linux-kernel - [PATCH 3.10 237/319] net: ratelimit warnings about dst entry refcount underflow or overflow

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Date:   Sun,  5 Feb 2017 20:20:59 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        "David S . Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 237/319] net: ratelimit warnings about dst entry refcount underflow or overflow

From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

commit 8bf4ada2e21378816b28205427ee6b0e1ca4c5f1 upstream.

Kernel generates a lot of warnings when dst entry reference counter
overflows and becomes negative. That bug was seen several times at
machines with outdated 3.10.y kernels. Most like it's already fixed
in upstream. Anyway that flood completely kills machine and makes
further debugging impossible.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 net/core/dst.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/dst.c b/net/core/dst.c
index 1bf6842..582b861 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -283,7 +283,9 @@ void dst_release(struct dst_entry *dst)
 		unsigned short nocache = dst->flags & DST_NOCACHE;
 
 		newrefcnt = atomic_dec_return(&dst->__refcnt);
-		WARN_ON(newrefcnt < 0);
+		if (unlikely(newrefcnt < 0))
+			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
+					     __func__, dst, newrefcnt);
 		if (!newrefcnt && unlikely(nocache))
 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
 	}
-- 
2.8.0.rc2.1.gbe9624a