smp.c

linux 内核源代码

/*
 *  linux/arch/arm/kernel/smp.c
 *
 *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/cache.h>
#include <linux/profile.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/seq_file.h>
#include <linux/irq.h>

#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/cpu.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/ptrace.h>

/*
 * bitmask of present and online CPUs.
 * The present bitmask indicates that the CPU is physically present.
 * The online bitmask indicates that the CPU is up and running.
 */
cpumask_t cpu_possible_map;
EXPORT_SYMBOL(cpu_possible_map);
cpumask_t cpu_online_map;
EXPORT_SYMBOL(cpu_online_map);

/*
 * as from 2.5, kernels no longer have an init_tasks structure
 * so we need some other way of telling a new secondary core
 * where to place its SVC stack
 */
struct secondary_data secondary_data;

/*
 * structures for inter-processor calls
 * - A collection of single bit ipi messages.
 */
struct ipi_data {
	spinlock_t lock;
	unsigned long ipi_count;
	unsigned long bits;
};

static DEFINE_PER_CPU(struct ipi_data, ipi_data) = {
	.lock	= SPIN_LOCK_UNLOCKED,
};

enum ipi_msg_type {
	IPI_TIMER,
	IPI_RESCHEDULE,
	IPI_CALL_FUNC,
	IPI_CPU_STOP,
};

struct smp_call_struct {
	void (*func)(void *info);
	void *info;
	int wait;
	cpumask_t pending;
	cpumask_t unfinished;
};

static struct smp_call_struct * volatile smp_call_function_data;
static DEFINE_SPINLOCK(smp_call_function_lock);

int __cpuinit __cpu_up(unsigned int cpu)
{
	struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
	struct task_struct *idle = ci->idle;
	pgd_t *pgd;
	pmd_t *pmd;
	int ret;

	/*
	 * Spawn a new process manually, if not already done.
	 * Grab a pointer to its task struct so we can mess with it
	 */
	if (!idle) {
		idle = fork_idle(cpu);
		if (IS_ERR(idle)) {
			printk(KERN_ERR "CPU%u: fork() failed\n", cpu);
			return PTR_ERR(idle);
		}
		ci->idle = idle;
	}

	/*
	 * Allocate initial page tables to allow the new CPU to
	 * enable the MMU safely.  This essentially means a set
	 * of our "standard" page tables, with the addition of
	 * a 1:1 mapping for the physical address of the kernel.
	 */
	pgd = pgd_alloc(&init_mm);
	pmd = pmd_offset(pgd, PHYS_OFFSET);
	*pmd = __pmd((PHYS_OFFSET & PGDIR_MASK) |
		     PMD_TYPE_SECT | PMD_SECT_AP_WRITE);

	/*
	 * We need to tell the secondary core where to find
	 * its stack and the page tables.
	 */
	secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
	secondary_data.pgdir = virt_to_phys(pgd);
	wmb();

	/*
	 * Now bring the CPU into our world.
	 */
	ret = boot_secondary(cpu, idle);
	if (ret == 0) {
		unsigned long timeout;

		/*
		 * CPU was successfully started, wait for it
		 * to come online or time out.
		 */
		timeout = jiffies + HZ;
		while (time_before(jiffies, timeout)) {
			if (cpu_online(cpu))
				break;

			udelay(10);
			barrier();
		}

		if (!cpu_online(cpu))
			ret = -EIO;
	}

	secondary_data.stack = NULL;
	secondary_data.pgdir = 0;

	*pmd_offset(pgd, PHYS_OFFSET) = __pmd(0);
	pgd_free(pgd);

	if (ret) {
		printk(KERN_CRIT "CPU%u: processor failed to boot\n", cpu);

		/*
		 * FIXME: We need to clean up the new idle thread. --rmk
		 */
	}

	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();

	/*
	 * Stop the local timer for this CPU.
	 */
	local_timer_stop(cpu);

	/*
	 * 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" (task_stack_page(current) + 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.
 */
asmlinkage void __cpuinit secondary_start_kernel(void)
{
	struct mm_struct *mm = &init_mm;
	unsigned int cpu = smp_processor_id();

	printk("CPU%u: Booted secondary processor\n", cpu);

	/*
	 * All kernel threads share the same mm context; grab a
	 * reference and switch to it.
	 */
	atomic_inc(&mm->mm_users);
	atomic_inc(&mm->mm_count);
	current->active_mm = mm;
	cpu_set(cpu, mm->cpu_vm_mask);
	cpu_switch_mm(mm->pgd, mm);
	enter_lazy_tlb(mm, current);
	local_flush_tlb_all();

	cpu_init();
	preempt_disable();

	/*
	 * Give the platform a chance to do its own initialisation.
	 */
	platform_secondary_init(cpu);

	/*
	 * Enable local interrupts.
	 */
	local_irq_enable();
	local_fiq_enable();

	calibrate_delay();

	smp_store_cpu_info(cpu);

	/*
	 * OK, now it's safe to let the boot CPU continue
	 */
	cpu_set(cpu, cpu_online_map);

	/*
	 * Setup local timer for this CPU.
	 */
	local_timer_setup(cpu);

	/*
	 * OK, it's off to the idle thread for us
	 */
	cpu_idle();
}

/*
 * Called by both boot and secondaries to move global data into
 * per-processor storage.
 */
void __cpuinit smp_store_cpu_info(unsigned int cpuid)
{
	struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);

	cpu_info->loops_per_jiffy = loops_per_jiffy;
}

void __init smp_cpus_done(unsigned int max_cpus)
{
	int cpu;
	unsigned long bogosum = 0;

	for_each_online_cpu(cpu)
		bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;

	printk(KERN_INFO "SMP: Total of %d processors activated "
	       "(%lu.%02lu BogoMIPS).\n",
	       num_online_cpus(),
	       bogosum / (500000/HZ),
	       (bogosum / (5000/HZ)) % 100);
}

void __init smp_prepare_boot_cpu(void)
{
	unsigned int cpu = smp_processor_id();

	per_cpu(cpu_data, cpu).idle = current;
}

static void send_ipi_message(cpumask_t callmap, enum ipi_msg_type msg)
{
	unsigned long flags;
	unsigned int cpu;

	local_irq_save(flags);

	for_each_cpu_mask(cpu, callmap) {
		struct ipi_data *ipi = &per_cpu(ipi_data, cpu);

		spin_lock(&ipi->lock);
		ipi->bits |= 1 << msg;
		spin_unlock(&ipi->lock);
	}

	/*
	 * Call the platform specific cross-CPU call function.
	 */
	smp_cross_call(callmap);

	local_irq_restore(flags);
}

/*
 * You must not call this function with disabled interrupts, from a
 * hardware interrupt handler, nor from a bottom half handler.
 */
static int smp_call_function_on_cpu(void (*func)(void *info), void *info,
				    int retry, int wait, cpumask_t callmap)
{
	struct smp_call_struct data;
	unsigned long timeout;
	int ret = 0;

	data.func = func;
	data.info = info;