kernel/nmi_watchdog.c

   1 /*
   2  * Detect Hard Lockups using the NMI
   3  *
   4  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   5  *
   6  * this code detects hard lockups: incidents in where on a CPU
   7  * the kernel does not respond to anything except NMI.
   8  *
   9  * Note: Most of this code is borrowed heavily from softlockup.c,
  10  * so thanks to Ingo for the initial implementation.
  11  * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
  12  * to those contributors as well.
  13  */
  14
  15 #include <linux/mm.h>
  16 #include <linux/cpu.h>
  17 #include <linux/nmi.h>
  18 #include <linux/init.h>
  19 #include <linux/delay.h>
  20 #include <linux/freezer.h>
  21 #include <linux/lockdep.h>
  22 #include <linux/notifier.h>
  23 #include <linux/module.h>
  24 #include <linux/sysctl.h>
  25
  26 #include <asm/irq_regs.h>
  27 #include <linux/perf_event.h>
  28
  29 static DEFINE_PER_CPU(struct perf_event *, nmi_watchdog_ev);
  30 static DEFINE_PER_CPU(int, nmi_watchdog_touch);
  31 static DEFINE_PER_CPU(long, alert_counter);
  32
  33 static int panic_on_timeout;
  34
  35 void touch_nmi_watchdog(void)
  36 {
  37         __raw_get_cpu_var(nmi_watchdog_touch) = 1;
  38         touch_softlockup_watchdog();
  39 }
  40 EXPORT_SYMBOL(touch_nmi_watchdog);
  41
  42 void touch_all_nmi_watchdog(void)
  43 {
  44         int cpu;
  45
  46         for_each_online_cpu(cpu)
  47                 per_cpu(nmi_watchdog_touch, cpu) = 1;
  48         touch_softlockup_watchdog();
  49 }
  50
  51 static int __init setup_nmi_watchdog(char *str)
  52 {
  53         if (!strncmp(str, "panic", 5)) {
  54                 panic_on_timeout = 1;
  55                 str = strchr(str, ',');
  56                 if (!str)
  57                         return 1;
  58                 ++str;
  59         }
  60         return 1;
  61 }
  62 __setup("nmi_watchdog=", setup_nmi_watchdog);
  63
  64 struct perf_event_attr wd_hw_attr = {
  65         .type           = PERF_TYPE_HARDWARE,
  66         .config         = PERF_COUNT_HW_CPU_CYCLES,
  67         .size           = sizeof(struct perf_event_attr),
  68         .pinned         = 1,
  69         .disabled       = 1,
  70 };
  71
  72 struct perf_event_attr wd_sw_attr = {
  73         .type           = PERF_TYPE_SOFTWARE,
  74         .config         = PERF_COUNT_SW_CPU_CLOCK,
  75         .size           = sizeof(struct perf_event_attr),
  76         .pinned         = 1,
  77         .disabled       = 1,
  78 };
  79
  80 void wd_overflow(struct perf_event *event, int nmi,
  81                  struct perf_sample_data *data,
  82                  struct pt_regs *regs)
  83 {
  84         int cpu = smp_processor_id();
  85         int touched = 0;
  86
  87         if (__get_cpu_var(nmi_watchdog_touch)) {
  88                 per_cpu(nmi_watchdog_touch, cpu) = 0;
  89                 touched = 1;
  90         }
  91
  92         /* check to see if the cpu is doing anything */
  93         if (!touched && hw_nmi_is_cpu_stuck(regs)) {
  94                 /*
  95                  * Ayiee, looks like this CPU is stuck ...
  96                  * wait a few IRQs (5 seconds) before doing the oops ...
  97                  */
  98                 per_cpu(alert_counter, cpu) += 1;
  99                 if (per_cpu(alert_counter, cpu) == 5) {
 100                         if (panic_on_timeout)
 101                                 panic("NMI Watchdog detected LOCKUP on cpu %d", cpu);
 102                         else
 103                                 WARN(1, "NMI Watchdog detected LOCKUP on cpu %d", cpu);
 104                 }
 105         } else {
 106                 per_cpu(alert_counter, cpu) = 0;
 107         }
 108
 109         return;
 110 }
 111
 112 static int enable_nmi_watchdog(int cpu)
 113 {
 114         struct perf_event *event;
 115         struct perf_event_attr *wd_attr;
 116
 117         event = per_cpu(nmi_watchdog_ev, cpu);
 118         if (event && event->state > PERF_EVENT_STATE_OFF)
 119                 return 0;
 120
 121         if (event == NULL) {
 122                 /* Try to register using hardware perf events first */
 123                 wd_attr = &wd_hw_attr;
 124                 wd_attr->sample_period = hw_nmi_get_sample_period();
 125                 event = perf_event_create_kernel_counter(wd_attr, cpu, -1, wd_overflow);
 126                 if (IS_ERR(event)) {
 127                         /* hardware doesn't exist or not supported, fallback to software events */
 128                         printk(KERN_INFO "nmi_watchdog: hardware not available, trying software events\n");
 129                         wd_attr = &wd_sw_attr;
 130                         wd_attr->sample_period = NSEC_PER_SEC;
 131                         event = perf_event_create_kernel_counter(wd_attr, cpu, -1, wd_overflow);
 132                         if (IS_ERR(event)) {
 133                                 printk(KERN_ERR "nmi watchdog failed to create perf event on %i: %p\n", cpu, event);
 134                                 return -1;
 135                         }
 136                 }
 137                 per_cpu(nmi_watchdog_ev, cpu) = event;
 138         }
 139         perf_event_enable(per_cpu(nmi_watchdog_ev, cpu));
 140         return 0;
 141 }
 142
 143 static void disable_nmi_watchdog(int cpu)
 144 {
 145         struct perf_event *event;
 146
 147         event = per_cpu(nmi_watchdog_ev, cpu);
 148         if (event) {
 149                 perf_event_disable(per_cpu(nmi_watchdog_ev, cpu));
 150                 per_cpu(nmi_watchdog_ev, cpu) = NULL;
 151                 perf_event_release_kernel(event);
 152         }
 153 }
 154
 155 #ifdef CONFIG_SYSCTL
 156 /*
 157  * proc handler for /proc/sys/kernel/nmi_watchdog
 158  */
 159 int nmi_watchdog_enabled;
 160
 161 int proc_nmi_enabled(struct ctl_table *table, int write,
 162                      void __user *buffer, size_t *length, loff_t *ppos)
 163 {
 164         int cpu;
 165
 166         if (!write) {
 167                 struct perf_event *event;
 168                 for_each_online_cpu(cpu) {
 169                         event = per_cpu(nmi_watchdog_ev, cpu);
 170                         if (event && event->state > PERF_EVENT_STATE_OFF) {
 171                                 nmi_watchdog_enabled = 1;
 172                                 break;
 173                         }
 174                 }
 175                 proc_dointvec(table, write, buffer, length, ppos);
 176                 return 0;
 177         }
 178
 179         touch_all_nmi_watchdog();
 180         proc_dointvec(table, write, buffer, length, ppos);
 181         if (nmi_watchdog_enabled) {
 182                 for_each_online_cpu(cpu)
 183                         if (enable_nmi_watchdog(cpu)) {
 184                                 printk(KERN_ERR "NMI watchdog failed configuration, "
 185                                         " can not be enabled\n");
 186                         }
 187         } else {
 188                 for_each_online_cpu(cpu)
 189                         disable_nmi_watchdog(cpu);
 190         }
 191         return 0;
 192 }
 193
 194 #endif /* CONFIG_SYSCTL */
 195
 196 /*
 197  * Create/destroy watchdog threads as CPUs come and go:
 198  */
 199 static int __cpuinit
 200 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 201 {
 202         int hotcpu = (unsigned long)hcpu;
 203
 204         switch (action) {
 205         case CPU_UP_PREPARE:
 206         case CPU_UP_PREPARE_FROZEN:
 207                 per_cpu(nmi_watchdog_touch, hotcpu) = 0;
 208                 break;
 209         case CPU_ONLINE:
 210         case CPU_ONLINE_FROZEN:
 211                 if (enable_nmi_watchdog(hotcpu))
 212                         return NOTIFY_BAD;
 213                 break;
 214 #ifdef CONFIG_HOTPLUG_CPU
 215         case CPU_UP_CANCELED:
 216         case CPU_UP_CANCELED_FROZEN:
 217                 disable_nmi_watchdog(hotcpu);
 218         case CPU_DEAD:
 219         case CPU_DEAD_FROZEN:
 220                 break;
 221 #endif /* CONFIG_HOTPLUG_CPU */
 222         }
 223         return NOTIFY_OK;
 224 }
 225
 226 static struct notifier_block __cpuinitdata cpu_nfb = {
 227         .notifier_call = cpu_callback
 228 };
 229
 230 static int __initdata nonmi_watchdog;
 231
 232 static int __init nonmi_watchdog_setup(char *str)
 233 {
 234         nonmi_watchdog = 1;
 235         return 1;
 236 }
 237 __setup("nonmi_watchdog", nonmi_watchdog_setup);
 238
 239 static int __init spawn_nmi_watchdog_task(void)
 240 {
 241         void *cpu = (void *)(long)smp_processor_id();
 242         int err;
 243
 244         if (nonmi_watchdog)
 245                 return 0;
 246
 247         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 248         if (err == NOTIFY_BAD) {
 249                 BUG();
 250                 return 1;
 251         }
 252         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 253         register_cpu_notifier(&cpu_nfb);
 254
 255         return 0;
 256 }
 257 early_initcall(spawn_nmi_watchdog_task);