[PATCH v2] vhost: avoid sleeping under mutex

[David Marchand <david.marchand@redhat.com>]

Covscan reported:

 2. dpdk-21.11/lib/vhost/socket.c:852: lock_acquire: Calling function
	"pthread_mutex_lock" acquires lock "vhost_user.mutex".
23. dpdk-21.11/lib/vhost/socket.c:955: sleep: Call to
	"vhost_user_reconnect_init" might sleep while holding lock
	"vhost_user.mutex".
 #   953|   		vsocket->reconnect =
	!(flags & RTE_VHOST_USER_NO_RECONNECT);
 #   954|   		if (vsocket->reconnect && reconn_tid == 0) {
 #   955|-> 			if (vhost_user_reconnect_init() != 0)
 #   956|   				goto out_mutex;
 #   957|   		}

The reason for this warning is that vhost_user_reconnect_init() creates a
ctrl thread and calls nanosleep waiting for this thread to be ready,
while vhost_user.mutex is taken.

Move the call to vhost_user_reconnect_init() out of this mutex.

While at it, a pthread_t value should be considered opaque.
Instead of relying reconn_tid == 0, use an internal flag in
vhost_user_reconnect_init().

Coverity issue: 373686
Bugzilla ID: 981
Fixes: e623e0c6d8a5 ("vhost: add reconnect ability")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since v1:
- moved reconn_tid in vhost_user_reconnect_init as this
  variable is not used anywhere else,

---
 lib/vhost/socket.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index 669c322e12..00a912c59e 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -427,7 +427,6 @@ struct vhost_user_reconnect_list {
 };
 
 static struct vhost_user_reconnect_list reconn_list;
-static pthread_t reconn_tid;
 
 static int
 vhost_user_connect_nonblock(char *path, int fd, struct sockaddr *un, size_t sz)
@@ -498,8 +497,13 @@ vhost_user_client_reconnect(void *arg __rte_unused)
 static int
 vhost_user_reconnect_init(void)
 {
+	static bool reconn_init_done;
+	static pthread_t reconn_tid;
 	int ret;
 
+	if (reconn_init_done)
+		return 0;
+
 	ret = pthread_mutex_init(&reconn_list.mutex, NULL);
 	if (ret < 0) {
 		VHOST_LOG_CONFIG("thread", ERR, "%s: failed to initialize mutex\n", __func__);
@@ -515,6 +519,8 @@ vhost_user_reconnect_init(void)
 			VHOST_LOG_CONFIG("thread", ERR,
 				"%s: failed to destroy reconnect mutex\n",
 				__func__);
+	} else {
+		reconn_init_done = true;
 	}
 
 	return ret;
@@ -866,6 +872,11 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 	if (!path)
 		return -1;
 
+	if ((flags & RTE_VHOST_USER_CLIENT) != 0 &&
+			(flags & RTE_VHOST_USER_NO_RECONNECT) == 0 &&
+			vhost_user_reconnect_init() != 0)
+		return -1;
+
 	pthread_mutex_lock(&vhost_user.mutex);
 
 	if (vhost_user.vsocket_cnt == MAX_VHOST_SOCKET) {
@@ -961,11 +972,7 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 	}
 
 	if ((flags & RTE_VHOST_USER_CLIENT) != 0) {
-		vsocket->reconnect = !(flags & RTE_VHOST_USER_NO_RECONNECT);
-		if (vsocket->reconnect && reconn_tid == 0) {
-			if (vhost_user_reconnect_init() != 0)
-				goto out_mutex;
-		}
+		vsocket->reconnect = (flags & RTE_VHOST_USER_NO_RECONNECT) == 0;
 	} else {
 		vsocket->is_server = true;
 	}
-- 
2.40.0