[dpdk-dev] [PATCH v3 4/5] eal: prevent secondary process init while sending messages

[Anatoly Burakov <anatoly.burakov@intel.com>]

Currently, it is possible to spin up a secondary process while
either sendmsg or request is in progress. Fix this by adding
directory locks during init, sendmsg and requests.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---

Notes:
    v3: no changes
    
    v2: no changes

 lib/librte_eal/common/eal_common_proc.c | 47 ++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
index 7c87971..7856a7b 100644
--- a/lib/librte_eal/common/eal_common_proc.c
+++ b/lib/librte_eal/common/eal_common_proc.c
@@ -507,6 +507,7 @@ rte_mp_channel_init(void)
 {
 	char thread_name[RTE_MAX_THREAD_NAME_LEN];
 	char *path;
+	int dir_fd;
 	pthread_t tid;
 
 	snprintf(mp_filter, PATH_MAX, ".%s_unix_*",
@@ -516,14 +517,32 @@ rte_mp_channel_init(void)
 	snprintf(mp_dir_path, PATH_MAX, "%s", dirname(path));
 	free(path);
 
+	/* lock the directory */
+	dir_fd = open(mp_dir_path, O_RDONLY);
+	if (dir_fd < 0) {
+		RTE_LOG(ERR, EAL, "failed to open %s: %s\n",
+			mp_dir_path, strerror(errno));
+		return -1;
+	}
+
+	if (flock(dir_fd, LOCK_EX)) {
+		RTE_LOG(ERR, EAL, "failed to lock %s: %s\n",
+			mp_dir_path, strerror(errno));
+		close(dir_fd);
+		return -1;
+	}
+
 	if (rte_eal_process_type() == RTE_PROC_PRIMARY &&
 	    unlink_sockets(mp_filter)) {
 		RTE_LOG(ERR, EAL, "failed to unlink mp sockets\n");
+		close(dir_fd);
 		return -1;
 	}
 
-	if (open_socket_fd() < 0)
+	if (open_socket_fd() < 0) {
+		close(dir_fd);
 		return -1;
+	}
 
 	if (pthread_create(&tid, NULL, mp_handle, NULL) < 0) {
 		RTE_LOG(ERR, EAL, "failed to create mp thead: %s\n",
@@ -536,6 +555,11 @@ rte_mp_channel_init(void)
 	/* try best to set thread name */
 	snprintf(thread_name, RTE_MAX_THREAD_NAME_LEN, "rte_mp_handle");
 	rte_thread_setname(tid, thread_name);
+
+	/* unlock the directory */
+	flock(dir_fd, LOCK_UN);
+	close(dir_fd);
+
 	return 0;
 }
 
@@ -650,6 +674,14 @@ mp_send(struct rte_mp_msg *msg, const char *peer, int type)
 		return -1;
 	}
 	dir_fd = dirfd(mp_dir);
+	/* lock the directory to prevent processes spinning up while we send */
+	if (flock(dir_fd, LOCK_EX)) {
+		RTE_LOG(ERR, EAL, "Unable to lock directory %s\n",
+			mp_dir_path);
+		rte_errno = errno;
+		closedir(mp_dir);
+		return -1;
+	}
 	while ((ent = readdir(mp_dir))) {
 		char path[PATH_MAX];
 		const char *peer_name;
@@ -673,6 +705,8 @@ mp_send(struct rte_mp_msg *msg, const char *peer, int type)
 		else if (active > 0 && send_msg(path, msg, type) < 0)
 			ret = -1;
 	}
+	/* unlock the dir */
+	flock(dir_fd, LOCK_UN);
 
 	closedir(mp_dir);
 	return ret;
@@ -832,6 +866,15 @@ rte_mp_request(struct rte_mp_msg *req, struct rte_mp_reply *reply,
 	}
 	dir_fd = dirfd(mp_dir);
 
+	/* lock the directory to prevent processes spinning up while we send */
+	if (flock(dir_fd, LOCK_EX)) {
+		RTE_LOG(ERR, EAL, "Unable to lock directory %s\n",
+			mp_dir_path);
+		closedir(mp_dir);
+		rte_errno = errno;
+		return -1;
+	}
+
 	while ((ent = readdir(mp_dir))) {
 		const char *peer_name;
 		char path[PATH_MAX];
@@ -857,6 +900,8 @@ rte_mp_request(struct rte_mp_msg *req, struct rte_mp_reply *reply,
 		if (mp_request_one(path, req, reply, &end))
 			ret = -1;
 	}
+	/* unlock the directory */
+	flock(dir_fd, LOCK_UN);
 
 	closedir(mp_dir);
 	return ret;
-- 
2.7.4