vhostuser: fix deadlock when vhost unregister

  When rte_vhost_driver_unregister  delete the connection fd, fdset_try_del will
 always try and donot release the  vhostuser.mutex if the fd is busy, but the
 fdset_event_dispatch will set the  fd to busy and call vhost_user_msg_handler
 to get vhostuser.mutex, which will  cause deadlock.

To fix it:
    Unlock the vhost_user.mutex if fdset_try_del fail and relock it when
    retry.
---
 lib/librte_vhost/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
  

Hi Sunwenjie,

Thanks for your patch.

Please resend with following contribution guidelines, that can be
found in doc/guides/contributing/.

First, the commit message prefix should be vhost.
For other comments, please see inline:


On 1/8/19 12:45 PM, sunwenjie wrote:
>   When rte_vhost_driver_unregister  delete the connection fd, fdset_try_del will
>   always try and donot release the  vhostuser.mutex if the fd is busy, but the
>   fdset_event_dispatch will set the  fd to busy and call vhost_user_msg_handler
>   to get vhostuser.mutex, which will  cause deadlock.
> 

The commit message should not be indented, and wrapped at 72 chars.

> To fix it:
>      Unlock the vhost_user.mutex if fdset_try_del fail and relock it when
>      retry.

You need to add your Sined-off-by with your full name.

> ---
>   lib/librte_vhost/socket.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
> index 9cf34ad17..a9effa115 100644
> --- a/lib/librte_vhost/socket.c
> +++ b/lib/librte_vhost/socket.c
> @@ -961,13 +961,12 @@ rte_vhost_driver_unregister(const char *path)
>   	int count;
>   	struct vhost_user_connection *conn, *next;
>   
> +again:
>   	pthread_mutex_lock(&vhost_user.mutex);
>   
>   	for (i = 0; i < vhost_user.vsocket_cnt; i++) {
>   		struct vhost_user_socket *vsocket = vhost_user.vsockets[i];
> -

Keep this new line, it is out of the scope of the change.

>   		if (!strcmp(vsocket->path, path)) {
> -again:
>   			pthread_mutex_lock(&vsocket->conn_mutex);
>   			for (conn = TAILQ_FIRST(&vsocket->conn_list);
>   			     conn != NULL;
> @@ -981,6 +980,7 @@ rte_vhost_driver_unregister(const char *path)
>   				 */
>   				if (fdset_try_del(&vhost_user.fdset,
>   						  conn->connfd) == -1) {
> +					pthread_mutex_unlock(&vhost_user.mutex);
>   					pthread_mutex_unlock(
>   							&vsocket->conn_mutex);
>   					goto again;
> 

Thanks,
Maxime
  

Will do, thanks!

Maxime Coquelin <maxime.coquelin@redhat.com> 于2019年1月10日周四 下午10:48写道：

> Hi Sunwenjie,
>
> Thanks for your patch.
>
> Please resend with following contribution guidelines, that can be
> found in doc/guides/contributing/.
>
> First, the commit message prefix should be vhost.
> For other comments, please see inline:
>
>
> On 1/8/19 12:45 PM, sunwenjie wrote:
> >   When rte_vhost_driver_unregister  delete the connection fd,
> fdset_try_del will
> >   always try and donot release the  vhostuser.mutex if the fd is busy,
> but the
> >   fdset_event_dispatch will set the  fd to busy and call
> vhost_user_msg_handler
> >   to get vhostuser.mutex, which will  cause deadlock.
> >
>
> The commit message should not be indented, and wrapped at 72 chars.
>
> > To fix it:
> >      Unlock the vhost_user.mutex if fdset_try_del fail and relock it when
> >      retry.
>
> You need to add your Sined-off-by with your full name.
>
> > ---
> >   lib/librte_vhost/socket.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
> > index 9cf34ad17..a9effa115 100644
> > --- a/lib/librte_vhost/socket.c
> > +++ b/lib/librte_vhost/socket.c
> > @@ -961,13 +961,12 @@ rte_vhost_driver_unregister(const char *path)
> >       int count;
> >       struct vhost_user_connection *conn, *next;
> >
> > +again:
> >       pthread_mutex_lock(&vhost_user.mutex);
> >
> >       for (i = 0; i < vhost_user.vsocket_cnt; i++) {
> >               struct vhost_user_socket *vsocket = vhost_user.vsockets[i];
> > -
>
> Keep this new line, it is out of the scope of the change.
>
> >               if (!strcmp(vsocket->path, path)) {
> > -again:
> >                       pthread_mutex_lock(&vsocket->conn_mutex);
> >                       for (conn = TAILQ_FIRST(&vsocket->conn_list);
> >                            conn != NULL;
> > @@ -981,6 +980,7 @@ rte_vhost_driver_unregister(const char *path)
> >                                */
> >                               if (fdset_try_del(&vhost_user.fdset,
> >                                                 conn->connfd) == -1) {
> > +
>  pthread_mutex_unlock(&vhost_user.mutex);
> >                                       pthread_mutex_unlock(
> >
>  &vsocket->conn_mutex);
> >                                       goto again;
> >
>
> Thanks,
> Maxime
>