[PATCH 5.0 004/139] net: avoid weird emergency message

Greg Kroah-Hartman
2019-05-23T19:20:02Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d7c04b05c9ca14c55309eb139430283a45c4c25f ]

When host is under high stress, it is very possible thread
running netdev_wait_allrefs() returns from msleep(250)
10 seconds late.

This leads to these messages in the syslog :

[...] unregister_netdevice: waiting for syz_tun to become free. Usage count = 0

If the device refcount is zero, the wait is over.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8829,7 +8829,7 @@ static void netdev_wait_allrefs(struct n

refcnt = netdev_refcnt_read(dev);

- if (time_after(jiffies, warning_time + 10 * HZ)) {
+ if (refcnt && time_after(jiffies, warning_time + 10 * HZ)) {
pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
dev->name, refcnt);
warning_time = jiffies;