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 /* boot commands */
  26 /*
  27  * Should we panic when a soft-lockup or hard-lockup occurs:
  28  */
  29 unsigned int __read_mostly hardlockup_panic =
  30                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  31 static unsigned long hardlockup_allcpu_dumped;
  32 /*
  33  * We may not want to enable hard lockup detection by default in all cases,
  34  * for example when running the kernel as a guest on a hypervisor. In these
  35  * cases this function can be called to disable hard lockup detection. This
  36  * function should only be executed once by the boot processor before the
  37  * kernel command line parameters are parsed, because otherwise it is not
  38  * possible to override this in hardlockup_panic_setup().
  39  */
  40 void hardlockup_detector_disable(void)
  41 {
  42         watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
  43 }
  44
  45 static int __init hardlockup_panic_setup(char *str)
  46 {
  47         if (!strncmp(str, "panic", 5))
  48                 hardlockup_panic = 1;
  49         else if (!strncmp(str, "nopanic", 7))
  50                 hardlockup_panic = 0;
  51         else if (!strncmp(str, "0", 1))
  52                 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
  53         else if (!strncmp(str, "1", 1))
  54                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
  55         return 1;
  56 }
  57 __setup("nmi_watchdog=", hardlockup_panic_setup);
  58
  59 void touch_nmi_watchdog(void)
  60 {
  61         /*
  62          * Using __raw here because some code paths have
  63          * preemption enabled.  If preemption is enabled
  64          * then interrupts should be enabled too, in which
  65          * case we shouldn't have to worry about the watchdog
  66          * going off.
  67          */
  68         raw_cpu_write(watchdog_nmi_touch, true);
  69         touch_softlockup_watchdog();
  70 }
  71 EXPORT_SYMBOL(touch_nmi_watchdog);
  72
  73 static struct perf_event_attr wd_hw_attr = {
  74         .type           = PERF_TYPE_HARDWARE,
  75         .config         = PERF_COUNT_HW_CPU_CYCLES,
  76         .size           = sizeof(struct perf_event_attr),
  77         .pinned         = 1,
  78         .disabled       = 1,
  79 };
  80
  81 /* Callback function for perf event subsystem */
  82 static void watchdog_overflow_callback(struct perf_event *event,
  83                  struct perf_sample_data *data,
  84                  struct pt_regs *regs)
  85 {
  86         /* Ensure the watchdog never gets throttled */
  87         event->hw.interrupts = 0;
  88
  89         if (atomic_read(&watchdog_park_in_progress) != 0)
  90                 return;
  91
  92         if (__this_cpu_read(watchdog_nmi_touch) == true) {
  93                 __this_cpu_write(watchdog_nmi_touch, false);
  94                 return;
  95         }
  96
  97         /* check for a hardlockup
  98          * This is done by making sure our timer interrupt
  99          * is incrementing.  The timer interrupt should have
 100          * fired multiple times before we overflow'd.  If it hasn't
 101          * then this is a good indication the cpu is stuck
 102          */
 103         if (is_hardlockup()) {
 104                 int this_cpu = smp_processor_id();
 105
 106                 /* only print hardlockups once */
 107                 if (__this_cpu_read(hard_watchdog_warn) == true)
 108                         return;
 109
 110                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 111                 print_modules();
 112                 print_irqtrace_events(current);
 113                 if (regs)
 114                         show_regs(regs);
 115                 else
 116                         dump_stack();
 117
 118                 /*
 119                  * Perform all-CPU dump only once to avoid multiple hardlockups
 120                  * generating interleaving traces
 121                  */
 122                 if (sysctl_hardlockup_all_cpu_backtrace &&
 123                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
 124                         trigger_allbutself_cpu_backtrace();
 125
 126                 if (hardlockup_panic)
 127                         nmi_panic(regs, "Hard LOCKUP");
 128
 129                 __this_cpu_write(hard_watchdog_warn, true);
 130                 return;
 131         }
 132
 133         __this_cpu_write(hard_watchdog_warn, false);
 134         return;
 135 }
 136
 137 /*
 138  * People like the simple clean cpu node info on boot.
 139  * Reduce the watchdog noise by only printing messages
 140  * that are different from what cpu0 displayed.
 141  */
 142 static unsigned long firstcpu_err;
 143 static atomic_t watchdog_cpus;
 144
 145 int watchdog_nmi_enable(unsigned int cpu)
 146 {
 147         struct perf_event_attr *wd_attr;
 148         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 149         int firstcpu = 0;
 150
 151         /* nothing to do if the hard lockup detector is disabled */
 152         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 153                 goto out;
 154
 155         /* is it already setup and enabled? */
 156         if (event && event->state > PERF_EVENT_STATE_OFF)
 157                 goto out;
 158
 159         /* it is setup but not enabled */
 160         if (event != NULL)
 161                 goto out_enable;
 162
 163         if (atomic_inc_return(&watchdog_cpus) == 1)
 164                 firstcpu = 1;
 165
 166         wd_attr = &wd_hw_attr;
 167         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 168
 169         /* Try to register using hardware perf events */
 170         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 171
 172         /* save the first cpu's error for future comparision */
 173         if (firstcpu && IS_ERR(event))
 174                 firstcpu_err = PTR_ERR(event);
 175
 176         if (!IS_ERR(event)) {
 177                 /* only print for the first cpu initialized */
 178                 if (firstcpu || firstcpu_err)
 179                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
 180                 goto out_save;
 181         }
 182
 183         /*
 184          * Disable the hard lockup detector if _any_ CPU fails to set up
 185          * set up the hardware perf event. The watchdog() function checks
 186          * the NMI_WATCHDOG_ENABLED bit periodically.
 187          *
 188          * The barriers are for syncing up watchdog_enabled across all the
 189          * cpus, as clear_bit() does not use barriers.
 190          */
 191         smp_mb__before_atomic();
 192         clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
 193         smp_mb__after_atomic();
 194
 195         /* skip displaying the same error again */
 196         if (!firstcpu && (PTR_ERR(event) == firstcpu_err))
 197                 return PTR_ERR(event);
 198
 199         /* vary the KERN level based on the returned errno */
 200         if (PTR_ERR(event) == -EOPNOTSUPP)
 201                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 202         else if (PTR_ERR(event) == -ENOENT)
 203                 pr_warn("disabled (cpu%i): hardware events not enabled\n",
 204                          cpu);
 205         else
 206                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 207                         cpu, PTR_ERR(event));
 208
 209         pr_info("Shutting down hard lockup detector on all cpus\n");
 210
 211         return PTR_ERR(event);
 212
 213         /* success path */
 214 out_save:
 215         per_cpu(watchdog_ev, cpu) = event;
 216 out_enable:
 217         perf_event_enable(per_cpu(watchdog_ev, cpu));
 218 out:
 219         return 0;
 220 }
 221
 222 void watchdog_nmi_disable(unsigned int cpu)
 223 {
 224         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 225
 226         if (event) {
 227                 perf_event_disable(event);
 228                 per_cpu(watchdog_ev, cpu) = NULL;
 229
 230                 /* should be in cleanup, but blocks oprofile */
 231                 perf_event_release_kernel(event);
 232
 233                 /* watchdog_nmi_enable() expects this to be zero initially. */
 234                 if (atomic_dec_and_test(&watchdog_cpus))
 235                         firstcpu_err = 0;
 236         }
 237 }