linux-kernel - Re: Kernel oops when clearing bgp neighbor info with TCP MD5SUM enabled

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Date:	Mon, 19 Oct 2009 08:32:07 -0700
From:	Anirban Sinha <ani@...rban.org>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	netdev@...r.kernel.org, Anirban Sinha <asinha@...gmasystems.com>
Subject: Re: Kernel oops when clearing bgp neighbor info with TCP MD5SUM enabled



Once upon a time, like on 09-10-19 5:13 AM, Oleg Nesterov wrote:
> Hi Anirban,
> 
> On 10/18, Anirban Sinha wrote:
>>
>> I have a question for you. The queue_work() routine which is called from
>> schedule_work() does a put_cpu() which in turn does a enable_preempt(). Is
>> this an attempt to trigger the scheduler?
> 
> No. please note that queue_work() does get_cpu() + put_cpu() to protect
> against cpu_down() in between.

grrr! Ah yes, my eyes failed me (or it saw what I wanted it to see :)). You do have a get_cpu() and put_cpu() together in the same code path. I guess I will have to keep looking at inet_twdr_hangman(). 

>> Is is
>> it illegal to schedule a work function from within a timer callback?
> 
> Yes sure.

hmm. may be in that case, that function needs to be re-written. 

> I'd suppose that this unbalance comes from inet_twdr_hangman() pathes.
> 
> Could you verify this?

I'll keep looking. Thanks for the help Oleg. 

Ani

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