[dpdk-dev] [PATCH] vhost: fix race condition in fdset_add

[Matthias Gatto <matthias.gatto@outscale.com>]

fdset_add can call fdset_shrink_nolock which call fdset_move
concurrently to poll that is call in fdset_event_dispatch.

This patch add a mutex to protect poll from been call at the same time
fdset_add call fdset_shrink_nolock.

Signed-off-by: Matthias Gatto <matthias.gatto@outscale.com>
---
 lib/librte_vhost/fd_man.c | 4 ++++
 lib/librte_vhost/fd_man.h | 1 +
 lib/librte_vhost/socket.c | 1 +
 3 files changed, 6 insertions(+)

diff --git a/lib/librte_vhost/fd_man.c b/lib/librte_vhost/fd_man.c
index 38347ab..55d4856 100644
--- a/lib/librte_vhost/fd_man.c
+++ b/lib/librte_vhost/fd_man.c
@@ -129,7 +129,9 @@
 	pthread_mutex_lock(&pfdset->fd_mutex);
 	i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
 	if (i == -1) {
+		pthread_mutex_lock(&pfdset->fd_pooling_mutex);
 		fdset_shrink_nolock(pfdset);
+		pthread_mutex_unlock(&pfdset->fd_pooling_mutex);
 		i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
 		if (i == -1) {
 			pthread_mutex_unlock(&pfdset->fd_mutex);
@@ -246,7 +248,9 @@
 		numfds = pfdset->num;
 		pthread_mutex_unlock(&pfdset->fd_mutex);
 
+		pthread_mutex_lock(&pfdset->fd_pooling_mutex);
 		val = poll(pfdset->rwfds, numfds, 1000 /* millisecs */);
+		pthread_mutex_unlock(&pfdset->fd_pooling_mutex);
 		if (val < 0)
 			continue;
 
diff --git a/lib/librte_vhost/fd_man.h b/lib/librte_vhost/fd_man.h
index 3331bcd..3ab5cfd 100644
--- a/lib/librte_vhost/fd_man.h
+++ b/lib/librte_vhost/fd_man.h
@@ -24,6 +24,7 @@ struct fdset {
 	struct pollfd rwfds[MAX_FDS];
 	struct fdentry fd[MAX_FDS];
 	pthread_mutex_t fd_mutex;
+	pthread_mutex_t fd_pooling_mutex;
 	int num;	/* current fd number of this fdset */
 
 	union pipefds {
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index d630317..cc4e748 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -88,6 +88,7 @@ struct vhost_user {
 	.fdset = {
 		.fd = { [0 ... MAX_FDS - 1] = {-1, NULL, NULL, NULL, 0} },
 		.fd_mutex = PTHREAD_MUTEX_INITIALIZER,
+		.fd_pooling_mutex = PTHREAD_MUTEX_INITIALIZER,
 		.num = 0
 	},
 	.vsocket_cnt = 0,
-- 
1.8.3.1