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>
---
lib/librte_vhost/socket.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index 633c2cbc27..c57a0c7cdd 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -1052,9 +1052,10 @@ rte_vhost_driver_unregister(const char *path)
next = TAILQ_NEXT(conn, next);
/*
- * If r/wcb is executing, release the
- * conn_mutex lock, and try again since
- * the r/wcb may use the conn_mutex lock.
+ * If r/wcb is executing, release vsocket's
+ * conn_mutex and vhost_user's mutex locks, and
+ * try again since the r/wcb may use the
+ * conn_mutex and mutex locks.
*/
if (fdset_try_del(&vhost_user.fdset,
conn->connfd) == -1) {
@@ -1075,8 +1076,17 @@ rte_vhost_driver_unregister(const char *path)
pthread_mutex_unlock(&vsocket->conn_mutex);
if (vsocket->is_server) {
- fdset_del(&vhost_user.fdset,
- vsocket->socket_fd);
+ /*
+ * If r/wcb is executing, release vhost_user's
+ * mutex lock, and try again since the r/wcb
+ * may use the mutex lock.
+ */
+ if (fdset_try_del(&vhost_user.fdset,
+ vsocket->socket_fd) == -1) {
+ pthread_mutex_unlock(&vhost_user.mutex);
+ goto again;
+ }
+
close(vsocket->socket_fd);
unlink(path);
} else if (vsocket->reconnect) {
--
2.21.0
