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Date: Mon, 16 Aug 2010 12:44:00 -0700 (PDT)
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To: rostedt@goodmis.org
Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, kaber@trash.net, mingo@elte.hu,
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Subject: Re: [LOCKDEP BUG][2.6.36-rc1] xt_info_wrlock?
From: David Miller <davem@davemloft.net>
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From: Steven Rostedt <rostedt@goodmis.org>
Date: Mon, 16 Aug 2010 13:55:01 -0400

> Please tell me what prevents an interrupt going off after we grab the
> xt_info_wrlock(cpu) in get_counters().

He's only accessing the per-cpu counter locks of other cpus.

The per-cpu lock is only locally accessed by a cpu in software
interrupt context.

That is why his transformation is legal.

Lockdep simply hasn't been informed of this invariant and has
to assume the worst.