NO, it is different issue.
The current deadlock mentioned in this patch is caused by some blocking
function (like ovsrcu_synchronize) in application (like OVS).
In this patch, the application is needed to break the logical deadlock.
At 2020-04-27 16:09:31, "Maxime Coquelin" <maxime.coque...@redhat.com> wrote:
>
>
>On 3/18/20 4:31 AM, 王志克 wrote:
>> Involve openvswitch group since this fix is highly coupled with OVS.
>> welcome comment.
>> At 2020-03-12 17:57:19, "Zhike Wang" <wangzh...@jd.com> wrote:
>>> The vhost_user_read_cb() and rte_vhost_driver_unregister()
>>> can be called at the same time by 2 threads, and may lead to deadlock.
>>> Eg thread1 calls
>>> vhost_user_read_cb()->vhost_user_get_vring_base()->destroy_device(),
>>> then thread2 calls rte_vhost_driver_unregister(), and will retry the
>>> fdset_try_del() in loop.
>>>
>>> Some application implements destroy_device() as a blocking function, eg
>>> OVS calls ovsrcu_synchronize() insides destroy_device(). As a result,
>>> thread1(eg vhost_events) is blocked to wait quiesce of thread2(eg
>>> ovs-vswitchd),
>>> and thread2 is in a loop to wait thread1 to give up the use of the vhost fd,
>>> then leads to deadlock.
>>>
>>> It is better to return -EAGAIN to application, who will decide how to handle
>>> (eg OVS can call ovsrcu_quiesce() and then retry).
>>>
>>> Signed-off-by: Zhike Wang <wangzh...@jd.com>
>>> ---
>>> lib/librte_vhost/rte_vhost.h | 4 +++-
>>> lib/librte_vhost/socket.c | 8 ++++----
>>> 2 files changed, 7 insertions(+), 5 deletions(-)
>
>
>Isn't it fixed with below commit that landed into DPDK v20.02?
>
>commit 5efb18e85f7fdb436d3e56591656051c16802066
>Author: Maxime Coquelin <maxime.coque...@redhat.com>
>Date: Tue Jan 14 19:53:57 2020 +0100
>
> vhost: fix deadlock on port deletion
>
> If the vhost-user application (e.g. OVS) deletes the vhost-user
> port while Qemu sends a vhost-user request, a deadlock can
> happen if the request handler tries to acquire vhost-user's
> global mutex, which is also locked by the vhost-user port
> deletion API (rte_vhost_driver_unregister).
>
> This patch prevents the deadlock by making
> rte_vhost_driver_unregister() to release the mutex and try
> again if a request is being handled to give a chance to
> the request handler to complete.
>
> Fixes: 8b4b949144b8 ("vhost: fix dead lock on closing in server mode")
> Fixes: 5fbb3941da9f ("vhost: introduce driver features related APIs")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
> Reviewed-by: Tiwei Bie <tiwei....@intel.com>
> Acked-by: Eelco Chaudron <echau...@redhat.com>
>
>>> diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
>>> index c7b619a..276db11 100644
>>> --- a/lib/librte_vhost/rte_vhost.h
>>> +++ b/lib/librte_vhost/rte_vhost.h
>>> @@ -389,7 +389,9 @@ void rte_vhost_log_used_vring(int vid, uint16_t
>>> vring_idx,
>>> */
>>> int rte_vhost_driver_register(const char *path, uint64_t flags);
>>>
>>> -/* Unregister vhost driver. This is only meaningful to vhost user. */
>>> +/* Unregister vhost driver. This is only meaningful to vhost user.
>>> + * Return -EAGAIN if device is busy, and leave it to be handled by
>>> application.
>>> + */
>>> int rte_vhost_driver_unregister(const char *path);
>>>
>>> /**
>>> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
>>> index 7c80121..a75a3f6 100644
>>> --- a/lib/librte_vhost/socket.c
>>> +++ b/lib/librte_vhost/socket.c
>>> @@ -1027,7 +1027,8 @@ struct vhost_user_reconnect_list {
>>> }
>>>
>>> /**
>>> - * Unregister the specified vhost socket
>>> + * Unregister the specified vhost socket.
>>> + * Return -EAGAIN if device is busy, and leave it to be handled by
>>> application.
>>> */
>>> int
>>> rte_vhost_driver_unregister(const char *path)
>>> @@ -1039,7 +1040,6 @@ struct vhost_user_reconnect_list {
>>> if (path == NULL)
>>> return -1;
>>>
>>> -again:
>>> pthread_mutex_lock(&vhost_user.mutex);
>>>
>>> for (i = 0; i < vhost_user.vsocket_cnt; i++) {
>>> @@ -1063,7 +1063,7 @@ struct vhost_user_reconnect_list {
>>> pthread_mutex_unlock(
>>> &vsocket->conn_mutex);
>>> pthread_mutex_unlock(&vhost_user.mutex);
>>> - goto again;
>>> + return -EAGAIN;
>>> }
>>>
>>> VHOST_LOG_CONFIG(INFO,
>>> @@ -1085,7 +1085,7 @@ struct vhost_user_reconnect_list {
>>> if (fdset_try_del(&vhost_user.fdset,
>>> vsocket->socket_fd) == -1) {
>>> pthread_mutex_unlock(&vhost_user.mutex);
>>> - goto again;
>>> + return -EAGAIN;
>>> }
>>>
>>> close(vsocket->socket_fd);
>>> --
>>> 1.8.3.1
>>>
>> _______________________________________________
>> dev mailing list
>> d...@openvswitch.org
>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>>
