[dpdk-dev] [PATCH] lib/librte_vhost: fix vid allocation race

[Peng He]

From: "chenwei.0515" <chenwei.0...@bytedance.com>

vhost_new_devcie might be called in different threads at the same time.
thread 1(config thread)
            rte_vhost_driver_start
               ->vhost_user_start_client
                   ->vhost_user_add_connection
                     -> vhost_new_device

thread 2(vhost-events)
        vhost_user_read_cb
           ->vhost_user_msg_handler (return value < 0)
             -> vhost_user_start_client
                 -> vhost_new_device

So there could be a case that a same vid has been allocated twice, or
some vid might be lost in DPDK lib however still held by the upper
applications.

Reported-by: Peng He <hepeng.0...@bytedance.com>
Signed-off-by: Fei Chen <chenwei.0...@bytedance.com>
Reviewed-by: Zhihong Wang <wangzhihong....@bytedance.com>
---
 lib/librte_vhost/vhost.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index efb136edd1..db11d293d2 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -26,6 +26,7 @@
 #include "vhost_user.h"
 
 struct virtio_net *vhost_devices[MAX_VHOST_DEVICE];
+pthread_mutex_t  vhost_dev_lock = PTHREAD_MUTEX_INITIALIZER;
 
 /* Called with iotlb_lock read-locked */
 uint64_t
@@ -645,6 +646,7 @@ vhost_new_device(void)
        struct virtio_net *dev;
        int i;
 
+       pthread_mutex_lock(&vhost_dev_lock);
        for (i = 0; i < MAX_VHOST_DEVICE; i++) {
                if (vhost_devices[i] == NULL)
                        break;
@@ -653,6 +655,7 @@ vhost_new_device(void)
        if (i == MAX_VHOST_DEVICE) {
                VHOST_LOG_CONFIG(ERR,
                        "Failed to find a free slot for new device.\n");
+               pthread_mutex_unlock(&vhost_dev_lock);
                return -1;
        }
 
@@ -660,10 +663,13 @@ vhost_new_device(void)
        if (dev == NULL) {
                VHOST_LOG_CONFIG(ERR,
                        "Failed to allocate memory for new dev.\n");
+               pthread_mutex_unlock(&vhost_dev_lock);
                return -1;
        }
 
        vhost_devices[i] = dev;
+       pthread_mutex_unlock(&vhost_dev_lock);
+
        dev->vid = i;
        dev->flags = VIRTIO_DEV_BUILTIN_VIRTIO_NET;
        dev->slave_req_fd = -1;
-- 
2.23.0