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 <asm/irq_regs.h>
  17 #include <linux/perf_event.h>
  18
  19 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  20 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
  21 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
  22
  23 /* boot commands */
  24 /*
  25  * Should we panic when a soft-lockup or hard-lockup occurs:
  26  */
  27 unsigned int __read_mostly hardlockup_panic =
  28                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  29 static unsigned long hardlockup_allcpu_dumped;
  30 /*
  31  * We may not want to enable hard lockup detection by default in all cases,
  32  * for example when running the kernel as a guest on a hypervisor. In these
  33  * cases this function can be called to disable hard lockup detection. This
  34  * function should only be executed once by the boot processor before the
  35  * kernel command line parameters are parsed, because otherwise it is not
  36  * possible to override this in hardlockup_panic_setup().
  37  */
  38 void hardlockup_detector_disable(void)
  39 {
  40         watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
  41 }
  42
  43 static int __init hardlockup_panic_setup(char *str)
  44 {
  45         if (!strncmp(str, "panic", 5))
  46                 hardlockup_panic = 1;
  47         else if (!strncmp(str, "nopanic", 7))
  48                 hardlockup_panic = 0;
  49         else if (!strncmp(str, "0", 1))
  50                 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
  51         else if (!strncmp(str, "1", 1))
  52                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
  53         return 1;
  54 }
  55 __setup("nmi_watchdog=", hardlockup_panic_setup);
  56
  57 void touch_nmi_watchdog(void)
  58 {
  59         /*
  60          * Using __raw here because some code paths have
  61          * preemption enabled.  If preemption is enabled
  62          * then interrupts should be enabled too, in which
  63          * case we shouldn't have to worry about the watchdog
  64          * going off.
  65          */
  66         raw_cpu_write(watchdog_nmi_touch, true);
  67         touch_softlockup_watchdog();
  68 }
  69 EXPORT_SYMBOL(touch_nmi_watchdog);
  70
  71 static struct perf_event_attr wd_hw_attr = {
  72         .type           = PERF_TYPE_HARDWARE,
  73         .config         = PERF_COUNT_HW_CPU_CYCLES,
  74         .size           = sizeof(struct perf_event_attr),
  75         .pinned         = 1,
  76         .disabled       = 1,
  77 };
  78
  79 /* Callback function for perf event subsystem */
  80 static void watchdog_overflow_callback(struct perf_event *event,
  81                  struct perf_sample_data *data,
  82                  struct pt_regs *regs)
  83 {
  84         /* Ensure the watchdog never gets throttled */
  85         event->hw.interrupts = 0;
  86
  87         if (__this_cpu_read(watchdog_nmi_touch) == true) {
  88                 __this_cpu_write(watchdog_nmi_touch, false);
  89                 return;
  90         }
  91
  92         /* check for a hardlockup
  93          * This is done by making sure our timer interrupt
  94          * is incrementing.  The timer interrupt should have
  95          * fired multiple times before we overflow'd.  If it hasn't
  96          * then this is a good indication the cpu is stuck
  97          */
  98         if (is_hardlockup()) {
  99                 int this_cpu = smp_processor_id();
 100
 101                 /* only print hardlockups once */
 102                 if (__this_cpu_read(hard_watchdog_warn) == true)
 103                         return;
 104
 105                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 106                 print_modules();
 107                 print_irqtrace_events(current);
 108                 if (regs)
 109                         show_regs(regs);
 110                 else
 111                         dump_stack();
 112
 113                 /*
 114                  * Perform all-CPU dump only once to avoid multiple hardlockups
 115                  * generating interleaving traces
 116                  */
 117                 if (sysctl_hardlockup_all_cpu_backtrace &&
 118                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
 119                         trigger_allbutself_cpu_backtrace();
 120
 121                 if (hardlockup_panic)
 122                         nmi_panic(regs, "Hard LOCKUP");
 123
 124                 __this_cpu_write(hard_watchdog_warn, true);
 125                 return;
 126         }
 127
 128         __this_cpu_write(hard_watchdog_warn, false);
 129         return;
 130 }
 131
 132 /*
 133  * People like the simple clean cpu node info on boot.
 134  * Reduce the watchdog noise by only printing messages
 135  * that are different from what cpu0 displayed.
 136  */
 137 static unsigned long cpu0_err;
 138
 139 int watchdog_nmi_enable(unsigned int cpu)
 140 {
 141         struct perf_event_attr *wd_attr;
 142         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 143
 144         /* nothing to do if the hard lockup detector is disabled */
 145         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 146                 goto out;
 147
 148         /* is it already setup and enabled? */
 149         if (event && event->state > PERF_EVENT_STATE_OFF)
 150                 goto out;
 151
 152         /* it is setup but not enabled */
 153         if (event != NULL)
 154                 goto out_enable;
 155
 156         wd_attr = &wd_hw_attr;
 157         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 158
 159         /* Try to register using hardware perf events */
 160         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 161
 162         /* save cpu0 error for future comparision */
 163         if (cpu == 0 && IS_ERR(event))
 164                 cpu0_err = PTR_ERR(event);
 165
 166         if (!IS_ERR(event)) {
 167                 /* only print for cpu0 or different than cpu0 */
 168                 if (cpu == 0 || cpu0_err)
 169                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
 170                 goto out_save;
 171         }
 172
 173         /*
 174          * Disable the hard lockup detector if _any_ CPU fails to set up
 175          * set up the hardware perf event. The watchdog() function checks
 176          * the NMI_WATCHDOG_ENABLED bit periodically.
 177          *
 178          * The barriers are for syncing up watchdog_enabled across all the
 179          * cpus, as clear_bit() does not use barriers.
 180          */
 181         smp_mb__before_atomic();
 182         clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
 183         smp_mb__after_atomic();
 184
 185         /* skip displaying the same error again */
 186         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
 187                 return PTR_ERR(event);
 188
 189         /* vary the KERN level based on the returned errno */
 190         if (PTR_ERR(event) == -EOPNOTSUPP)
 191                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 192         else if (PTR_ERR(event) == -ENOENT)
 193                 pr_warn("disabled (cpu%i): hardware events not enabled\n",
 194                          cpu);
 195         else
 196                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 197                         cpu, PTR_ERR(event));
 198
 199         pr_info("Shutting down hard lockup detector on all cpus\n");
 200
 201         return PTR_ERR(event);
 202
 203         /* success path */
 204 out_save:
 205         per_cpu(watchdog_ev, cpu) = event;
 206 out_enable:
 207         perf_event_enable(per_cpu(watchdog_ev, cpu));
 208 out:
 209         return 0;
 210 }
 211
 212 void watchdog_nmi_disable(unsigned int cpu)
 213 {
 214         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 215
 216         if (event) {
 217                 perf_event_disable(event);
 218                 per_cpu(watchdog_ev, cpu) = NULL;
 219
 220                 /* should be in cleanup, but blocks oprofile */
 221                 perf_event_release_kernel(event);
 222         }
 223         if (cpu == 0) {
 224                 /* watchdog_nmi_enable() expects this to be zero initially. */
 225                 cpu0_err = 0;
 226         }
 227 }