root/arch/x86/kernel/crash.c

DEFINITIONS

1. crash_nmi_callback
2. smp_send_nmi_allbutself
3. nmi_shootdown_cpus
4. nmi_shootdown_cpus
5. native_machine_crash_shutdown

/*
 * Architecture specific (i386/x86_64) functions for kexec based crash dumps.
 *
 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *
 * Copyright (C) IBM Corporation, 2004. All rights reserved.
 *
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/elf.h>
#include <linux/elfcore.h>

#include <asm/processor.h>
#include <asm/hardirq.h>
#include <asm/nmi.h>
#include <asm/hw_irq.h>
#include <asm/apic.h>
#include <asm/hpet.h>
#include <linux/kdebug.h>
#include <asm/smp.h>
#include <asm/reboot.h>

#include <mach_ipi.h>

/* This keeps a track of which one is crashing cpu. */
static int crashing_cpu;

#if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
static atomic_t waiting_for_crash_ipi;

static int crash_nmi_callback(struct notifier_block *self,
                        unsigned long val, void *data)
{
        struct pt_regs *regs;
#ifdef CONFIG_X86_32
        struct pt_regs fixed_regs;
#endif
        int cpu;

        if (val != DIE_NMI_IPI)
                return NOTIFY_OK;

        regs = ((struct die_args *)data)->regs;
        cpu = raw_smp_processor_id();

        /* Don't do anything if this handler is invoked on crashing cpu.
         * Otherwise, system will completely hang. Crashing cpu can get
         * an NMI if system was initially booted with nmi_watchdog parameter.
         */
        if (cpu == crashing_cpu)
                return NOTIFY_STOP;
        local_irq_disable();

#ifdef CONFIG_X86_32
        if (!user_mode_vm(regs)) {
                crash_fixup_ss_esp(&fixed_regs, regs);
                regs = &fixed_regs;
        }
#endif
        crash_save_cpu(regs, cpu);
        disable_local_APIC();
        atomic_dec(&waiting_for_crash_ipi);
        /* Assume hlt works */
        halt();
        for (;;)
                cpu_relax();

        return 1;
}

static void smp_send_nmi_allbutself(void)
{
        cpumask_t mask = cpu_online_map;
        cpu_clear(safe_smp_processor_id(), mask);
        if (!cpus_empty(mask))
                send_IPI_mask(mask, NMI_VECTOR);
}

static struct notifier_block crash_nmi_nb = {
        .notifier_call = crash_nmi_callback,
};

static void nmi_shootdown_cpus(void)
{
        unsigned long msecs;

        atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
        /* Would it be better to replace the trap vector here? */
        if (register_die_notifier(&crash_nmi_nb))
                return;         /* return what? */
        /* Ensure the new callback function is set before sending
         * out the NMI
         */
        wmb();

        smp_send_nmi_allbutself();

        msecs = 1000; /* Wait at most a second for the other cpus to stop */
        while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
                mdelay(1);
                msecs--;
        }

        /* Leave the nmi callback set */
        disable_local_APIC();
}
#else
static void nmi_shootdown_cpus(void)
{
        /* There are no cpus to shootdown */
}
#endif

void native_machine_crash_shutdown(struct pt_regs *regs)
{
        /* This function is only called after the system
         * has panicked or is otherwise in a critical state.
         * The minimum amount of code to allow a kexec'd kernel
         * to run successfully needs to happen here.
         *
         * In practice this means shooting down the other cpus in
         * an SMP system.
         */
        /* The kernel is broken so disable interrupts */
        local_irq_disable();

        /* Make a note of crashing cpu. Will be used in NMI callback.*/
        crashing_cpu = safe_smp_processor_id();
        nmi_shootdown_cpus();
        lapic_shutdown();
#if defined(CONFIG_X86_IO_APIC)
        disable_IO_APIC();
#endif
#ifdef CONFIG_HPET_TIMER
        hpet_disable();
#endif
        crash_save_cpu(regs, safe_smp_processor_id());
}