net: avoid weird emergency message

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>

diff --git a/net/core/dev.c b/net/core/dev.c
index 108ac8137b9be8bc7041b3e49e09c25eeb891d8f..b6b8505cfb3e2394f74b41b8e01055c697ad384b 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8927,7 +8927,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
 
                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;