ipc: fix locking while sending messages

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")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Qi Zhang <qi.z.zhang@intel.com>

diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
index 707d8ab..f010ef5 100644 (file)
--- 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;