diff options
| -rw-r--r-- | arch/x86/Kconfig | 15 | ||||
| -rw-r--r-- | arch/x86/include/asm/cpu.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/topology.c | 51 | ||||
| -rw-r--r-- | arch/x86/power/cpu.c | 38 |
4 files changed, 107 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 036e89ab470c..b6cfa5f62529 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1727,6 +1727,21 @@ 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 unsure, say N. + config COMPAT_VDSO def_bool y prompt "Compat VDSO support" diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index a1195726e8c2..5f9a1243190e 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -29,6 +29,9 @@ struct x86_cpu { extern int arch_register_cpu(int num); extern void arch_unregister_cpu(int); extern void __cpuinit start_cpu0(void); +#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 +extern int _debug_hotplug_cpu(int cpu, int action); +#endif #endif DECLARE_PER_CPU(int, cpu_state); diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index 0e7b4a7a7fb8..6e60b5fe2244 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -50,6 +50,57 @@ static int __init enable_cpu0_hotplug(char *str) __setup("cpu0_hotplug", enable_cpu0_hotplug); #endif +#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 +/* + * This function offlines a CPU as early as possible and allows userspace to + * boot up without the CPU. The CPU can be onlined back by user after boot. + * + * This is only called for debugging CPU offline/online feature. + */ +int __ref _debug_hotplug_cpu(int cpu, int action) +{ + struct device *dev = get_cpu_device(cpu); + int ret; + + if (!cpu_is_hotpluggable(cpu)) + return -EINVAL; + + cpu_hotplug_driver_lock(); + + switch (action) { + case 0: + ret = cpu_down(cpu); + if (!ret) { + pr_info("CPU %u is now offline\n", cpu); + kobject_uevent(&dev->kobj, KOBJ_OFFLINE); + } else + pr_debug("Can't offline CPU%d.\n", cpu); + break; + case 1: + ret = cpu_up(cpu); + if (!ret) + kobject_uevent(&dev->kobj, KOBJ_ONLINE); + else + pr_debug("Can't online CPU%d.\n", cpu); + break; + default: + ret = -EINVAL; + } + + cpu_hotplug_driver_unlock(); + + return ret; +} + +static int __init debug_hotplug_cpu(void) +{ + _debug_hotplug_cpu(0, 0); + return 0; +} + +late_initcall_sync(debug_hotplug_cpu); +#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */ + int __ref arch_register_cpu(int num) { struct cpuinfo_x86 *c = &cpu_data(num); diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index adde77588e25..120cee1c3f8d 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -21,6 +21,7 @@ #include <asm/suspend.h> #include <asm/debugreg.h> #include <asm/fpu-internal.h> /* pcntxt_mask */ +#include <asm/cpu.h> #ifdef CONFIG_X86_32 static struct saved_context saved_context; @@ -263,6 +264,43 @@ static int bsp_pm_callback(struct notifier_block *nb, unsigned long action, case PM_HIBERNATION_PREPARE: ret = bsp_check(); break; +#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 + case PM_RESTORE_PREPARE: + /* + * When system resumes from hibernation, online CPU0 because + * 1. it's required for resume and + * 2. the CPU was online before hibernation + */ + if (!cpu_online(0)) + _debug_hotplug_cpu(0, 1); + break; + case PM_POST_RESTORE: + /* + * When a resume really happens, this code won't be called. + * + * This code is called only when user space hibernation software + * prepares for snapshot device during boot time. So we just + * call _debug_hotplug_cpu() to restore to CPU0's state prior to + * preparing the snapshot device. + * + * This works for normal boot case in our CPU0 hotplug debug + * mode, i.e. CPU0 is offline and user mode hibernation + * software initializes during boot time. + * + * If CPU0 is online and user application accesses snapshot + * device after boot time, this will offline CPU0 and user may + * see different CPU0 state before and after accessing + * the snapshot device. But hopefully this is not a case when + * user debugging CPU0 hotplug. Even if users hit this case, + * they can easily online CPU0 back. + * + * To simplify this debug code, we only consider normal boot + * case. Otherwise we need to remember CPU0's state and restore + * to that state and resolve racy conditions etc. + */ + _debug_hotplug_cpu(0, 0); + break; +#endif default: break; } |