smpboot.c

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/*
 * Copyright 2010 Tilera Corporation. 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
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/bootmem.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>

/* State of each CPU. */
static DEFINE_PER_CPU(int, cpu_state) = { 0 };

/* The messaging code jumps to this pointer during boot-up */
unsigned long start_cpu_function_addr;

/* Called very early during startup to mark boot cpu as online */
void __init smp_prepare_boot_cpu(void)
{
    int cpu = smp_processor_id();
    set_cpu_online(cpu, 1);
    set_cpu_present(cpu, 1);
    __get_cpu_var(cpu_state) = CPU_ONLINE;

    init_messaging();
}

static void start_secondary(void);

/*
 * Called at the top of init() to launch all the other CPUs.
 * They run free to complete their initialization and then wait
 * until they get an IPI from the boot cpu to come online.
 */
void __init smp_prepare_cpus(unsigned int max_cpus)
{
    long rc;
    int cpu, cpu_count;
    int boot_cpu = smp_processor_id();

    current_thread_info()->cpu = boot_cpu;

    /*
     * Pin this task to the boot CPU while we bring up the others,
     * just to make sure we don't uselessly migrate as they come up.
     */
    rc = sched_setaffinity(current->pid, cpumask_of(boot_cpu));
    if (rc != 0)
        pr_err("Couldn't set init affinity to boot cpu (%ld)\n", rc);

    /* Print information about disabled and dataplane cpus. */
    print_disabled_cpus();

    /*
     * Tell the messaging subsystem how to respond to the
     * startup message.  We use a level of indirection to avoid
     * confusing the linker with the fact that the messaging
     * subsystem is calling __init code.
     */
    start_cpu_function_addr = (unsigned long) &online_secondary;

    /* Set up thread context for all new processors. */
    cpu_count = 1;
    for (cpu = 0; cpu < NR_CPUS; ++cpu) {
        struct task_struct *idle;

        if (cpu == boot_cpu)
            continue;

        if (!cpu_possible(cpu)) {
            /*
             * Make this processor do nothing on boot.
             * Note that we don't give the boot_pc function
             * a stack, so it has to be assembly code.
             */
            per_cpu(boot_sp, cpu) = 0;
            per_cpu(boot_pc, cpu) = (unsigned long) smp_nap;
            continue;
        }

        /* Create a new idle thread to run start_secondary() */
        idle = fork_idle(cpu);
        if (IS_ERR(idle))
            panic("failed fork for CPU %d", cpu);
        idle->thread.pc = (unsigned long) start_secondary;

        /* Make this thread the boot thread for this processor */
        per_cpu(boot_sp, cpu) = task_ksp0(idle);
        per_cpu(boot_pc, cpu) = idle->thread.pc;

        ++cpu_count;
    }
    BUG_ON(cpu_count > (max_cpus ? max_cpus : 1));

    /* Fire up the other tiles, if any */
    init_cpu_present(cpu_possible_mask);
    if (cpumask_weight(cpu_present_mask) > 1) {
        mb();  /* make sure all data is visible to new processors */
        hv_start_all_tiles();
    }
}

static __initdata struct cpumask init_affinity;

static __init int reset_init_affinity(void)
{
    long rc = sched_setaffinity(current->pid, &init_affinity);
    if (rc != 0)
        pr_warning("couldn't reset init affinity (%ld)\n",
               rc);
    return 0;
}
late_initcall(reset_init_affinity);

static struct cpumask cpu_started __cpuinitdata;

/*
 * Activate a secondary processor.  Very minimal; don't add anything
 * to this path without knowing what you're doing, since SMP booting
 * is pretty fragile.
 */
static void __cpuinit start_secondary(void)
{
    int cpuid = smp_processor_id();

    /* Set our thread pointer appropriately. */
    set_my_cpu_offset(__per_cpu_offset[cpuid]);

    preempt_disable();

    /*
     * In large machines even this will slow us down, since we
     * will be contending for for the printk spinlock.
     */
    /* printk(KERN_DEBUG "Initializing CPU#%d\n", cpuid); */

    /* Initialize the current asid for our first page table. */
    __get_cpu_var(current_asid) = min_asid;

    /* Set up this thread as another owner of the init_mm */
    atomic_inc(&init_mm.mm_count);
    current->active_mm = &init_mm;
    if (current->mm)
        BUG();
    enter_lazy_tlb(&init_mm, current);

    /* Allow hypervisor messages to be received */
    init_messaging();
    local_irq_enable();

    /* Indicate that we're ready to come up. */
    /* Must not do this before we're ready to receive messages */
    if (cpumask_test_and_set_cpu(cpuid, &cpu_started)) {
        pr_warning("CPU#%d already started!\n", cpuid);
        for (;;)
            local_irq_enable();
    }

    smp_nap();
}

/*
 * Bring a secondary processor online.
 */
void __cpuinit online_secondary(void)
{
    /*
     * low-memory mappings have been cleared, flush them from
     * the local TLBs too.
     */
    local_flush_tlb();

    BUG_ON(in_interrupt());

    /* This must be done before setting cpu_online_mask */
    wmb();

    notify_cpu_starting(smp_processor_id());

    set_cpu_online(smp_processor_id(), 1);
    __get_cpu_var(cpu_state) = CPU_ONLINE;

    /* Set up tile-specific state for this cpu. */
    setup_cpu(0);

    /* Set up tile-timer clock-event device on this cpu */
    setup_tile_timer();

    preempt_enable();

    cpu_idle();
}

int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
    /* Wait 5s total for all CPUs for them to come online */
    static int timeout;
    for (; !cpumask_test_cpu(cpu, &cpu_started); timeout++) {
        if (timeout >= 50000) {
            pr_info("skipping unresponsive cpu%d\n", cpu);
            local_irq_enable();
            return -EIO;
        }
        udelay(100);
    }

    local_irq_enable();
    per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

    /* Unleash the CPU! */
    send_IPI_single(cpu, MSG_TAG_START_CPU);
    while (!cpumask_test_cpu(cpu, cpu_online_mask))
        cpu_relax();
    return 0;
}

static void panic_start_cpu(void)
{
    panic("Received a MSG_START_CPU IPI after boot finished.");
}

void __init smp_cpus_done(unsigned int max_cpus)
{
    int cpu, next, rc;

    /* Reset the response to a (now illegal) MSG_START_CPU IPI. */
    start_cpu_function_addr = (unsigned long) &panic_start_cpu;

    cpumask_copy(&init_affinity, cpu_online_mask);

    /*
     * Pin ourselves to a single cpu in the initial affinity set
     * so that kernel mappings for the rootfs are not in the dataplane,
     * if set, and to avoid unnecessary migrating during bringup.
     * Use the last cpu just in case the whole chip has been
     * isolated from the scheduler, to keep init away from likely
     * more useful user code.  This also ensures that work scheduled
     * via schedule_delayed_work() in the init routines will land
     * on this cpu.
     */
    for (cpu = cpumask_first(&init_affinity);
         (next = cpumask_next(cpu, &init_affinity)) < nr_cpu_ids;
         cpu = next)
        ;
    rc = sched_setaffinity(current->pid, cpumask_of(cpu));
    if (rc != 0)
        pr_err("Couldn't set init affinity to cpu %d (%d)\n", cpu, rc);
}