From: Jiang Liu <liuj97@gmail.com>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
H Peter Anvin <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Asit K Mallick <asit.k.mallick@intel.com>,
Tony Luck <tony.luck@intel.com>,
Arjan van de Ven <arjan.van.de.ven@intel.com>,
Suresh B Siddha <suresh.b.siddha@intel.com>,
Len Brown <len.brown@intel.com>,
Randy Dunlap <rdunlap@xenotime.net>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Chen Gong <gong.chen@linux.intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-pm <linux-pm@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v5 12/12] x86/topology.c: debug CPU0 hotplug
Date: Sun, 15 Jan 2012 23:24:14 +0800 [thread overview]
Message-ID: <4F12EF9E.6060104@gmail.com> (raw)
In-Reply-To: <1326301493-28760-13-git-send-email-fenghua.yu@intel.com>
On 01/12/2012 01:04 AM, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> CONFIG_DEBUG_HOTPLUG_CPU0 is for debuging the CPU0 hotplug feature. The switch
> offlines CPU0 as soon as possible and boots userspace up with CPU0 offlined.
> User can online CPU0 back after boot time. The default value of the switch is
> off.
>
> To debug CPU0 hotplug, you need to enable CPU0 offline/online feature by either
> turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during compilation or giving
> cpu0_hotplug kernel parameter at boot.
>
> It's safe and early place to take down CPU0 after all hotplug notifiers
> are installed and SMP is booted.
>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> arch/x86/Kconfig | 15 +++++++++++++++
> arch/x86/kernel/topology.c | 39 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 54 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c2cf195..36b6a2c 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1748,6 +1748,21 @@ config BOOTPARAM_HOTPLUG_CPU0
> You still can enable the CPU0 hotplug feature at boot by kernel
> parameter cpu0_hotplug.
>
> +config DEBUG_HOTPLUG_CPU0
> + def_bool n
> + prompt "Debug CPU0 hotplug"
> + depends on HOTPLUG_CPU && EXPERIMENTAL
> + ---help---
> + Enabling this option offlines CPU0 (if CPU0 can be offlined) as
> + soon as possible and boots up userspace with CPU0 offlined. User
> + can online CPU0 back after boot time.
> +
> + To debug CPU0 hotplug, you need to enable CPU0 offline/online
> + feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
> + compilation or giving cpu0_hotplug kernel parameter at boot.
> +
> + If unuser, say N.
> +
> config COMPAT_VDSO
> def_bool y
> prompt "Compat VDSO support"
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index 8cec15c..3f697dd 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -49,6 +49,45 @@ static int __init enable_cpu0_hotplug(char *str)
> __setup("cpu0_hotplug", enable_cpu0_hotplug);
> #endif
>
> +#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
> +/*
> + * This function offlines CPU0 as early as possible and allows userspace to
> + * boot up without CPU0. CPU0 can be onlined back by user after boot.
> + *
> + * This is only called for debugging CPU0 offline feature.
> + */
> +static void __init _debug_hotplug_cpu(int num)
> +{
> + int ret;
> + struct sys_device *dev = get_cpu_sysdev(num);
> +
> + /*
> + * Take hotpluggable online CPU0 down.
> + */
> + if (num || !per_cpu(cpu_devices, num).cpu.hotpluggable || !dev ||
> + !cpu_online(num)) {
> + pr_debug("CPU0 can't be offlined.\n");
> + return;
> + }
The usage of parameter num seems a little inconsistent.
Suggest either to remove the num parameter or to get rid of the assumption
that num is always zero.
> +
> + cpu_hotplug_driver_lock();
> +
> + ret = cpu_down(num);
> + if (!ret)
> + kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
> + else
> + pr_debug("Can't offline CPU%d.\n", num);
> +
> + cpu_hotplug_driver_unlock();
> +}
> +static int __init debug_hotplug_cpu(void)
> +{
> + _debug_hotplug_cpu(0);
> + return 0;
> +}
> +device_initcall_sync(debug_hotplug_cpu);
> +#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
> +
> int __ref arch_register_cpu(int num)
> {
> /*
prev parent reply other threads:[~2012-01-15 15:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 17:04 [PATCH v5 0/12] x86: Arbitrary CPU hot(un)plug support Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 01/12] Documentations/cpu-hotplug.tx, kernel-parameters.txt: Add x86 CPU0 online/offline feature Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 02/12] x86/Kconfig: Add config switch for CPU0 hotplug Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 03/12] x86/topology.c: Support functions for CPU0 online/offline Fenghua Yu
2012-01-16 17:35 ` Ben Hutchings
2012-01-24 22:31 ` Yu, Fenghua
2012-01-24 22:52 ` Ben Hutchings
2012-01-24 23:00 ` Yu, Fenghua
2012-01-11 17:04 ` [PATCH v5 04/12] x86/smpboot.c: Don't offline CPU0 if any irq can not be migrated out of it and remove CPU0 check in smp_callin() Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 05/12] x86/power/cpu.c: Don't hibernate/suspend if CPU0 is offline Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 06/12] x86/head_64.S: Define start_cpu0 Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 07/12] x86/head_32.S: " Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 08/12] x86/smpboot.c: Wake up CPU0 via NMI instead of INITs Fenghua Yu
2012-01-12 12:31 ` Brian Gerst
2012-01-11 17:04 ` [PATCH v5 09/12] x86/common.c: Init CPU0 data during CPU0 online Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 10/12] x86/mtrr/main.c: Ask the first online CPU to save mtrr Fenghua Yu
2012-01-12 12:33 ` Brian Gerst
2012-01-16 0:07 ` H. Peter Anvin
2012-01-25 17:58 ` Yu, Fenghua
2012-01-25 19:01 ` Yu, Fenghua
2012-01-11 17:04 ` [PATCH v5 11/12] x86/i387.c: Thread xstate is initialized only on CPU0 once Fenghua Yu
2012-01-11 17:04 ` [PATCH v5 12/12] x86/topology.c: debug CPU0 hotplug Fenghua Yu
2012-01-15 15:24 ` Jiang Liu [this message]
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