Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753575Ab2JPFgn (ORCPT ); Tue, 16 Oct 2012 01:36:43 -0400 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:58796 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752079Ab2JPFgm (ORCPT ); Tue, 16 Oct 2012 01:36:42 -0400 Message-ID: <507CF216.3010507@linux.vnet.ibm.com> Date: Tue, 16 Oct 2012 11:05:18 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: Fenghua Yu , Ingo Molnar , Thomas Gleixner , H Peter Anvin , Linus Torvalds , Andrew Morton , Asit K Mallick , Tony Luck , Arjan Dan De Ven , Suresh B Siddha , Len Brown , Randy Dunlap , Chen Gong , linux-kernel , linux-pm , x86 Subject: Re: [PATCH v9 05/12] x86, hotplug, suspend: Online CPU0 for suspend or hibernate References: <1350058189-6769-1-git-send-email-fenghua.yu@intel.com> <1350058189-6769-6-git-send-email-fenghua.yu@intel.com> <10020874.9eDCB3ZAkx@vostro.rjw.lan> In-Reply-To: <10020874.9eDCB3ZAkx@vostro.rjw.lan> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit x-cbid: 12101605-4790-0000-0000-00000516E6ED Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2786 Lines: 91 On 10/16/2012 02:20 AM, Rafael J. Wysocki wrote: > On Friday 12 of October 2012 09:09:42 Fenghua Yu wrote: >> From: Fenghua Yu >> >> Because x86 BIOS requires CPU0 to resume from sleep, suspend or hibernate can't >> be executed if CPU0 is detected offline. To make suspend or hibernate and >> further resume succeed, CPU0 must be online. >> >> Signed-off-by: Fenghua Yu >> --- >> arch/x86/power/cpu.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ >> 1 files changed, 44 insertions(+), 0 deletions(-) >> >> diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c >> index 218cdb1..adde775 100644 >> --- a/arch/x86/power/cpu.c >> +++ b/arch/x86/power/cpu.c >> @@ -237,3 +237,47 @@ void restore_processor_state(void) >> #ifdef CONFIG_X86_32 >> EXPORT_SYMBOL(restore_processor_state); >> #endif >> + >> +/* >> + * When bsp_check() is called in hibernate and suspend, cpu hotplug >> + * is disabled already. So it's unnessary to handle race condition between >> + * cpumask query and cpu hotplug. >> + */ >> +static int bsp_check(void) >> +{ >> + if (cpumask_first(cpu_online_mask) != 0) { >> + pr_warn("CPU0 is offline.\n"); >> + return -ENODEV; >> + } >> + >> + return 0; >> +} >> + >> +static int bsp_pm_callback(struct notifier_block *nb, unsigned long action, >> + void *ptr) >> +{ >> + int ret = 0; >> + >> + switch (action) { >> + case PM_SUSPEND_PREPARE: >> + case PM_HIBERNATION_PREPARE: >> + ret = bsp_check(); >> + break; >> + default: >> + break; >> + } >> + return notifier_from_errno(ret); >> +} >> + > > I wonder if there's anything preventing CPU0 from becoming offline after you've > done this check and before user space is frozen? > Hi Rafael, bsp_pm_callback runs as a low priority notifier callback, specifically with lower priority than the cpu_hotplug_pm_callback (as mentioned in the comment below). And cpu_hotplug_pm_callback disables regular CPU hotplug (till the suspend/resume sequence is complete).. So there is no chance for CPU0 to become offline after that. Or, are you thinking of some other scenario where CPU0 can go offline? Regards, Srivatsa S. Bhat > > >> +static int __init bsp_pm_check_init(void) >> +{ >> + /* >> + * Set this bsp_pm_callback as lower priority than >> + * cpu_hotplug_pm_callback. So cpu_hotplug_pm_callback will be called >> + * earlier to disable cpu hotplug before bsp online check. >> + */ >> + pm_notifier(bsp_pm_callback, -INT_MAX); >> + return 0; >> +} >> + >> +core_initcall(bsp_pm_check_init); >> -- 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/