kernel/watchdog_hld.c

   1 /*
   2  * Detect hard lockups on a system
   3  *
   4  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   5  *
   6  * Note: Most of this code is borrowed heavily from the original softlockup
   7  * detector, so thanks to Ingo for the initial implementation.
   8  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
   9  * to those contributors as well.
  10  */
  11
  12 #define pr_fmt(fmt) "NMI watchdog: " fmt
  13
  14 #include <linux/nmi.h>
  15 #include <linux/module.h>
  16 #include <linux/sched/debug.h>
  17
  18 #include <asm/irq_regs.h>
  19 #include <linux/perf_event.h>
  20
  21 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  22 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
  23 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
  24
  25 static unsigned long hardlockup_allcpu_dumped;
  26
  27 void arch_touch_nmi_watchdog(void)
  28 {
  29         /*
  30          * Using __raw here because some code paths have
  31          * preemption enabled.  If preemption is enabled
  32          * then interrupts should be enabled too, in which
  33          * case we shouldn't have to worry about the watchdog
  34          * going off.
  35          */
  36         raw_cpu_write(watchdog_nmi_touch, true);
  37 }
  38 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
  39
  40 static struct perf_event_attr wd_hw_attr = {
  41         .type           = PERF_TYPE_HARDWARE,
  42         .config         = PERF_COUNT_HW_CPU_CYCLES,
  43         .size           = sizeof(struct perf_event_attr),
  44         .pinned         = 1,
  45         .disabled       = 1,
  46 };
  47
  48 /* Callback function for perf event subsystem */
  49 static void watchdog_overflow_callback(struct perf_event *event,
  50                  struct perf_sample_data *data,
  51                  struct pt_regs *regs)
  52 {
  53         /* Ensure the watchdog never gets throttled */
  54         event->hw.interrupts = 0;
  55
  56         if (atomic_read(&watchdog_park_in_progress) != 0)
  57                 return;
  58
  59         if (__this_cpu_read(watchdog_nmi_touch) == true) {
  60                 __this_cpu_write(watchdog_nmi_touch, false);
  61                 return;
  62         }
  63
  64         /* check for a hardlockup
  65          * This is done by making sure our timer interrupt
  66          * is incrementing.  The timer interrupt should have
  67          * fired multiple times before we overflow'd.  If it hasn't
  68          * then this is a good indication the cpu is stuck
  69          */
  70         if (is_hardlockup()) {
  71                 int this_cpu = smp_processor_id();
  72
  73                 /* only print hardlockups once */
  74                 if (__this_cpu_read(hard_watchdog_warn) == true)
  75                         return;
  76
  77                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  78                 print_modules();
  79                 print_irqtrace_events(current);
  80                 if (regs)
  81                         show_regs(regs);
  82                 else
  83                         dump_stack();
  84
  85                 /*
  86                  * Perform all-CPU dump only once to avoid multiple hardlockups
  87                  * generating interleaving traces
  88                  */
  89                 if (sysctl_hardlockup_all_cpu_backtrace &&
  90                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
  91                         trigger_allbutself_cpu_backtrace();
  92
  93                 if (hardlockup_panic)
  94                         nmi_panic(regs, "Hard LOCKUP");
  95
  96                 __this_cpu_write(hard_watchdog_warn, true);
  97                 return;
  98         }
  99
 100         __this_cpu_write(hard_watchdog_warn, false);
 101         return;
 102 }
 103
 104 /*
 105  * People like the simple clean cpu node info on boot.
 106  * Reduce the watchdog noise by only printing messages
 107  * that are different from what cpu0 displayed.
 108  */
 109 static unsigned long firstcpu_err;
 110 static atomic_t watchdog_cpus;
 111
 112 int watchdog_nmi_enable(unsigned int cpu)
 113 {
 114         struct perf_event_attr *wd_attr;
 115         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 116         int firstcpu = 0;
 117
 118         /* nothing to do if the hard lockup detector is disabled */
 119         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 120                 goto out;
 121
 122         /* is it already setup and enabled? */
 123         if (event && event->state > PERF_EVENT_STATE_OFF)
 124                 goto out;
 125
 126         /* it is setup but not enabled */
 127         if (event != NULL)
 128                 goto out_enable;
 129
 130         if (atomic_inc_return(&watchdog_cpus) == 1)
 131                 firstcpu = 1;
 132
 133         wd_attr = &wd_hw_attr;
 134         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 135
 136         /* Try to register using hardware perf events */
 137         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 138
 139         /* save the first cpu's error for future comparision */
 140         if (firstcpu && IS_ERR(event))
 141                 firstcpu_err = PTR_ERR(event);
 142
 143         if (!IS_ERR(event)) {
 144                 /* only print for the first cpu initialized */
 145                 if (firstcpu || firstcpu_err)
 146                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
 147                 goto out_save;
 148         }
 149
 150         /*
 151          * Disable the hard lockup detector if _any_ CPU fails to set up
 152          * set up the hardware perf event. The watchdog() function checks
 153          * the NMI_WATCHDOG_ENABLED bit periodically.
 154          *
 155          * The barriers are for syncing up watchdog_enabled across all the
 156          * cpus, as clear_bit() does not use barriers.
 157          */
 158         smp_mb__before_atomic();
 159         clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
 160         smp_mb__after_atomic();
 161
 162         /* skip displaying the same error again */
 163         if (!firstcpu && (PTR_ERR(event) == firstcpu_err))
 164                 return PTR_ERR(event);
 165
 166         /* vary the KERN level based on the returned errno */
 167         if (PTR_ERR(event) == -EOPNOTSUPP)
 168                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 169         else if (PTR_ERR(event) == -ENOENT)
 170                 pr_warn("disabled (cpu%i): hardware events not enabled\n",
 171                          cpu);
 172         else
 173                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 174                         cpu, PTR_ERR(event));
 175
 176         pr_info("Shutting down hard lockup detector on all cpus\n");
 177
 178         return PTR_ERR(event);
 179
 180         /* success path */
 181 out_save:
 182         per_cpu(watchdog_ev, cpu) = event;
 183 out_enable:
 184         perf_event_enable(per_cpu(watchdog_ev, cpu));
 185 out:
 186         return 0;
 187 }
 188
 189 void watchdog_nmi_disable(unsigned int cpu)
 190 {
 191         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 192
 193         if (event) {
 194                 perf_event_disable(event);
 195                 per_cpu(watchdog_ev, cpu) = NULL;
 196
 197                 /* should be in cleanup, but blocks oprofile */
 198                 perf_event_release_kernel(event);
 199
 200                 /* watchdog_nmi_enable() expects this to be zero initially. */
 201                 if (atomic_dec_and_test(&watchdog_cpus))
 202                         firstcpu_err = 0;
 203         }
 204 }