linux-kernel - Re: [LOCKDEP BUG][2.6.36-rc1] xt_info

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Message-Id: <20100816.124400.42792595.davem@davemloft.net>
Date:	Mon, 16 Aug 2010 12:44:00 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	rostedt@...dmis.org
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kaber@...sh.net, mingo@...e.hu,
	peterz@...radead.org
Subject: Re: [LOCKDEP BUG][2.6.36-rc1] xt_info_wrlock?

From: Steven Rostedt <rostedt@...dmis.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.

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