From: Ben Greear <greearb@candelatech•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: David Miller <davem@davemloft•net>,
netdev@vger•kernel.org, gregkh@linuxfoundation•org,
"Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
Subject: Re: RCU lock bug in 3.0.21 (bisected to: 682cb56a, fix NULL dereferences in check_peer_redir)
Date: Mon, 26 Mar 2012 16:46:40 -0700 [thread overview]
Message-ID: <4F70FFE0.7070204@candelatech.com> (raw)
In-Reply-To: <1332805148.3547.14.camel@edumazet-glaptop>
On 03/26/2012 04:39 PM, Eric Dumazet wrote:
> On Mon, 2012-03-26 at 16:06 -0700, Ben Greear wrote:
>> On 03/26/2012 02:53 PM, Ben Greear wrote:
>>> On 03/26/2012 02:49 PM, David Miller wrote:
>>>>
>>>> Looks like all of those strange undiagnosable reported Dave Jones
>>>> has been feeding us. Something in one part of the kernel leaves
>>>> a lock held, and this shows up as a warning elsewhere.
>>>
>>> Every (initial) bug printout fingers ipv6 and the 'ip' tool on my system.
>>
>> I added a patch to convert rcu_read_lock/unlock to macros so
>> that I could automatically grab the call site (_THIS_IP_)
>> and pass it into the lockdep framework instead of the (useless)
>> _THIS_IP_ in the old rcu_read_lock method which at best seems to
>> only indicate which module the issue relates to...
>
> Hi Ben
>
> Is this problem also appears with current tree ?
> (This could be a problem with the backport, as it was full of
> dependencies)
I don't think so..but I will double check in a bit.
> Also, if you use a patch to better track rcu_read_lock()/unlock(), you
> could add new macros as well to track that a particular unlock() matches
> one given lock(). (maybe returning the rcu_preempt_depth at
> rcu_read_lock() time , but maybe a more absolute ref would be better)
>
> So we could have a warning if an unlock() doesnt match the lock()
>
> inet6_dump_fib () was already a suspect but we could not find why.
The 3.0.21 kernel doesn't appear to have a rcu_read_lock_return(),
so I can't use your patch below.
Thanks,
Ben
--
Ben Greear <greearb@candelatech•com>
Candela Technologies Inc http://www.candelatech.com
next prev parent reply other threads:[~2012-03-26 23:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-26 21:43 RCU lock bug in 3.0.21 (bisected to: 682cb56a, fix NULL dereferences in check_peer_redir) Ben Greear
2012-03-26 21:49 ` David Miller
2012-03-26 21:53 ` Ben Greear
2012-03-26 23:06 ` Ben Greear
2012-03-26 23:11 ` David Miller
2012-03-26 23:39 ` Eric Dumazet
2012-03-26 23:46 ` Ben Greear [this message]
2012-03-26 23:53 ` Ben Greear
2012-03-27 0:07 ` Eric Dumazet
2012-03-27 5:11 ` Paul E. McKenney
2012-03-27 5:30 ` Ben Greear
2012-03-27 16:47 ` Paul E. McKenney
2012-03-27 16:47 ` Ben Greear
2012-03-27 18:06 ` Eric Dumazet
2012-03-27 19:39 ` Eric Dumazet
2012-03-27 19:53 ` [PATCH] net: fix a potential rcu_read_lock() imbalance in rt6_fill_node() Eric Dumazet
2012-03-27 20:07 ` Ben Greear
2012-03-27 20:17 ` Ben Greear
2012-03-27 20:25 ` Greg KH
2012-03-27 22:22 ` David Miller
2012-03-28 0:54 ` John Fastabend
2012-03-28 1:27 ` David Miller
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