netdev - Re: [PATCH] fix CONFIG_TCP_MD5SIG + CONFIG

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Date:	Tue, 15 Sep 2009 23:49:42 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nite@...alert.sk
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()

From: Robert Varga <nite@...alert.sk>
Date: Wed, 16 Sep 2009 01:01:26 +0200

> Hi,
> 
> I have recently came across a preemption imbalance detected by:
> 
> <4>huh, entered ffffffff80644630 with preempt_count 00000102, exited with 00000101?
> <0>------------[ cut here ]------------
> <2>kernel BUG at /usr/src/linux/kernel/timer.c:664!
> <0>invalid opcode: 0000 [1] PREEMPT SMP
> 
> with ffffffff80644630 being inet_twdr_hangman().
> 
> This appeared after I enabled CONFIG_TCP_MD5SIG and played with it a
> bit, so I looked at what might have caused it.
> 
> One thing that struck me as strange is tcp_twsk_destructor(), as it
> calls tcp_put_md5sig_pool() -- which entails a put_cpu(), causing the
> detected imbalance. Found on 2.6.23.9, but 2.6.31 is affected as well,
> as far as I can tell.
> 
> Signed-off-by: Robert Varga <nite@...alert.sk>

Looks good, applied and queued up for stable.

Thanks!
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