arch/sparc/kernel/nmi.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Pseudo NMI support on sparc64 systems.
   3  *
   4  * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
   5  *
   6  * The NMI watchdog support and infrastructure is based almost
   7  * entirely upon the x86 NMI support code.
   8  */
   9 #include <linux/kernel.h>
  10 #include <linux/param.h>
  11 #include <linux/init.h>
  12 #include <linux/percpu.h>
  13 #include <linux/nmi.h>
  14 #include <linux/export.h>
  15 #include <linux/kprobes.h>
  16 #include <linux/kernel_stat.h>
  17 #include <linux/reboot.h>
  18 #include <linux/slab.h>
  19 #include <linux/kdebug.h>
  20 #include <linux/delay.h>
  21 #include <linux/smp.h>
  22
  23 #include <asm/perf_event.h>
  24 #include <asm/ptrace.h>
  25 #include <asm/pcr.h>
  26
  27 #include "kstack.h"
  28
  29 /* We don't have a real NMI on sparc64, but we can fake one
  30  * up using profiling counter overflow interrupts and interrupt
  31  * levels.
  32  *
  33  * The profile overflow interrupts at level 15, so we use
  34  * level 14 as our IRQ off level.
  35  */
  36
  37 static int panic_on_timeout;
  38
  39 /* nmi_active:
  40  * >0: the NMI watchdog is active, but can be disabled
  41  * <0: the NMI watchdog has not been set up, and cannot be enabled
  42  *  0: the NMI watchdog is disabled, but can be enabled
  43  */
  44 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  45 EXPORT_SYMBOL(nmi_active);
  46 static int nmi_init_done;
  47 static unsigned int nmi_hz = HZ;
  48 static DEFINE_PER_CPU(short, wd_enabled);
  49 static int endflag __initdata;
  50
  51 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
  52 static DEFINE_PER_CPU(long, alert_counter);
  53 static DEFINE_PER_CPU(int, nmi_touch);
  54
  55 void arch_touch_nmi_watchdog(void)
  56 {
  57         if (atomic_read(&nmi_active)) {
  58                 int cpu;
  59
  60                 for_each_present_cpu(cpu) {
  61                         if (per_cpu(nmi_touch, cpu) != 1)
  62                                 per_cpu(nmi_touch, cpu) = 1;
  63                 }
  64         }
  65 }
  66 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
  67
  68 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
  69 {
  70         int this_cpu = smp_processor_id();
  71
  72         if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
  73                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  74                 return;
  75
  76         if (do_panic || panic_on_oops)
  77                 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  78         else
  79                 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  80 }
  81
  82 notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
  83 {
  84         unsigned int sum, touched = 0;
  85         void *orig_sp;
  86
  87         clear_softint(1 << irq);
  88
  89         local_cpu_data().__nmi_count++;
  90
  91         nmi_enter();
  92
  93         orig_sp = set_hardirq_stack();
  94
  95         if (notify_die(DIE_NMI, "nmi", regs, 0,
  96                        pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  97                 touched = 1;
  98         else
  99                 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 100
 101         sum = local_cpu_data().irq0_irqs;
 102         if (__this_cpu_read(nmi_touch)) {
 103                 __this_cpu_write(nmi_touch, 0);
 104                 touched = 1;
 105         }
 106         if (!touched && __this_cpu_read(last_irq_sum) == sum) {
 107                 __this_cpu_inc(alert_counter);
 108                 if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
 109                         die_nmi("BUG: NMI Watchdog detected LOCKUP",
 110                                 regs, panic_on_timeout);
 111         } else {
 112                 __this_cpu_write(last_irq_sum, sum);
 113                 __this_cpu_write(alert_counter, 0);
 114         }
 115         if (__this_cpu_read(wd_enabled)) {
 116                 pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 117                 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 118         }
 119
 120         restore_hardirq_stack(orig_sp);
 121
 122         nmi_exit();
 123 }
 124
 125 static inline unsigned int get_nmi_count(int cpu)
 126 {
 127         return cpu_data(cpu).__nmi_count;
 128 }
 129
 130 static __init void nmi_cpu_busy(void *data)
 131 {
 132         while (endflag == 0)
 133                 mb();
 134 }
 135
 136 static void report_broken_nmi(int cpu, int *prev_nmi_count)
 137 {
 138         printk(KERN_CONT "\n");
 139
 140         printk(KERN_WARNING
 141                 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 142                         cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
 143
 144         printk(KERN_WARNING
 145                 "Please report this to bugzilla.kernel.org,\n");
 146         printk(KERN_WARNING
 147                 "and attach the output of the 'dmesg' command.\n");
 148
 149         per_cpu(wd_enabled, cpu) = 0;
 150         atomic_dec(&nmi_active);
 151 }
 152
 153 void stop_nmi_watchdog(void *unused)
 154 {
 155         if (!__this_cpu_read(wd_enabled))
 156                 return;
 157         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 158         __this_cpu_write(wd_enabled, 0);
 159         atomic_dec(&nmi_active);
 160 }
 161
 162 static int __init check_nmi_watchdog(void)
 163 {
 164         unsigned int *prev_nmi_count;
 165         int cpu, err;
 166
 167         if (!atomic_read(&nmi_active))
 168                 return 0;
 169
 170         prev_nmi_count = kmalloc_array(nr_cpu_ids, sizeof(unsigned int),
 171                                        GFP_KERNEL);
 172         if (!prev_nmi_count) {
 173                 err = -ENOMEM;
 174                 goto error;
 175         }
 176
 177         printk(KERN_INFO "Testing NMI watchdog ... ");
 178
 179         smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
 180
 181         for_each_possible_cpu(cpu)
 182                 prev_nmi_count[cpu] = get_nmi_count(cpu);
 183         local_irq_enable();
 184         mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 185
 186         for_each_online_cpu(cpu) {
 187                 if (!per_cpu(wd_enabled, cpu))
 188                         continue;
 189                 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 190                         report_broken_nmi(cpu, prev_nmi_count);
 191         }
 192         endflag = 1;
 193         if (!atomic_read(&nmi_active)) {
 194                 kfree(prev_nmi_count);
 195                 atomic_set(&nmi_active, -1);
 196                 err = -ENODEV;
 197                 goto error;
 198         }
 199         printk("OK.\n");
 200
 201         nmi_hz = 1;
 202
 203         kfree(prev_nmi_count);
 204         return 0;
 205 error:
 206         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 207         return err;
 208 }
 209
 210 void start_nmi_watchdog(void *unused)
 211 {
 212         if (__this_cpu_read(wd_enabled))
 213                 return;
 214
 215         __this_cpu_write(wd_enabled, 1);
 216         atomic_inc(&nmi_active);
 217
 218         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 219         pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 220
 221         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 222 }
 223
 224 static void nmi_adjust_hz_one(void *unused)
 225 {
 226         if (!__this_cpu_read(wd_enabled))
 227                 return;
 228
 229         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
 230         pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
 231
 232         pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
 233 }
 234
 235 void nmi_adjust_hz(unsigned int new_hz)
 236 {
 237         nmi_hz = new_hz;
 238         on_each_cpu(nmi_adjust_hz_one, NULL, 1);
 239 }
 240 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
 241
 242 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
 243 {
 244         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 245         return 0;
 246 }
 247
 248 static struct notifier_block nmi_reboot_notifier = {
 249         .notifier_call = nmi_shutdown,
 250 };
 251
 252 int __init nmi_init(void)
 253 {
 254         int err;
 255
 256         on_each_cpu(start_nmi_watchdog, NULL, 1);
 257
 258         err = check_nmi_watchdog();
 259         if (!err) {
 260                 err = register_reboot_notifier(&nmi_reboot_notifier);
 261                 if (err) {
 262                         on_each_cpu(stop_nmi_watchdog, NULL, 1);
 263                         atomic_set(&nmi_active, -1);
 264                 }
 265         }
 266
 267         nmi_init_done = 1;
 268
 269         return err;
 270 }
 271
 272 static int __init setup_nmi_watchdog(char *str)
 273 {
 274         if (!strncmp(str, "panic", 5))
 275                 panic_on_timeout = 1;
 276
 277         return 0;
 278 }
 279 __setup("nmi_watchdog=", setup_nmi_watchdog);
 280
 281 /*
 282  * sparc specific NMI watchdog enable function.
 283  * Enables watchdog if it is not enabled already.
 284  */
 285 int watchdog_nmi_enable(unsigned int cpu)
 286 {
 287         if (atomic_read(&nmi_active) == -1) {
 288                 pr_warn("NMI watchdog cannot be enabled or disabled\n");
 289                 return -1;
 290         }
 291
 292         /*
 293          * watchdog thread could start even before nmi_init is called.
 294          * Just Return in that case. Let nmi_init finish the init
 295          * process first.
 296          */
 297         if (!nmi_init_done)
 298                 return 0;
 299
 300         smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);
 301
 302         return 0;
 303 }
 304 /*
 305  * sparc specific NMI watchdog disable function.
 306  * Disables watchdog if it is not disabled already.
 307  */
 308 void watchdog_nmi_disable(unsigned int cpu)
 309 {
 310         if (atomic_read(&nmi_active) == -1)
 311                 pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
 312         else
 313                 smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
 314 }