[PATCH v2] net: Destroy previously created kthreads after failing to set napi threaded mode

[Zqiang]

When setting 1 to enable napi threaded mode, will traverse dev->napi_list
and create kthread for napi->thread, if creation fails, the dev->threaded
will be set to false and we will clear NAPI_STATE_THREADED bit for all
napi->state in dev->napi_list, even if some napi that has successfully
created the kthread before. as a result, for successfully created napi
kthread, they will never be used.

This commit therefore destroy previously created napi->thread if setting
napi threaded mode fails.

Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
---
 v1->v2:
 Set napi->thread pointer is NULL.

 net/core/dev.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 69a3e544676c..6125a1b1e019 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6317,10 +6317,15 @@ int dev_set_threaded(struct net_device *dev, bool threaded)
 	 * This should not cause hiccups/stalls to the live traffic.
 	 */
 	list_for_each_entry(napi, &dev->napi_list, dev_list) {
-		if (threaded)
+		if (threaded) {
 			set_bit(NAPI_STATE_THREADED, &napi->state);
-		else
+		} else {
 			clear_bit(NAPI_STATE_THREADED, &napi->state);
+			if (napi->thread) {
+				kthread_stop(napi->thread);
+				napi->thread = NULL;
+			}
+		}
 	}
 
 	return err;
-- 
2.17.1