> -----Original Message-----
> From: Burakov, Anatoly
> Sent: Wednesday, June 27, 2018 5:44 PM
> To: dev@dpdk.org
> Cc: Zhang, Qi Z <qi.z.zh...@intel.com>; sta...@dpdk.org
> Subject: [PATCH] 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: sta...@dpdk.org
>
> Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com>
Tested-by: Qi Zhang <qi.z.zh...@intel.com>
Thanks for the quick fix!
Qi
> ---
>
> Notes:
> This patch is needed for multiprocess hotplug support [1], to avoid cases
> where multiple requests deadlock while in progress.
>
> [1] http://patches.dpdk.org/project/dpdk/list/?series=252
>
> 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
