Re: [dpdk-stable] [PATCH v2 v16.11 LTS] vhost-user: fix deadlock in case of NUMA realloc

[Kevin Traynor <ktraynor@redhat.com>]

On 03/28/2018 08:51 PM, Maxime Coquelin wrote:
> Virtqueue's access lock was recently introduced to protect
> the device against async changes.
> 
> One problem with the v16.11 backport is that in case of NUMA
> reallocation, the device gets stuck because the old access_lock
> gets unlocked instead of its reallocated copy. On the next
> vhost-user message received, the thread keeps spinning on the
> lock, as it will never be unlocked.
> 

Reviewed-by: Kevin Traynor <ktraynor@redhat.com>

> Fixes: ce3b23dc9296 ("vhost: protect active rings from async ring changes")
> 
> Cc: stable@dpdk.org
> 
> Tested-by: Kevin Traynor <ktraynor@redhat.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
> V2: remove debug changes squashed by mistake...
> 
>  lib/librte_vhost/vhost_user.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 80348dbf6..94a48a4b0 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -327,9 +327,11 @@ qva_to_vva(struct virtio_net *dev, uint64_t qva)
>   * This function then converts these to our address space.
>   */
>  static int
> -vhost_user_set_vring_addr(struct virtio_net *dev, struct vhost_vring_addr *addr)
> +vhost_user_set_vring_addr(struct virtio_net **pdev,
> +						  struct vhost_vring_addr *addr)
>  {
>  	struct vhost_virtqueue *vq;
> +	struct virtio_net *dev = *pdev;
>  
>  	if (dev->mem == NULL)
>  		return -1;
> @@ -348,6 +350,8 @@ vhost_user_set_vring_addr(struct virtio_net *dev, struct vhost_vring_addr *addr)
>  	}
>  
>  	dev = numa_realloc(dev, addr->index);
> +	*pdev = dev;
> +
>  	vq = dev->virtqueue[addr->index];
>  
>  	vq->avail = (struct vring_avail *)(uintptr_t)qva_to_vva(dev,
> @@ -1092,7 +1096,7 @@ vhost_user_msg_handler(int vid, int fd)
>  		vhost_user_set_vring_num(dev, &msg.payload.state);
>  		break;
>  	case VHOST_USER_SET_VRING_ADDR:
> -		vhost_user_set_vring_addr(dev, &msg.payload.addr);
> +		vhost_user_set_vring_addr(&dev, &msg.payload.addr);
>  		break;
>  	case VHOST_USER_SET_VRING_BASE:
>  		vhost_user_set_vring_base(dev, &msg.payload.state);
>