netdev - Re: linux-next: zillions of lockdep whinges in include/net/sock.h:1408

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Date:	Thu, 21 Apr 2016 06:31:36 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Valdis.Kletnieks@...edu
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: linux-next: zillions of lockdep whinges in
 include/net/sock.h:1408

On Thu, 2016-04-21 at 05:05 -0400, Valdis.Kletnieks@...edu wrote:
> On Thu, 21 Apr 2016 09:42:12 +0200, Hannes Frederic Sowa said:
> > Hi,
> >
> > On Thu, Apr 21, 2016, at 02:30, Valdis Kletnieks wrote:
> > > linux-next 20160420 is whining at an incredible rate - in 20 minutes of
> > > uptime, I piled up some 41,000 hits from all over the place (cleaned up
> > > to skip the CPU and PID so the list isn't quite so long):
> >
> > Thanks for the report. Can you give me some more details:
> >
> > Is this an nfs socket? Do you by accident know if this socket went
> > through xs_reclassify_socket at any point? We do hold the appropriate
> > locks at that point but I fear that the lockdep reinitialization
> > confused lockdep.
> 
> It wasn't an NFS socket, as NFS wasn't even active at the time.  I'm reasonably
> sure that multiple sockets were in play, given that tcp_v6_rcv and
> udpv6_queue_rcv_skb were both implicated.  I strongly suspect that pretty much
> any IPv6 traffic could do it - the frequency dropped off quite a bit when I
> closed firefox, which is usually a heavy network hitter on my laptop.


Looks like the following patch is needed, can you try it please ?

Thanks !

diff --git a/include/net/sock.h b/include/net/sock.h
index d997ec13a643..db8301c76d50 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1350,7 +1350,8 @@ static inline bool lockdep_sock_is_held(const struct sock *csk)
 {
 	struct sock *sk = (struct sock *)csk;
 
-	return lockdep_is_held(&sk->sk_lock) ||
+	return !debug_locks ||
+	       lockdep_is_held(&sk->sk_lock) ||
 	       lockdep_is_held(&sk->sk_lock.slock);
 }
 #endif