[dpdk-dev] [PATCH v3 4/4] vhost: fix async register/unregister deadlock
Maxime Coquelin
maxime.coquelin at redhat.com
Mon Oct 5 16:25:57 CEST 2020
On 9/29/20 11:29 AM, Patrick Fu wrote:
> When async register/unregister function is invoked in certain vhost
> event callbacks (e.g. vring state change), deadlock may occur due to
> recursive spinlock acquire. This patch removes unnecessary spinlock
> from register API and use trylock() primitive in the unregister API
> to avoid deadlock.
I am not convinced it is unnecessary in every cases.
> Fixes: 78639d54563a ("vhost: introduce async enqueue registration API")
>
> Signed-off-by: Patrick Fu <patrick.fu at intel.com>
> ---
> lib/librte_vhost/vhost.c | 13 +++++++------
> lib/librte_vhost/vhost_user.c | 4 ++--
> 2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> index 05b578c2f..ba504a00a 100644
> --- a/lib/librte_vhost/vhost.c
> +++ b/lib/librte_vhost/vhost.c
> @@ -1577,8 +1577,6 @@ int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
> ops->transfer_data == NULL))
> return -1;
>
> - rte_spinlock_lock(&vq->access_lock);
> -
What if a virtqueue is being destroyed while this function is called?
> if (unlikely(vq->async_registered)) {
> VHOST_LOG_CONFIG(ERR,
> "async register failed: channel already registered "
> @@ -1627,8 +1625,6 @@ int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
> vq->async_registered = true;
>
> reg_out:
> - rte_spinlock_unlock(&vq->access_lock);
> -
> return 0;
> }
>
> @@ -1647,10 +1643,15 @@ int rte_vhost_async_channel_unregister(int vid, uint16_t queue_id)
> return ret;
>
> ret = 0;
> - rte_spinlock_lock(&vq->access_lock);
>
> if (!vq->async_registered)
> - goto out;
> + return ret;
> +
> + if (!rte_spinlock_trylock(&vq->access_lock)) {
> + VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "
> + "virt queue busy.\n");
> + return -1;
> + }
>
> if (vq->async_pkts_inflight_n) {
> VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 67d2a2d43..c8d74bde6 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -2043,9 +2043,9 @@ vhost_user_set_vring_enable(struct virtio_net **pdev,
> "set queue enable: %d to qp idx: %d\n",
> enable, index);
>
> - if (!enable && dev->virtqueue[index]->async_registered) {
> + if (enable && dev->virtqueue[index]->async_registered) {
> if (dev->virtqueue[index]->async_pkts_inflight_n) {
> - VHOST_LOG_CONFIG(ERR, "failed to disable vring. "
> + VHOST_LOG_CONFIG(ERR, "failed to enable vring. "
> "async inflight packets must be completed first\n");
> return RTE_VHOST_MSG_RESULT_ERR;
> }
>
More information about the dev
mailing list