[dpdk-dev] [PATCH] vhost: fix race condition in fdset_add
Maxime Coquelin
maxime.coquelin at redhat.com
Tue Dec 11 19:11:02 CET 2018
Hi Matthias,
On 12/6/18 5:00 PM, Matthias Gatto wrote:
> 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 at 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);
Any reason we cannot use the existing fd_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,
>
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