diff mbox series

[v1,4/4] vhost: fix async register/unregister deadlock

Message ID 20200911015316.1903181-5-patrick.fu@intel.com (mailing list archive)
State Superseded, archived
Delegated to: Maxime Coquelin
Headers
Series optimize async data path |

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/iol-broadcom-Performance success Performance Testing PASS
ci/iol-broadcom-Functional success Functional Testing PASS
ci/iol-intel-Functional success Functional Testing PASS
ci/iol-intel-Performance success Performance Testing PASS
ci/iol-mellanox-Performance success Performance Testing PASS
ci/travis-robot success Travis build: passed
ci/Intel-compilation success Compilation OK
ci/iol-testing success Testing PASS

Commit Message

Patrick Fu Sept. 11, 2020, 1:53 a.m. UTC 
  When async register/unregister function is invoked in certain vhost
event callbacks (e.g. vring state change), deadlock may occur due to
recursive spinlock acquire. This patch removes unnecessary spinlock
from register API and use trylock() primitive in the unregister API
to avoid deadlock.

Fixes: 78639d54563a ("vhost: introduce async enqueue registration API")

Signed-off-by: Patrick Fu <patrick.fu@intel.com>
---
 lib/librte_vhost/vhost.c      | 13 +++++++------
 lib/librte_vhost/vhost_user.c |  4 ++--
 2 files changed, 9 insertions(+), 8 deletions(-)
diff mbox series

Patch

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index ba374da67..8c2fee6b6 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -1576,8 +1576,6 @@  int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
 		ops->transfer_data == NULL))
 		return -1;
 
-	rte_spinlock_lock(&vq->access_lock);
-
 	if (unlikely(vq->async_registered)) {
 		VHOST_LOG_CONFIG(ERR,
 			"async register failed: channel already registered "
@@ -1615,8 +1613,6 @@  int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
 	vq->async_registered = true;
 
 reg_out:
-	rte_spinlock_unlock(&vq->access_lock);
-
 	return 0;
 }
 
@@ -1635,10 +1631,15 @@  int rte_vhost_async_channel_unregister(int vid, uint16_t queue_id)
 		return ret;
 
 	ret = 0;
-	rte_spinlock_lock(&vq->access_lock);
 
 	if (!vq->async_registered)
-		goto out;
+		return ret;
+
+	if (!rte_spinlock_trylock(&vq->access_lock)) {
+		VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "
+			"virt queue busy.\n");
+		return -1;
+	}
 
 	if (vq->async_pkts_inflight_n) {
 		VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index f6cdbede7..39cd57aeb 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -2043,9 +2043,9 @@  vhost_user_set_vring_enable(struct virtio_net **pdev,
 		"set queue enable: %d to qp idx: %d\n",
 		enable, index);
 
-	if (!enable && dev->virtqueue[index]->async_registered) {
+	if (enable && dev->virtqueue[index]->async_registered) {
 		if (dev->virtqueue[index]->async_pkts_inflight_n) {
-			VHOST_LOG_CONFIG(ERR, "failed to disable vring. "
+			VHOST_LOG_CONFIG(ERR, "failed to enable vring. "
 			"async inflight packets must be completed first\n");
 			return RTE_VHOST_MSG_RESULT_ERR;
 		}