diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/Kconfig | 7 | ||||
| -rw-r--r-- | arch/arm/kernel/irq.c | 31 | ||||
| -rw-r--r-- | arch/arm/kernel/process.c | 9 | ||||
| -rw-r--r-- | arch/arm/kernel/smp.c | 85 |
4 files changed, 132 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index dc6d8342e5e6..6b12d71978de 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -349,6 +349,13 @@ config NR_CPUS depends on SMP default "4" +config HOTPLUG_CPU + bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" + depends on SMP && HOTPLUG && EXPERIMENTAL + help + Say Y here to experiment with turning CPUs off and on. CPUs + can be controlled through /sys/devices/system/cpu. + config PREEMPT bool "Preemptible Kernel (EXPERIMENTAL)" depends on EXPERIMENTAL diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c index 3284118f356b..9def4404e1f2 100644 --- a/arch/arm/kernel/irq.c +++ b/arch/arm/kernel/irq.c @@ -1050,3 +1050,34 @@ static int __init noirqdebug_setup(char *str) } __setup("noirqdebug", noirqdebug_setup); + +#ifdef CONFIG_HOTPLUG_CPU +/* + * The CPU has been marked offline. Migrate IRQs off this CPU. If + * the affinity settings do not allow other CPUs, force them onto any + * available CPU. + */ +void migrate_irqs(void) +{ + unsigned int i, cpu = smp_processor_id(); + + for (i = 0; i < NR_IRQS; i++) { + struct irqdesc *desc = irq_desc + i; + + if (desc->cpu == cpu) { + unsigned int newcpu = any_online_cpu(desc->affinity); + + if (newcpu == NR_CPUS) { + if (printk_ratelimit()) + printk(KERN_INFO "IRQ%u no longer affine to CPU%u\n", + i, cpu); + + cpus_setall(desc->affinity); + newcpu = any_online_cpu(desc->affinity); + } + + route_irq(desc, i, newcpu); + } + } +} +#endif /* CONFIG_HOTPLUG_CPU */ diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 409db6d5ec99..ba298277becd 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -26,6 +26,7 @@ #include <linux/interrupt.h> #include <linux/kallsyms.h> #include <linux/init.h> +#include <linux/cpu.h> #include <asm/system.h> #include <asm/io.h> @@ -105,6 +106,14 @@ void cpu_idle(void) /* endless idle loop with no priority at all */ while (1) { void (*idle)(void) = pm_idle; + +#ifdef CONFIG_HOTPLUG_CPU + if (cpu_is_offline(smp_processor_id())) { + leds_event(led_idle_start); + cpu_die(); + } +#endif + if (!idle) idle = default_idle; preempt_disable(); diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index b40915dcd533..edb5a406922f 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -159,6 +159,91 @@ int __cpuinit __cpu_up(unsigned int cpu) return ret; } +#ifdef CONFIG_HOTPLUG_CPU +/* + * __cpu_disable runs on the processor to be shutdown. + */ +int __cpuexit __cpu_disable(void) +{ + unsigned int cpu = smp_processor_id(); + struct task_struct *p; + int ret; + + ret = mach_cpu_disable(cpu); + if (ret) + return ret; + + /* + * Take this CPU offline. Once we clear this, we can't return, + * and we must not schedule until we're ready to give up the cpu. + */ + cpu_clear(cpu, cpu_online_map); + + /* + * OK - migrate IRQs away from this CPU + */ + migrate_irqs(); + + /* + * Flush user cache and TLB mappings, and then remove this CPU + * from the vm mask set of all processes. + */ + flush_cache_all(); + local_flush_tlb_all(); + + read_lock(&tasklist_lock); + for_each_process(p) { + if (p->mm) + cpu_clear(cpu, p->mm->cpu_vm_mask); + } + read_unlock(&tasklist_lock); + + return 0; +} + +/* + * called on the thread which is asking for a CPU to be shutdown - + * waits until shutdown has completed, or it is timed out. + */ +void __cpuexit __cpu_die(unsigned int cpu) +{ + if (!platform_cpu_kill(cpu)) + printk("CPU%u: unable to kill\n", cpu); +} + +/* + * Called from the idle thread for the CPU which has been shutdown. + * + * Note that we disable IRQs here, but do not re-enable them + * before returning to the caller. This is also the behaviour + * of the other hotplug-cpu capable cores, so presumably coming + * out of idle fixes this. + */ +void __cpuexit cpu_die(void) +{ + unsigned int cpu = smp_processor_id(); + + local_irq_disable(); + idle_task_exit(); + + /* + * actual CPU shutdown procedure is at least platform (if not + * CPU) specific + */ + platform_cpu_die(cpu); + + /* + * Do not return to the idle loop - jump back to the secondary + * cpu initialisation. There's some initialisation which needs + * to be repeated to undo the effects of taking the CPU offline. + */ + __asm__("mov sp, %0\n" + " b secondary_start_kernel" + : + : "r" ((void *)current->thread_info + THREAD_SIZE - 8)); +} +#endif /* CONFIG_HOTPLUG_CPU */ + /* * This is the secondary CPU boot entry. We're using this CPUs * idle thread stack, but a set of temporary page tables. |