Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756716Ab3DMAtt (ORCPT ); Fri, 12 Apr 2013 20:49:49 -0400 Received: from wolverine01.qualcomm.com ([199.106.114.254]:58724 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755243Ab3DMAts (ORCPT ); Fri, 12 Apr 2013 20:49:48 -0400 X-IronPort-AV: E=Sophos;i="4.87,466,1363158000"; d="scan'208";a="38052609" Message-ID: <5168ABAB.4090402@codeaurora.org> Date: Fri, 12 Apr 2013 17:49:47 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: John Stultz , Thomas Gleixner CC: Marc Zyngier , Mark Rutland , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCHv2] ARM: arch_timer: Silence debug preempt warnings References: <1365195449-6755-1-git-send-email-sboyd@codeaurora.org> <211ac95efd49bd57933aec8c8e746648@localhost> In-Reply-To: <211ac95efd49bd57933aec8c8e746648@localhost> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2569 Lines: 73 On 04/06/13 03:41, Marc Zyngier wrote: > On Fri, 5 Apr 2013 13:57:29 -0700, Stephen Boyd > wrote: >> Hot-plugging with CONFIG_DEBUG_PREEMPT=y on a device with arm >> architected timers causes a slew of "using smp_processor_id() in >> preemptible" warnings: >> >> BUG: using smp_processor_id() in preemptible [00000000] code: sh/111 >> caller is arch_timer_cpu_notify+0x14/0xc8 >> >> This happens because sometimes the cpu notifier, >> arch_timer_cpu_notify(), is called in preemptible context and >> other times in non-preemptible context but we use this_cpu_ptr() >> to retrieve the clockevent in all cases. We're only going to >> actually use the pointer in non-preemptible context though, so >> push the this_cpu_ptr() access down into the cases to force the >> checks to occur only in non-preemptible contexts. >> >> Cc: Mark Rutland >> Cc: Marc Zyngier >> Signed-off-by: Stephen Boyd >> --- >> >> Changes since v1: >> * Pushed down this_cpu_ptr and added a comment >> >> drivers/clocksource/arm_arch_timer.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/clocksource/arm_arch_timer.c >> b/drivers/clocksource/arm_arch_timer.c >> index d7ad425..a65a710 100644 >> --- a/drivers/clocksource/arm_arch_timer.c >> +++ b/drivers/clocksource/arm_arch_timer.c >> @@ -248,14 +248,16 @@ static void __cpuinit arch_timer_stop(struct >> clock_event_device *clk) >> static int __cpuinit arch_timer_cpu_notify(struct notifier_block *self, >> unsigned long action, void *hcpu) >> { >> - struct clock_event_device *evt = this_cpu_ptr(arch_timer_evt); >> - >> + /* >> + * Grab cpu pointer in each case to avoid spurious >> + * preemptible warnings >> + */ >> switch (action & ~CPU_TASKS_FROZEN) { >> case CPU_STARTING: >> - arch_timer_setup(evt); >> + arch_timer_setup(this_cpu_ptr(arch_timer_evt)); >> break; >> case CPU_DYING: >> - arch_timer_stop(evt); >> + arch_timer_stop(this_cpu_ptr(arch_timer_evt)); >> break; >> } > Looks good to me. > > Acked-by: Marc Zyngier > Thanks Marc. Thomas/John, can you pick this up for 3.10? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- 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/