[dpdk-dev] [PATCH] eal/ipc: fix missing mutex unlocks on failed msg send

[dpdk-dev] [PATCH] eal/ipc: fix missing mutex unlocks on failed msg send

[Anatoly Burakov]

Earlier fix for race condition introduced a bug where mutex
wasn't unlocked if message failed to be sent. Fix all of this
by moving locking out of mp_request_sync() altogether.

Fixes: da5957821bdd ("eal: fix race condition in IPC request")
Cc: anatoly.burakov@intel.com

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/common/eal_common_proc.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
index a8ca7b8..2d3bda3 100644
--- a/lib/librte_eal/common/eal_common_proc.c
+++ b/lib/librte_eal/common/eal_common_proc.c
@@ -919,12 +919,10 @@ mp_request_sync(const char *dst, struct rte_mp_msg *req,
 	sync_req.reply = &msg;
 	pthread_cond_init(&sync_req.sync.cond, NULL);
 
-	pthread_mutex_lock(&pending_requests.lock);
 	exist = find_sync_request(dst, req->name);
 	if (exist) {
 		RTE_LOG(ERR, EAL, "A pending request %s:%s\n", dst, req->name);
 		rte_errno = EEXIST;
-		pthread_mutex_unlock(&pending_requests.lock);
 		return -1;
 	}
 
@@ -945,9 +943,7 @@ mp_request_sync(const char *dst, struct rte_mp_msg *req,
 				&pending_requests.lock, ts);
 	} while (ret != 0 && ret != ETIMEDOUT);
 
-	/* We got the lock now */
 	TAILQ_REMOVE(&pending_requests.requests, &sync_req, next);
-	pthread_mutex_unlock(&pending_requests.lock);
 
 	if (sync_req.reply_received == 0) {
 		RTE_LOG(ERR, EAL, "Fail to recv reply for request %s:%s\n",
@@ -1006,8 +1002,12 @@ rte_mp_request_sync(struct rte_mp_msg *req, struct rte_mp_reply *reply,
 	reply->msgs = NULL;
 
 	/* for secondary process, send request to the primary process only */
-	if (rte_eal_process_type() == RTE_PROC_SECONDARY)
-		return mp_request_sync(eal_mp_socket_path(), req, reply, &end);
+	if (rte_eal_process_type() == RTE_PROC_SECONDARY) {
+		pthread_mutex_lock(&pending_requests.lock);
+		ret = mp_request_sync(eal_mp_socket_path(), req, reply, &end);
+		pthread_mutex_unlock(&pending_requests.lock);
+		return ret;
+	}
 
 	/* for primary process, broadcast request, and collect reply 1 by 1 */
 	mp_dir = opendir(mp_dir_path);
@@ -1027,6 +1027,7 @@ rte_mp_request_sync(struct rte_mp_msg *req, struct rte_mp_reply *reply,
 		return -1;
 	}
 
+	pthread_mutex_lock(&pending_requests.lock);
 	while ((ent = readdir(mp_dir))) {
 		char path[PATH_MAX];
 
@@ -1036,9 +1037,13 @@ rte_mp_request_sync(struct rte_mp_msg *req, struct rte_mp_reply *reply,
 		snprintf(path, sizeof(path), "%s/%s", mp_dir_path,
 			 ent->d_name);
 
+		/* unlocks the mutex while waiting for response, locks on
+		 * recieve
+		 */
 		if (mp_request_sync(path, req, reply, &end))
 			ret = -1;
 	}
+	pthread_mutex_unlock(&pending_requests.lock);
 	/* unlock the directory */
 	flock(dir_fd, LOCK_UN);
 
-- 
2.7.4

Re: [dpdk-dev] [PATCH] eal/ipc: fix missing mutex unlocks on failed msg send

[Thomas Monjalon]

13/04/2018 16:16, Anatoly Burakov:
> Earlier fix for race condition introduced a bug where mutex
> wasn't unlocked if message failed to be sent. Fix all of this
> by moving locking out of mp_request_sync() altogether.
> 
> Fixes: da5957821bdd ("eal: fix race condition in IPC request")
> Cc: anatoly.burakov@intel.com
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

Applied, thanks