arch/x86_64/kernel/crash.c

   1 /*
   2  * Architecture specific (x86_64) functions for kexec based crash dumps.
   3  *
   4  * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   5  *
   6  * Copyright (C) IBM Corporation, 2004. All rights reserved.
   7  *
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/types.h>
  12 #include <linux/kernel.h>
  13 #include <linux/smp.h>
  14 #include <linux/irq.h>
  15 #include <linux/reboot.h>
  16 #include <linux/kexec.h>
  17 #include <linux/delay.h>
  18 #include <linux/elf.h>
  19 #include <linux/elfcore.h>
  20 #include <linux/kdebug.h>
  21
  22 #include <asm/processor.h>
  23 #include <asm/hardirq.h>
  24 #include <asm/nmi.h>
  25 #include <asm/hw_irq.h>
  26 #include <asm/mach_apic.h>
  27
  28 /* This keeps a track of which one is crashing cpu. */
  29 static int crashing_cpu;
  30
  31 #ifdef CONFIG_SMP
  32 static atomic_t waiting_for_crash_ipi;
  33
  34 static int crash_nmi_callback(struct notifier_block *self,
  35                                 unsigned long val, void *data)
  36 {
  37         struct pt_regs *regs;
  38         int cpu;
  39
  40         if (val != DIE_NMI_IPI)
  41                 return NOTIFY_OK;
  42
  43         regs = ((struct die_args *)data)->regs;
  44         cpu = raw_smp_processor_id();
  45
  46         /*
  47          * Don't do anything if this handler is invoked on crashing cpu.
  48          * Otherwise, system will completely hang. Crashing cpu can get
  49          * an NMI if system was initially booted with nmi_watchdog parameter.
  50          */
  51         if (cpu == crashing_cpu)
  52                 return NOTIFY_STOP;
  53         local_irq_disable();
  54
  55         crash_save_cpu(regs, cpu);
  56         disable_local_APIC();
  57         atomic_dec(&waiting_for_crash_ipi);
  58         /* Assume hlt works */
  59         for(;;)
  60                 halt();
  61
  62         return 1;
  63 }
  64
  65 static void smp_send_nmi_allbutself(void)
  66 {
  67         send_IPI_allbutself(NMI_VECTOR);
  68 }
  69
  70 /*
  71  * This code is a best effort heuristic to get the
  72  * other cpus to stop executing. So races with
  73  * cpu hotplug shouldn't matter.
  74  */
  75
  76 static struct notifier_block crash_nmi_nb = {
  77         .notifier_call = crash_nmi_callback,
  78 };
  79
  80 static void nmi_shootdown_cpus(void)
  81 {
  82         unsigned long msecs;
  83
  84         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
  85         if (register_die_notifier(&crash_nmi_nb))
  86                 return;         /* return what? */
  87
  88         /*
  89          * Ensure the new callback function is set before sending
  90          * out the NMI
  91          */
  92         wmb();
  93
  94         smp_send_nmi_allbutself();
  95
  96         msecs = 1000; /* Wait at most a second for the other cpus to stop */
  97         while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
  98                 mdelay(1);
  99                 msecs--;
 100         }
 101         /* Leave the nmi callback set */
 102         disable_local_APIC();
 103 }
 104 #else
 105 static void nmi_shootdown_cpus(void)
 106 {
 107         /* There are no cpus to shootdown */
 108 }
 109 #endif
 110
 111 void machine_crash_shutdown(struct pt_regs *regs)
 112 {
 113         /*
 114          * This function is only called after the system
 115          * has panicked or is otherwise in a critical state.
 116          * The minimum amount of code to allow a kexec'd kernel
 117          * to run successfully needs to happen here.
 118          *
 119          * In practice this means shooting down the other cpus in
 120          * an SMP system.
 121          */
 122         /* The kernel is broken so disable interrupts */
 123         local_irq_disable();
 124
 125         /* Make a note of crashing cpu. Will be used in NMI callback.*/
 126         crashing_cpu = smp_processor_id();
 127         nmi_shootdown_cpus();
 128
 129         if(cpu_has_apic)
 130                  disable_local_APIC();
 131
 132         disable_IO_APIC();
 133
 134         crash_save_cpu(regs, smp_processor_id());
 135 }