsock->rx_run)
> +		goto out;
> +
>   	while (!list_empty(&pkts)) {
>   		struct virtio_vsock_pkt *pkt;
>   
> @@ -102,6 +109,7 @@ static void virtio_transport_loopback_work(struct work_struct *work)
>   
>   		virtio_transport_recv_pkt(pkt);
>   	}
> +out:
>   	mutex_unlock(&vsock->rx_lock);
>   }
>   
> @@ -130,6 +138,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>   
>   	mutex_lock(&vsock->tx_lock);
>   
> +	if (!vsock->tx_run)
> +		goto out;
> +
>   	vq = vsock->vqs[VSOCK_VQ_TX];
>   
>   	for (;;) {
> @@ -188,6 +199,7 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>   	if (added)
>   		virtqueue_kick(vq);
>   
> +out:
>   	mutex_unlock(&vsock->tx_lock);
>   
>   	if (restart_rx)
> @@ -323,6 +335,10 @@ static void virtio_transport_tx_work(struct work_struct *work)
>   
>   	vq = vsock->vqs[VSOCK_VQ_TX];
>   	mutex_lock(&vsock->tx_lock);
> +
> +	if (!vsock->tx_run)
> +		goto out;
> +
>   	do {
>   		struct virtio_vsock_pkt *pkt;
>   		unsigned int len;
> @@ -333,6 +349,8 @@ static void virtio_transport_tx_work(struct work_struct *work)
>   			added = true;
>   		}
>   	} while (!virtqueue_enable_cb(vq));
> +
> +out:
>   	mutex_unlock(&vsock->tx_lock);
>   
>   	if (added)
> @@ -361,6 +379,9 @@ static void virtio_transport_rx_work(struct work_struct *work)
>   
>   	mutex_lock(&vsock->rx_lock);
>   
> +	if (!vsock->rx_run)
> +		goto out;
> +
>   	do {
>   		virtqueue_disable_cb(vq);
>   		for (;;) {
> @@ -470,6 +491,9 @@ static void virtio_transport_event_work(struct work_struct *work)
>   
>   	mutex_lock(&vsock->event_lock);
>   
> +	if (!vsock->event_run)
> +		goto out;
> +
>   	do {
>   		struct virtio_vsock_event *event;
>   		unsigned int len;
> @@ -484,7 +508,7 @@ static void virtio_transport_event_work(struct work_struct *work)
>   	} while (!virtqueue_enable_cb(vq));
>   
>   	virtqueue_kick(vsock->vqs[VSOCK_VQ_EVENT]);
> -
> +out:
>   	mutex_unlock(&vsock->event_lock);
>   }
>   
> @@ -619,12 +643,18 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>   	INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);
>   	INIT_WORK(&vsock->loopback_work, virtio_transport_loopback_work);
>   
> +	mutex_lock(&vsock->tx_lock);
> +	vsock->tx_run = true;
> +	mutex_unlock(&vsock->tx_lock);
> +
>   	mutex_lock(&vsock->rx_lock);
>   	virtio_vsock_rx_fill(vsock);
> +	vsock->rx_run = true;
>   	mutex_unlock(&vsock->rx_lock);
>   
>   	mutex_lock(&vsock->event_lock);
>   	virtio_vsock_event_fill(vsock);
> +	vsock->event_run = true;
>   	mutex_unlock(&vsock->event_lock);
>   
>   	vdev->priv = vsock;
> @@ -659,6 +689,24 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>   	/* Reset all connected sockets when the device disappear */
>   	vsock_for_each_connected_socket(virtio_vsock_reset_sock);
>   
> +	/* Stop all work handlers to make sure no one is accessing the device,
> +	 * so we can safely call vdev->config->reset().
> +	 */
> +	mutex_lock(&vsock->rx_lock);
> +	vsock->rx_run = false;
> +	mutex_unlock(&vsock->rx_lock);
> +
> +	mutex_lock(&vsock->tx_lock);
> +	vsock->tx_run = false;
> +	mutex_unlock(&vsock->tx_lock);
> +
> +	mutex_lock(&vsock->event_lock);
> +	vsock->event_run = false;
> +	mutex_unlock(&vsock->event_lock);
> +
> +	/* Flush all device writes and interrupts, device will not use any
> +	 * more buffers.
> +	 */
>   	vdev->config->reset(vdev);
>   
>   	mutex_lock(&vsock->rx_lock);
> @@ -689,6 +737,7 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>   	}
>   	spin_unlock_bh(&vsock->loopback_list_lock);
>   
> +	/* Delete virtqueues and flush outstanding callbacks if any */
>   	vdev->config->del_vqs(vdev);
>   
>   	mutex_unlock(&the_virtio_vsock_mutex);
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