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Date: Thu, 2 Feb 2012 02:54:30 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com,
        dipankar@in.ibm.com, akpm@linux-foundation.org,
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        Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com,
        darren@dvhart.com, patches@linaro.org,
        "Paul E. McKenney" <paul.mckenney@linaro.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Len Brown <lenb@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
        Stephen Wilson <wilsons@start.ca>, linux-pm@vger.kernel.org,
        x86@kernel.org
Subject: Re: [PATCH RFC idle 1/3] x86: Avoid invoking RCU when CPU is idle
Message-ID: <20120202015428.GA8807@somewhere.redhat.com>
References: <20120202004253.GA10946@linux.vnet.ibm.com>
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On Wed, Feb 01, 2012 at 04:43:22PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@linaro.org>
> 
> The idle loop is a quiscent state for RCU, which means that RCU ignores
> CPUs that have told RCU that they are idle via rcu_idle_enter().  There
> are nevertheless quite a few places where idle CPUs use RCU, most commonly
> indirectly via tracing.  This patch fixes these problems for x86.
> 
> Many of these bugs have been in the kernel for quite some time, but
> Frederic's recent change now gives warnings.
> 
> This patch takes the straightforward approach of pushing the
> rcu_idle_enter()/rcu_idle_exit() pair further down into the core
> of the idle loop.

I guess this is about the trace_power_*() things, right?

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

Thanks.