[dpdk-stable] patch 'ipc: fix locking while sending messages' has been queued to stable release 18.05.1

[Christian Ehrhardt]

Hi,

FYI, your patch has been queued to stable release 18.05.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/01/18. So please
shout if anyone has objections.

Thanks.

Christian Ehrhardt <christian.ehrhardt at canonical.com>

---
>From 27fdec7f7575c83d08c7765916f449676a66f0b3 Mon Sep 17 00:00:00 2001
From: Anatoly Burakov <anatoly.burakov at intel.com>
Date: Wed, 27 Jun 2018 10:44:25 +0100
Subject: [PATCH] ipc: fix locking while sending messages

[ upstream commit 53fd532e3961092b51c536fc6760ad91c6e4bb93 ]

Previously, we were putting an exclusive lock to prevent secondary
processes spinning up while we are sending our messages. However,
using exclusive locks had an effect of disallowing multiple
simultaenous unrelated messages/requests being sent, which was
not the intention behind locking.

Fix it to put a shared lock on the directory. That way, we still
prevent secondary process initializations while sending data over
IPC, but allow multiple unrelated transmissions to proceed.

Fixes: 89f1fe7e6d95 ("eal: lock IPC directory on init and send")

Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
Tested-by: Qi Zhang <qi.z.zhang at intel.com>
---
 lib/librte_eal/common/eal_common_proc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
index 707d8ab30..f010ef59e 100644
--- a/lib/librte_eal/common/eal_common_proc.c
+++ b/lib/librte_eal/common/eal_common_proc.c
@@ -786,7 +786,7 @@ mp_send(struct rte_mp_msg *msg, const char *peer, int type)
 
 	dir_fd = dirfd(mp_dir);
 	/* lock the directory to prevent processes spinning up while we send */
-	if (flock(dir_fd, LOCK_EX)) {
+	if (flock(dir_fd, LOCK_SH)) {
 		RTE_LOG(ERR, EAL, "Unable to lock directory %s\n",
 			mp_dir_path);
 		rte_errno = errno;
@@ -1020,7 +1020,7 @@ rte_mp_request_sync(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)) {
+	if (flock(dir_fd, LOCK_SH)) {
 		RTE_LOG(ERR, EAL, "Unable to lock directory %s\n",
 			mp_dir_path);
 		closedir(mp_dir);
@@ -1146,7 +1146,7 @@ rte_mp_request_async(struct rte_mp_msg *req, const struct timespec *ts,
 	dir_fd = dirfd(mp_dir);
 
 	/* lock the directory to prevent processes spinning up while we send */
-	if (flock(dir_fd, LOCK_EX)) {
+	if (flock(dir_fd, LOCK_SH)) {
 		RTE_LOG(ERR, EAL, "Unable to lock directory %s\n",
 			mp_dir_path);
 		rte_errno = errno;
-- 
2.17.1