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a71c8bc5df
CONFIG_DEBUG_HOTPLUG_CPU0 is for debugging 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. Please note that some applications or drivers, e.g. some versions of udevd, during boot time may put CPU0 online again in this CPU0 hotplug debug mode. In this debug mode, setup_local_APIC() may report a warning on max_loops<=0 when CPU0 is onlined back after boot time. This is because pending interrupt in IRR can not move to ISR. The warning is not CPU0 specfic and it can happen on other CPUs as well. It is harmless except the first CPU0 online takes a bit longer time. And so this debug mode is useful to expose this issue. I'll send a seperate patch to fix this generic warning issue. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Link: http://lkml.kernel.org/r/1352835171-3958-15-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
171 lines
4.0 KiB
C
171 lines
4.0 KiB
C
/*
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* Populate sysfs with topology information
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*
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* Written by: Matthew Dobson, IBM Corporation
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* Original Code: Paul Dorwin, IBM Corporation, Patrick Mochel, OSDL
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*
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* Copyright (C) 2002, IBM Corp.
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* Send feedback to <colpatch@us.ibm.com>
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*/
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#include <linux/nodemask.h>
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#include <linux/export.h>
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#include <linux/mmzone.h>
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/irq.h>
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#include <asm/cpu.h>
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static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
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#ifdef CONFIG_HOTPLUG_CPU
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#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
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static int cpu0_hotpluggable = 1;
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#else
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static int cpu0_hotpluggable;
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static int __init enable_cpu0_hotplug(char *str)
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{
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cpu0_hotpluggable = 1;
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return 1;
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}
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__setup("cpu0_hotplug", enable_cpu0_hotplug);
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#endif
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#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
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/*
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* This function offlines a CPU as early as possible and allows userspace to
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* boot up without the CPU. The CPU can be onlined back by user after boot.
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*
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* This is only called for debugging CPU offline/online feature.
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*/
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int __ref _debug_hotplug_cpu(int cpu, int action)
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{
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struct device *dev = get_cpu_device(cpu);
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int ret;
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if (!cpu_is_hotpluggable(cpu))
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return -EINVAL;
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cpu_hotplug_driver_lock();
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switch (action) {
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case 0:
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ret = cpu_down(cpu);
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if (!ret) {
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pr_info("CPU %u is now offline\n", cpu);
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kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
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} else
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pr_debug("Can't offline CPU%d.\n", cpu);
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break;
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case 1:
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ret = cpu_up(cpu);
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if (!ret)
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kobject_uevent(&dev->kobj, KOBJ_ONLINE);
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else
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pr_debug("Can't online CPU%d.\n", cpu);
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break;
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default:
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ret = -EINVAL;
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}
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cpu_hotplug_driver_unlock();
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return ret;
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}
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static int __init debug_hotplug_cpu(void)
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{
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_debug_hotplug_cpu(0, 0);
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return 0;
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}
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late_initcall_sync(debug_hotplug_cpu);
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#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
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int __ref arch_register_cpu(int num)
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{
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struct cpuinfo_x86 *c = &cpu_data(num);
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/*
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* Currently CPU0 is only hotpluggable on Intel platforms. Other
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* vendors can add hotplug support later.
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*/
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if (c->x86_vendor != X86_VENDOR_INTEL)
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cpu0_hotpluggable = 0;
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/*
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* Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
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* depends on BSP. PIC interrupts depend on BSP.
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*
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* If the BSP depencies are under control, one can tell kernel to
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* enable BSP hotplug. This basically adds a control file and
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* one can attempt to offline BSP.
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*/
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if (num == 0 && cpu0_hotpluggable) {
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unsigned int irq;
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/*
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* We won't take down the boot processor on i386 if some
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* interrupts only are able to be serviced by the BSP in PIC.
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*/
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for_each_active_irq(irq) {
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if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
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cpu0_hotpluggable = 0;
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break;
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}
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}
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}
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if (num || cpu0_hotpluggable)
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per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
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return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
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}
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EXPORT_SYMBOL(arch_register_cpu);
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void arch_unregister_cpu(int num)
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{
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unregister_cpu(&per_cpu(cpu_devices, num).cpu);
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}
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EXPORT_SYMBOL(arch_unregister_cpu);
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#else /* CONFIG_HOTPLUG_CPU */
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static int __init arch_register_cpu(int num)
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{
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return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
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}
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#endif /* CONFIG_HOTPLUG_CPU */
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static int __init topology_init(void)
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{
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int i;
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#ifdef CONFIG_NUMA
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for_each_online_node(i)
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register_one_node(i);
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#endif
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for_each_present_cpu(i)
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arch_register_cpu(i);
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return 0;
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}
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subsys_initcall(topology_init);
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