[ARM SMP] Add hotplug CPU infrastructure (a054a811) · Commits · EulixOS / Software / Kernel

arch/arm/Kconfig

+7 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/arm/kernel/irq.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -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 */

arch/arm/kernel/process.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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();

arch/arm/kernel/smp.c

+85 −0

Original line number	Diff line number	Diff line
		@@ -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.

include/asm-arm/irq.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -47,5 +47,6 @@ struct irqaction;
		struct pt_regs;
		int handle_IRQ_event(unsigned int, struct pt_regs , struct irqaction );

		extern void migrate_irqs(void);
		#endif