linux-kernel - Re: Question on lockdep and MAX_LOCK

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Date:	Wed, 06 Feb 2013 08:58:43 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: Question on lockdep and MAX_LOCK_DEPTH

On 02/06/2013 08:07 AM, Steven Rostedt wrote:
> On Wed, 2013-02-06 at 07:56 -0800, Ben Greear wrote:
>
>>> I'm 99% sure that the bug is in your modifications.
>>
>> I'm sorry, I tried to make that clear.
>
> You said it was an out of tree module, I didn't realize it had changes
> to the core Linux as well.
>
>
>> My tree is here, minus a few debugging patches related to this bug:
>>
>> http://dmz2.candelatech.com/git/gitweb.cgi?p=linux-3.7.dev.y/.git;a=summary
>
> Here's your bug:
>
> 3319         list_for_each_entry_rcu(ptype, &ptype_all, list) {
> 3320                 if (!ptype->dev || ptype->dev == skb->dev) {
> 3321                         if (pt_prev) {
> 3322                                 ret = deliver_skb(skb, pt_prev, orig_dev);
> 3323                                 if (ret == NET_RX_CONSUMED) {
> 3324                                         kfree_skb(skb); /* we made a copy in deliver_skb */
> 3325                                         goto out;
> 3326                                 }
> 3327                         }
>
> One of many. All those "goto out;"s skip the rcu_read_unlock().

Thank you so much!

I'll fix this and continue testing...

I can also post a patch to print the held locks when
the max-lock-depth overflows unless someone else prefers
to...

Thanks,
Ben


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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