Discussion:
[dpdk-dev] [PATCH] vhost: fix race condition in fdset_add
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Matthias Gatto
2018-12-06 16:00:07 UTC
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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 <***@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
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