Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755655Ab3DAB4x (ORCPT ); Sun, 31 Mar 2013 21:56:53 -0400 Received: from mail-vc0-f177.google.com ([209.85.220.177]:61446 "EHLO mail-vc0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752907Ab3DAB4v convert rfc822-to-8bit (ORCPT ); Sun, 31 Mar 2013 21:56:51 -0400 MIME-Version: 1.0 In-Reply-To: <5158C9B8.3070208@linaro.org> References: <1364549049-29278-1-git-send-email-ning.n.jiang@gmail.com> <5158C9B8.3070208@linaro.org> Date: Mon, 1 Apr 2013 09:56:50 +0800 Message-ID: Subject: Re: [PATCH] ARM: timer: Shutdown clock event device when stopping local timer From: Ning Jiang To: Daniel Lezcano Cc: linux@arm.linux.org.uk, kgene.kim@samsung.com, davidb@codeaurora.org, dwalker@fifo99.com, bryanh@codeaurora.org, john.stultz@linaro.org, tglx@linutronix.de, linus.walleij@linaro.org, shawn.guo@linaro.org, rob.herring@calxeda.com, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-msm@vger.kernel.org Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2482 Lines: 59 2013/4/1 Daniel Lezcano : > On 03/29/2013 10:24 AM, ning.n.jiang@gmail.com wrote: >> From: Ning Jiang >> >> Currently there are two problems when we try to stop local timer. >> First, it calls set_mode function directly so mode state is not >> updated for the clock event device. Second, it makes the device >> unused instead of shutdown. >> >> A subtle error will happen because of it. When a cpu is plugged out >> it will stop the local timer. It will call tick_nohz_idle_enter() >> in idle thread afterwards. It will cancel the sched timer and try >> to reprogram the next event. This is wrong since the local timer >> is supposed to be stopped. >> >> The right way to stop the local timer is to shutdown it by calling >> clockevents_set_mode(). Thus when we try to reprogram the clock >> event device, it will return directly without doing anything since >> the clock mode is CLOCK_EVT_MODE_SHUTDOWN. >> >> Signed-off-by: Ning Jiang >> --- >> arch/arm/kernel/smp_twd.c | 2 +- >> arch/arm/mach-exynos/mct.c | 2 +- >> arch/arm/mach-msm/timer.c | 2 +- >> drivers/clocksource/arm_arch_timer.c | 2 +- >> drivers/clocksource/time-armada-370-xp.c | 2 +- >> 5 files changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c >> index 3f25650..c1d4ab4 100644 >> --- a/arch/arm/kernel/smp_twd.c >> +++ b/arch/arm/kernel/smp_twd.c >> @@ -92,7 +92,7 @@ static int twd_timer_ack(void) >> >> static void twd_timer_stop(struct clock_event_device *clk) >> { >> - twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk); >> + clockevents_set_mode(clk, CLOCK_EVT_MODE_SHUTDOWN); >> disable_percpu_irq(clk->irq); > > Wouldn't be clockevents_shutdown more adequate here ? The next event > will be also set. You're right. clockevents_shutdown seems more appropriate here. I'll submit a revised patch for it. > -- > Linaro.org ? Open source software for ARM SoCs > > Follow Linaro: Facebook | > Twitter | > Blog > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/