[ARM SMP] Add hotplug CPU infrastructure (a054a811) · Commits · e / devices / android_kernel_fairphone_FP5

arch/arm/Kconfig

+7 −0

Original line number	Original line	Diff line number	Diff line
	@@ -349,6 +349,13 @@ config NR_CPUS
	depends on SMP		depends on SMP
	default "4"		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		config PREEMPT
	bool "Preemptible Kernel (EXPERIMENTAL)"		bool "Preemptible Kernel (EXPERIMENTAL)"
	depends on EXPERIMENTAL		depends on EXPERIMENTAL

arch/arm/kernel/irq.c

+31 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1050,3 +1050,34 @@ static int __init noirqdebug_setup(char *str)
	}		}

	__setup("noirqdebug", noirqdebug_setup);		__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	Original line	Diff line number	Diff line
	@@ -26,6 +26,7 @@
	#include <linux/interrupt.h>		#include <linux/interrupt.h>
	#include <linux/kallsyms.h>		#include <linux/kallsyms.h>
	#include <linux/init.h>		#include <linux/init.h>
			#include <linux/cpu.h>

	#include <asm/system.h>		#include <asm/system.h>
	#include <asm/io.h>		#include <asm/io.h>
	@@ -105,6 +106,14 @@ void cpu_idle(void)
	/* endless idle loop with no priority at all */		/* endless idle loop with no priority at all */
	while (1) {		while (1) {
	void (*idle)(void) = pm_idle;		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)		if (!idle)
	idle = default_idle;		idle = default_idle;
	preempt_disable();		preempt_disable();

arch/arm/kernel/smp.c

+85 −0

Original line number	Original line	Diff line number	Diff line
	@@ -159,6 +159,91 @@ int __cpuinit __cpu_up(unsigned int cpu)
	return ret;		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		* This is the secondary CPU boot entry. We're using this CPUs
	* idle thread stack, but a set of temporary page tables.		* idle thread stack, but a set of temporary page tables.

include/asm-arm/irq.h

+1 −0

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

			extern void migrate_irqs(void);
	#endif		#endif