netdev - Re: Freeing alive fib_info caused by ebc0ffae5

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Message-ID: <1288867606.2659.72.camel@edumazet-laptop>
Date:	Thu, 04 Nov 2010 11:46:46 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	michael@...erman.id.au
Cc:	netdev@...r.kernel.org
Subject: Re: Freeing alive fib_info caused by ebc0ffae5

Le jeudi 04 novembre 2010 à 11:30 +0100, Eric Dumazet a écrit :
> Le jeudi 04 novembre 2010 à 21:23 +1100, Michael Ellerman a écrit :
> > Hi all,
> > 
> > I'm running Linus' latest or thereabouts (ff8b16d), and I'm seeing
> > "Freeing alive fib_info" messages, from free_fib_info().
> > 
> > Actually I only get one per boot, when network interfaces come up.
> > Seemingly related I am getting refcount problems when I shutdown, ie.
> > unregister_netdevice() sees a usage count of 1, which never decrements.
> > 
> > Bisect says it's ebc0ffae5 which causes the problem, or makes it appear.
> > 
> >     fib: RCU conversion of fib_lookup()
> >     
> >     fib_lookup() converted to be called in RCU protected context, no
> >     reference taken and released on a contended cache line (fib_clntref)
> >     
> > 
> > Is this a bug in that commit, or a driver bug exposed?
> 
> Hi Michael, thanks for the report (and painful bisection I guess)
> 
> Thats hard to say... Is it reproductable on my machine ?

You could ask a stack trace eventually, this might help to spot the bug.

Thanks

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 3e0da3e..8039db0 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -159,6 +159,7 @@ void free_fib_info(struct fib_info *fi)
 {
 	if (fi->fib_dead == 0) {
 		pr_warning("Freeing alive fib_info %p\n", fi);
+		WARN_ON_ONCE(1);
 		return;
 	}
 	change_nexthops(fi) {



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