linux-kernel - Re: [PATCH RFC idle] Make arm, sh, and x86 stop using RCU when idle

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Date:	Wed, 1 Feb 2012 16:48:29 -0800
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org
Subject: Re: [PATCH RFC idle] Make arm, sh, and x86 stop using RCU when idle

On Wed, Feb 01, 2012 at 04:42:53PM -0800, Paul E. McKenney wrote:
> RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle
> located a few problems in arm, sh, and x86.  This patch series contains
> alleged fixes for these problems.  And they are real problems -- if RCU
> believes that the CPU is idle, it is ignoring it.  Which means that the
> idle CPU can say "rcu_read_lock()" all it like, but there will be no
> useful effect.

Having to put these calls down in every idle driver seems like such an
ugly layering violation.  Not that I have a better alternative to
suggest...

- Josh Triplett
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