[dpdk-dev] [PATCH v4 1/4] vhost: call fdset_del_slot to remove connection fd

[Ouyang, Changchun]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Huawei Xie
> Sent: Tuesday, June 30, 2015 5:21 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH v4 1/4] vhost: call fdset_del_slot to remove
> connection fd
> 
> In the event handler of connection fd, the connection fd could be possibly
> closed. The event dispatch loop would then try to remove the fd from fdset.
> Between these two actions, another thread might register a new listenfd
> reusing the val of just closed fd, so we couldn't call fdset_del which would
> wrongly clean up the new listenfd. A new function fdset_del_slot is provided
> to cleanup the fd at the specified location.
> 
> v4 changes:
> - call fdset_del_slot to remove connection fd
> 
> Signed-off-by: Huawei Xie <huawei.xie at intel.com>

Acked-by: Changchun Ouyang <changchun.ouyang at intel.com>

> ---
>  lib/librte_vhost/vhost_user/fd_man.c | 27
> ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_vhost/vhost_user/fd_man.c
> b/lib/librte_vhost/vhost_user/fd_man.c
> index 831c9c1..bd30f8d 100644
> --- a/lib/librte_vhost/vhost_user/fd_man.c
> +++ b/lib/librte_vhost/vhost_user/fd_man.c
> @@ -188,6 +188,24 @@ fdset_del(struct fdset *pfdset, int fd)  }
> 
>  /**
> + *  Unregister the fd at the specified slot from the fdset.
> + */
> +static void
> +fdset_del_slot(struct fdset *pfdset, int index) {
> +	if (pfdset == NULL || index < 0 || index >= MAX_FDS)
> +		return;
> +
> +	pthread_mutex_lock(&pfdset->fd_mutex);
> +
> +	pfdset->fd[index].fd = -1;
> +	pfdset->fd[index].rcb = pfdset->fd[index].wcb = NULL;
> +	pfdset->num--;
> +
> +	pthread_mutex_unlock(&pfdset->fd_mutex);
> +}
> +
> +/**
>   * This functions runs in infinite blocking loop until there is no fd in
>   * pfdset. It calls corresponding r/w handler if there is event on the fd.
>   *
> @@ -248,8 +266,15 @@ fdset_event_dispatch(struct fdset *pfdset)
>  			 * We don't allow fdset_del to be called in callback
>  			 * directly.
>  			 */
> +			/*
> +			 * When we are to clean up the fd from fdset,
> +			 * because the fd is closed in the cb,
> +			 * the old fd val could be reused by when creates
> new
> +			 * listen fd in another thread, we couldn't call
> +			 * fd_set_del.
> +			 */
>  			if (remove1 || remove2)
> -				fdset_del(pfdset, fd);
> +				fdset_del_slot(pfdset, i);
>  		}
>  	}
>  }
> --
> 1.8.1.4