linux-kernel - Re: [PATCH] lockdep: Make lockstats counting per cpu

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Message-ID: <1269589714.12097.122.camel@laptop>
Date:	Fri, 26 Mar 2010 08:48:34 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] lockdep: Make lockstats counting per cpu

On Fri, 2010-03-26 at 07:52 +0100, Peter Zijlstra wrote:
> On Fri, 2010-03-26 at 03:22 +0100, Frederic Weisbecker wrote:
> > We can't use irqsafe per cpu counters for that as
> > these stats might be also written from NMI path, and irqsafe per
> > cpu counters are not NMI safe, but local_t operations are.
> > 
> lockdep shouldn't do NMI, nmi_enter() has an explicit lockdep_off().

Also, more importantly, you simply should never use locks in NMI context
to begin with ;-)

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