Subject: Re: kernel BUG at kernel/timer.c:748!

From: Dave Jones <[email-masked]>
Date: Wed, 19 Sep 2012 17:10:59 -0400

On Sat, Sep 15, 2012 at 11:16:52AM -0700, Yuchung Cheng wrote:
 > On Fri, Sep 14, 2012 at 2:29 PM, Dave Jones <[email-masked]> wrote:
 > > On Wed, Sep 05, 2012 at 11:48:29PM +0300, Julian Anastasov wrote:
 > >
 > >  > > kernel BUG at kernel/timer.c:748!
 > >  > > Call Trace:
 > >  > >  ? lock_sock_nested+0x8d/0xa0
 > >  > >  sk_reset_timer+0x1c/0x30
 > >  > >  ? sock_setsockopt+0x8c/0x960
 > >  > >  inet_csk_reset_keepalive_timer+0x20/0x30
 > >  > >  tcp_set_keepalive+0x3d/0x50
 > >  > >  sock_setsockopt+0x923/0x960
 > >  > >  ? trace_hardirqs_on_caller+0x16/0x1e0
 > >  > >  ? fget_light+0x24c/0x520
 > >  > >  sys_setsockopt+0xc6/0xe0
 > >  > >  system_call_fastpath+0x1a/0x1f
 > >  >
 > >  >      Can this help? In case you see ICMPV6_PKT_TOOBIG...
 > >  >
 > >  > [PATCH] tcp: fix possible socket refcount problem for ipv6
 > >
 > > I just managed to reproduce this bug on rc5 with this patch,
 > > so it doesn't seem to help.
 > Could you post some tcpdump traces?

It's likely that there aren't any packets.  The fuzzer isn't smart
enough (yet) to do anything too clever to the sockets it creates.

More likely is that this is some race where thread A is doing a setsockopt
while thread B is doing a tear-down of the same socket.

	Dave