linux-kernel - [PATCH 4.4 032/241] net: avoid weird emergency message

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Message-Id: <20190609164148.706912634@linuxfoundation.org>
Date:   Sun,  9 Jun 2019 18:39:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        syzbot <syzkaller@...glegroups.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 032/241] net: avoid weird emergency message

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

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6986,7 +6986,7 @@ 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;