From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757216Ab2EGSBX (ORCPT ); Mon, 7 May 2012 14:01:23 -0400 Received: from www.linutronix.de ([62.245.132.108]:41395 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753589Ab2EGR7v (ORCPT ); Mon, 7 May 2012 13:59:51 -0400 Message-Id: <20120507175651.980164748@linutronix.de> User-Agent: quilt/0.48-1 Date: Mon, 07 May 2012 17:59:47 -0000 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Deepthi Dharwar , Trinabh Gupta , Arun R Bharadwaj , Benjamin Herrenschmidt Subject: [patch 1/8] powerpc: Fix broken cpu_idle_wait() implementation References: <20120507175450.513667947@linutronix.de> Content-Disposition: inline; filename=power-fix-broken-cpu-idle-wait.patch X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org commit 771dae818 (powerpc/cpuidle: Add cpu_idle_wait() to allow switching of idle routines) implemented cpu_idle_wait() for powerpc. The changelog says: "The equivalent routine for x86 is in arch/x86/kernel/process.c but the powerpc implementation is different.": Unfortunately the changelog is completely useless as it does not tell _WHY_ it is different. Aside of being different the implementation is patently wrong. The rescheduling IPI is async. That means that there is no guarantee, that the other cores have executed the IPI when cpu_idle_wait() returns. But that's the whole purpose of this function: to guarantee that no CPU uses the old idle handler anymore. Use the smp_functional_call() based implementation, which fulfils the requirements. [ This code is going to replaced by a core version to remove all the pointless copies in arch/*, but this one should go to stable ] Signed-off-by: Thomas Gleixner Cc: Deepthi Dharwar Cc: Trinabh Gupta Cc: Arun R Bharadwaj Cc: Benjamin Herrenschmidt --- arch/powerpc/kernel/idle.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) Index: tip/arch/powerpc/kernel/idle.c =================================================================== --- tip.orig/arch/powerpc/kernel/idle.c +++ tip/arch/powerpc/kernel/idle.c @@ -113,6 +113,9 @@ void cpu_idle(void) } } +static void do_nothing(void *unused) +{ +} /* * cpu_idle_wait - Used to ensure that all the CPUs come out of the old @@ -123,16 +126,9 @@ void cpu_idle(void) */ void cpu_idle_wait(void) { - int cpu; smp_mb(); - - /* kick all the CPUs so that they exit out of old idle routine */ - get_online_cpus(); - for_each_online_cpu(cpu) { - if (cpu != smp_processor_id()) - smp_send_reschedule(cpu); - } - put_online_cpus(); + /* kick all the CPUs so that they exit out of pm_idle */ + smp_call_function(do_nothing, NULL, 1); } EXPORT_SYMBOL_GPL(cpu_idle_wait);