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   1 /* Pseudo NMI support on sparc64 systems.
   2  *
   3  * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
   4  *
   5  * The NMI watchdog support and infrastructure is based almost
   6  * entirely upon the x86 NMI support code.
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/param.h>
  10 #include <linux/init.h>
  11 #include <linux/percpu.h>
  12 #include <linux/nmi.h>
  13 #include <linux/module.h>
  14 #include <linux/kprobes.h>
  15 #include <linux/kernel_stat.h>
  16 #include <linux/reboot.h>
  17 #include <linux/slab.h>
  18 #include <linux/kdebug.h>
  19 #include <linux/delay.h>
  20 #include <linux/smp.h>
  21
  22 #include <asm/perf_event.h>
  23 #include <asm/ptrace.h>
  24 #include <asm/pcr.h>
  25
  26 /* We don't have a real NMI on sparc64, but we can fake one
  27  * up using profiling counter overflow interrupts and interrupt
  28  * levels.
  29  *
  30  * The profile overflow interrupts at level 15, so we use
  31  * level 14 as our IRQ off level.
  32  */
  33
  34 static int panic_on_timeout;
  35
  36 /* nmi_active:
  37  * >0: the NMI watchdog is active, but can be disabled
  38  * <0: the NMI watchdog has not been set up, and cannot be enabled
  39  *  0: the NMI watchdog is disabled, but can be enabled
  40  */
  41 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  42 EXPORT_SYMBOL(nmi_active);
  43
  44 static unsigned int nmi_hz = HZ;
  45 static DEFINE_PER_CPU(short, wd_enabled);
  46 static int endflag __initdata;
  47
  48 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
  49 static DEFINE_PER_CPU(long, alert_counter);
  50 static DEFINE_PER_CPU(int, nmi_touch);
  51
  52 void touch_nmi_watchdog(void)
  53 {
  54         if (atomic_read(&nmi_active)) {
  55                 int cpu;
  56
  57                 for_each_present_cpu(cpu) {
  58                         if (per_cpu(nmi_touch, cpu) != 1)
  59                                 per_cpu(nmi_touch, cpu) = 1;
  60                 }
  61         }
  62
  63         touch_softlockup_watchdog();
  64 }
  65 EXPORT_SYMBOL(touch_nmi_watchdog);
  66
  67 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
  68 {
  69         if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
  70                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  71                 return;
  72
  73         console_verbose();
  74         bust_spinlocks(1);
  75
  76         printk(KERN_EMERG "%s", str);
  77         printk(" on CPU%d, ip %08lx, registers:\n",
  78                smp_processor_id(), regs->tpc);
  79         show_regs(regs);
  80         dump_stack();
  81
  82         bust_spinlocks(0);
  83
  84         if (do_panic || panic_on_oops)
  85                 panic("Non maskable interrupt");
  86
  87         nmi_exit();
  88         local_irq_enable();
  89         do_exit(SIGBUS);
  90 }
  91
  92 notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
  93 {
  94         unsigned int sum, touched = 0;
  95         int cpu = smp_processor_id();
  96
  97         clear_softint(1 << irq);
  98
  99         local_cpu_data().__nmi_count++;
 100
 101         nmi_enter();
 102
 103         if (notify_die(DIE_NMI, "nmi", regs, 0,
 104                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
 105                 touched = 1;
 106         else
 107                 pcr_ops->write(PCR_PIC_PRIV);
 108
 109         sum = kstat_irqs_cpu(0, cpu);
 110         if (__get_cpu_var(nmi_touch)) {
 111                 __get_cpu_var(nmi_touch) = 0;
 112                 touched = 1;
 113         }
 114         if (!touched && __get_cpu_var(last_irq_sum) == sum) {
 115                 __this_cpu_inc(alert_counter);
 116                 if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
 117                         die_nmi("BUG: NMI Watchdog detected LOCKUP",
 118                                 regs, panic_on_timeout);
 119         } else {
 120                 __get_cpu_var(last_irq_sum) = sum;
 121                 __this_cpu_write(alert_counter, 0);
 122         }
 123         if (__get_cpu_var(wd_enabled)) {
 124                 write_pic(picl_value(nmi_hz));
 125                 pcr_ops->write(pcr_enable);
 126         }
 127
 128         nmi_exit();
 129 }
 130
 131 static inline unsigned int get_nmi_count(int cpu)
 132 {
 133         return cpu_data(cpu).__nmi_count;
 134 }
 135
 136 static __init void nmi_cpu_busy(void *data)
 137 {
 138         local_irq_enable_in_hardirq();
 139         while (endflag == 0)
 140                 mb();
 141 }
 142
 143 static void report_broken_nmi(int cpu, int *prev_nmi_count)
 144 {
 145         printk(KERN_CONT "\n");
 146
 147         printk(KERN_WARNING
 148                 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 149                         cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
 150
 151         printk(KERN_WARNING
 152                 "Please report this to bugzilla.kernel.org,\n");
 153         printk(KERN_WARNING
 154                 "and attach the output of the 'dmesg' command.\n");
 155
 156         per_cpu(wd_enabled, cpu) = 0;
 157         atomic_dec(&nmi_active);
 158 }
 159
 160 void stop_nmi_watchdog(void *unused)
 161 {
 162         pcr_ops->write(PCR_PIC_PRIV);
 163         __get_cpu_var(wd_enabled) = 0;
 164         atomic_dec(&nmi_active);
 165 }
 166
 167 static int __init check_nmi_watchdog(void)
 168 {
 169         unsigned int *prev_nmi_count;
 170         int cpu, err;
 171
 172         if (!atomic_read(&nmi_active))
 173                 return 0;
 174
 175         prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(unsigned int), GFP_KERNEL);
 176         if (!prev_nmi_count) {
 177                 err = -ENOMEM;
 178                 goto error;
 179         }
 180
 181         printk(KERN_INFO "Testing NMI watchdog ... ");
 182
 183         smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
 184
 185         for_each_possible_cpu(cpu)
 186                 prev_nmi_count[cpu] = get_nmi_count(cpu);
 187         local_irq_enable();
 188         mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 189
 190         for_each_online_cpu(cpu) {
 191                 if (!per_cpu(wd_enabled, cpu))
 192                         continue;
 193                 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 194                         report_broken_nmi(cpu, prev_nmi_count);
 195         }
 196         endflag = 1;
 197         if (!atomic_read(&nmi_active)) {
 198                 kfree(prev_nmi_count);
 199                 atomic_set(&nmi_active, -1);
 200                 err = -ENODEV;
 201                 goto error;
 202         }
 203         printk("OK.\n");
 204
 205         nmi_hz = 1;
 206
 207         kfree(prev_nmi_count);
 208         return 0;
 209 error:
 210         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 211         return err;
 212 }
 213
 214 void start_nmi_watchdog(void *unused)
 215 {
 216         __get_cpu_var(wd_enabled) = 1;
 217         atomic_inc(&nmi_active);
 218
 219         pcr_ops->write(PCR_PIC_PRIV);
 220         write_pic(picl_value(nmi_hz));
 221
 222         pcr_ops->write(pcr_enable);
 223 }
 224
 225 static void nmi_adjust_hz_one(void *unused)
 226 {
 227         if (!__get_cpu_var(wd_enabled))
 228                 return;
 229
 230         pcr_ops->write(PCR_PIC_PRIV);
 231         write_pic(picl_value(nmi_hz));
 232
 233         pcr_ops->write(pcr_enable);
 234 }
 235
 236 void nmi_adjust_hz(unsigned int new_hz)
 237 {
 238         nmi_hz = new_hz;
 239         on_each_cpu(nmi_adjust_hz_one, NULL, 1);
 240 }
 241 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
 242
 243 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
 244 {
 245         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 246         return 0;
 247 }
 248
 249 static struct notifier_block nmi_reboot_notifier = {
 250         .notifier_call = nmi_shutdown,
 251 };
 252
 253 int __init nmi_init(void)
 254 {
 255         int err;
 256
 257         on_each_cpu(start_nmi_watchdog, NULL, 1);
 258
 259         err = check_nmi_watchdog();
 260         if (!err) {
 261                 err = register_reboot_notifier(&nmi_reboot_notifier);
 262                 if (err) {
 263                         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 264                         atomic_set(&nmi_active, -1);
 265                 }
 266         }
 267         if (!err)
 268                 init_hw_perf_events();
 269
 270         return err;
 271 }
 272
 273 static int __init setup_nmi_watchdog(char *str)
 274 {
 275         if (!strncmp(str, "panic", 5))
 276                 panic_on_timeout = 1;
 277
 278         return 0;
 279 }
 280 __setup("nmi_watchdog=", setup_nmi_watchdog);