arch/sparc/kernel/nmi.c

   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/export.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 #include "kstack.h"
  27
  28 /* We don't have a real NMI on sparc64, but we can fake one
  29  * up using profiling counter overflow interrupts and interrupt
  30  * levels.
  31  *
  32  * The profile overflow interrupts at level 15, so we use
  33  * level 14 as our IRQ off level.
  34  */
  35
  36 static int panic_on_timeout;
  37
  38 /* nmi_active:
  39  * >0: the NMI watchdog is active, but can be disabled
  40  * <0: the NMI watchdog has not been set up, and cannot be enabled
  41  *  0: the NMI watchdog is disabled, but can be enabled
  42  */
  43 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  44 EXPORT_SYMBOL(nmi_active);
  45 static int nmi_init_done;
  46 static unsigned int nmi_hz = HZ;
  47 static DEFINE_PER_CPU(short, wd_enabled);
  48 static int endflag __initdata;
  49
  50 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
  51 static DEFINE_PER_CPU(long, alert_counter);
  52 static DEFINE_PER_CPU(int, nmi_touch);
  53
  54 void arch_touch_nmi_watchdog(void)
  55 {
  56         if (atomic_read(&nmi_active)) {
  57                 int cpu;
  58
  59                 for_each_present_cpu(cpu) {
  60                         if (per_cpu(nmi_touch, cpu) != 1)
  61                                 per_cpu(nmi_touch, cpu) = 1;
  62                 }
  63         }
  64 }
  65 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
  66
  67 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
  68 {
  69         int this_cpu = smp_processor_id();
  70
  71         if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
  72                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  73                 return;
  74
  75         if (do_panic || panic_on_oops)
  76                 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  77         else
  78                 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  79 }
  80
  81 notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
  82 {
  83         unsigned int sum, touched = 0;
  84         void *orig_sp;
  85
  86         clear_softint(1 << irq);
  87
  88         local_cpu_data().__nmi_count++;
  89
  90         nmi_enter();
  91
  92         orig_sp = set_hardirq_stack();
  93
  94         if (notify_die(DIE_NMI, "nmi", regs, 0,
  95                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  96                 touched = 1;
  97         else
  98                 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
  99
 100         sum = local_cpu_data().irq0_irqs;
 101         if (__this_cpu_read(nmi_touch)) {
 102                 __this_cpu_write(nmi_touch, 0);
 103                 touched = 1;
 104         }
 105         if (!touched && __this_cpu_read(last_irq_sum) == sum) {
 106                 __this_cpu_inc(alert_counter);
 107                 if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
 108                         die_nmi("BUG: NMI Watchdog detected LOCKUP",
 109                                 regs, panic_on_timeout);
 110         } else {
 111                 __this_cpu_write(last_irq_sum, sum);
 112                 __this_cpu_write(alert_counter, 0);
 113         }
 114         if (__this_cpu_read(wd_enabled)) {
 115                 pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 116                 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 117         }
 118
 119         restore_hardirq_stack(orig_sp);
 120
 121         nmi_exit();
 122 }
 123
 124 static inline unsigned int get_nmi_count(int cpu)
 125 {
 126         return cpu_data(cpu).__nmi_count;
 127 }
 128
 129 static __init void nmi_cpu_busy(void *data)
 130 {
 131         while (endflag == 0)
 132                 mb();
 133 }
 134
 135 static void report_broken_nmi(int cpu, int *prev_nmi_count)
 136 {
 137         printk(KERN_CONT "\n");
 138
 139         printk(KERN_WARNING
 140                 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 141                         cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
 142
 143         printk(KERN_WARNING
 144                 "Please report this to bugzilla.kernel.org,\n");
 145         printk(KERN_WARNING
 146                 "and attach the output of the 'dmesg' command.\n");
 147
 148         per_cpu(wd_enabled, cpu) = 0;
 149         atomic_dec(&nmi_active);
 150 }
 151
 152 void stop_nmi_watchdog(void *unused)
 153 {
 154         if (!__this_cpu_read(wd_enabled))
 155                 return;
 156         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 157         __this_cpu_write(wd_enabled, 0);
 158         atomic_dec(&nmi_active);
 159 }
 160
 161 static int __init check_nmi_watchdog(void)
 162 {
 163         unsigned int *prev_nmi_count;
 164         int cpu, err;
 165
 166         if (!atomic_read(&nmi_active))
 167                 return 0;
 168
 169         prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(unsigned int), GFP_KERNEL);
 170         if (!prev_nmi_count) {
 171                 err = -ENOMEM;
 172                 goto error;
 173         }
 174
 175         printk(KERN_INFO "Testing NMI watchdog ... ");
 176
 177         smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
 178
 179         for_each_possible_cpu(cpu)
 180                 prev_nmi_count[cpu] = get_nmi_count(cpu);
 181         local_irq_enable();
 182         mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 183
 184         for_each_online_cpu(cpu) {
 185                 if (!per_cpu(wd_enabled, cpu))
 186                         continue;
 187                 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 188                         report_broken_nmi(cpu, prev_nmi_count);
 189         }
 190         endflag = 1;
 191         if (!atomic_read(&nmi_active)) {
 192                 kfree(prev_nmi_count);
 193                 atomic_set(&nmi_active, -1);
 194                 err = -ENODEV;
 195                 goto error;
 196         }
 197         printk("OK.\n");
 198
 199         nmi_hz = 1;
 200
 201         kfree(prev_nmi_count);
 202         return 0;
 203 error:
 204         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 205         return err;
 206 }
 207
 208 void start_nmi_watchdog(void *unused)
 209 {
 210         if (__this_cpu_read(wd_enabled))
 211                 return;
 212
 213         __this_cpu_write(wd_enabled, 1);
 214         atomic_inc(&nmi_active);
 215
 216         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 217         pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 218
 219         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 220 }
 221
 222 static void nmi_adjust_hz_one(void *unused)
 223 {
 224         if (!__this_cpu_read(wd_enabled))
 225                 return;
 226
 227         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 228         pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 229
 230         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 231 }
 232
 233 void nmi_adjust_hz(unsigned int new_hz)
 234 {
 235         nmi_hz = new_hz;
 236         on_each_cpu(nmi_adjust_hz_one, NULL, 1);
 237 }
 238 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
 239
 240 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
 241 {
 242         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 243         return 0;
 244 }
 245
 246 static struct notifier_block nmi_reboot_notifier = {
 247         .notifier_call = nmi_shutdown,
 248 };
 249
 250 int __init nmi_init(void)
 251 {
 252         int err;
 253
 254         on_each_cpu(start_nmi_watchdog, NULL, 1);
 255
 256         err = check_nmi_watchdog();
 257         if (!err) {
 258                 err = register_reboot_notifier(&nmi_reboot_notifier);
 259                 if (err) {
 260                         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 261                         atomic_set(&nmi_active, -1);
 262                 }
 263         }
 264
 265         nmi_init_done = 1;
 266
 267         return err;
 268 }
 269
 270 static int __init setup_nmi_watchdog(char *str)
 271 {
 272         if (!strncmp(str, "panic", 5))
 273                 panic_on_timeout = 1;
 274
 275         return 0;
 276 }
 277 __setup("nmi_watchdog=", setup_nmi_watchdog);
 278
 279 /*
 280  * sparc specific NMI watchdog enable function.
 281  * Enables watchdog if it is not enabled already.
 282  */
 283 int watchdog_nmi_enable(unsigned int cpu)
 284 {
 285         if (atomic_read(&nmi_active) == -1) {
 286                 pr_warn("NMI watchdog cannot be enabled or disabled\n");
 287                 return -1;
 288         }
 289
 290         /*
 291          * watchdog thread could start even before nmi_init is called.
 292          * Just Return in that case. Let nmi_init finish the init
 293          * process first.
 294          */
 295         if (!nmi_init_done)
 296                 return 0;
 297
 298         smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);
 299
 300         return 0;
 301 }
 302 /*
 303  * sparc specific NMI watchdog disable function.
 304  * Disables watchdog if it is not disabled already.
 305  */
 306 void watchdog_nmi_disable(unsigned int cpu)
 307 {
 308         if (atomic_read(&nmi_active) == -1)
 309                 pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
 310         else
 311                 smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
 312 }