From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756016Ab2BCLCi (ORCPT ); Fri, 3 Feb 2012 06:02:38 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:52583 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755406Ab2BCLCg (ORCPT ); Fri, 3 Feb 2012 06:02:36 -0500 Message-ID: <4F2BBEB3.7080802@linux.vnet.ibm.com> Date: Fri, 03 Feb 2012 16:32:11 +0530 From: Deepthi Dharwar User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.23) Gecko/20110922 Thunderbird/3.1.15 MIME-Version: 1.0 To: "Paul E. McKenney" CC: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" , Kevin Hilman , Len Brown , Trinabh Gupta , Arjan van de Ven Subject: Re: [PATCH RFC tip/core/rcu 3/3] cpuidle: Inform RCU of read-side critical sections References: <20120203011208.GA2004@linux.vnet.ibm.com> <1328231568-2971-1-git-send-email-paulmck@linux.vnet.ibm.com> <1328231568-2971-3-git-send-email-paulmck@linux.vnet.ibm.com> In-Reply-To: <1328231568-2971-3-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12020300-1396-0000-0000-0000009FB0F4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/03/2012 06:42 AM, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > The cpuidle_idle_call() function is invoked in the inner idle loop, > after the call to rcu_idle_enter() and before the call to rcu_idle_exit(). > This means that RCU is ignoring the CPU at this point. Unfortunately, > cpuidle_idle_call() nevertheless contains tracepoints (important ones > used by powertop) that expect RCU to be paying attention. The consequences > of using RCU read-side critical sections on CPUs that RCU is ignoring > can be severe, including random corruption of random memory. > > Therefore, this commit uses the new RCU_NONIDLE() macro to let RCU > do its job with respect to the tracepoints. > > Suggested-by: Nicolas Pitre > Signed-off-by: Paul E. McKenney > Signed-off-by: Paul E. McKenney > Cc: Kevin Hilman > Cc: Len Brown > Cc: Trinabh Gupta > Cc: Arjan van de Ven > Cc: Deepthi Dharwar > --- > drivers/cpuidle/cpuidle.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 59f4261..cd8a553 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -94,13 +94,17 @@ int cpuidle_idle_call(void) > > target_state = &drv->states[next_state]; > > - trace_power_start(POWER_CSTATE, next_state, dev->cpu); > - trace_cpu_idle(next_state, dev->cpu); > + RCU_NONIDLE( > + trace_power_start(POWER_CSTATE, next_state, dev->cpu); > + trace_cpu_idle(next_state, dev->cpu) > + ); > > entered_state = target_state->enter(dev, drv, next_state); > > - trace_power_end(dev->cpu); > - trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu); > + RCU_NONIDLE( > + trace_power_end(dev->cpu); > + trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu); > + ); > > if (entered_state >= 0) { > /* Update cpuidle counters */ Cleaner design esp by moving away from architecture specific tweaking is much appreciated :) Acked-by: Deepthi Dharwar