/*
   * Detect Soft Lockups
   *

   * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc.

   *
   * this code detects soft lockups: incidents in where on a CPU
   * the kernel does not reschedule for 10 seconds or more.
   */

  #include <linux/mm.h>
  #include <linux/cpu.h>

  #include <linux/nmi.h>

  #include <linux/init.h>
  #include <linux/delay.h>

  #include <linux/freezer.h>

  #include <linux/kthread.h>

  #include <linux/lockdep.h>

  #include <linux/notifier.h>
  #include <linux/module.h>

  #include <linux/sysctl.h>

  #include <asm/irq_regs.h>

  static DEFINE_SPINLOCK(print_lock);

  static DEFINE_PER_CPU(unsigned long, softlockup_touch_ts); /* touch timestamp */
  static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */
  static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);

  static DEFINE_PER_CPU(bool, softlock_touch_sync);

  static int __read_mostly did_panic;

  int __read_mostly softlockup_thresh = 60;

  /*
   * Should we panic (and reboot, if panic_timeout= is set) when a
   * soft-lockup occurs:
   */
  unsigned int __read_mostly softlockup_panic =
  				CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
  
  static int __init softlockup_panic_setup(char *str)
  {
  	softlockup_panic = simple_strtoul(str, NULL, 0);
  
  	return 1;
  }
  __setup("softlockup_panic=", softlockup_panic_setup);

  static int
  softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)

  {
  	did_panic = 1;
  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block panic_block = {
  	.notifier_call = softlock_panic,
  };

  /*
   * Returns seconds, approximately.  We don't need nanosecond
   * resolution, and we don't need to waste time with a big divide when
   * 2^30ns == 1.074s.
   */

  static unsigned long get_timestamp(int this_cpu)

  {

  	return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */

  }

  static void __touch_softlockup_watchdog(void)

  {

  	int this_cpu = raw_smp_processor_id();

  	__raw_get_cpu_var(softlockup_touch_ts) = get_timestamp(this_cpu);

  }

  
  void touch_softlockup_watchdog(void)
  {

  	__raw_get_cpu_var(softlockup_touch_ts) = 0;

  }

  EXPORT_SYMBOL(touch_softlockup_watchdog);

  void touch_softlockup_watchdog_sync(void)
  {
  	__raw_get_cpu_var(softlock_touch_sync) = true;
  	__raw_get_cpu_var(softlockup_touch_ts) = 0;
  }

  void touch_all_softlockup_watchdogs(void)
  {
  	int cpu;
  
  	/* Cause each CPU to re-update its timestamp rather than complain */
  	for_each_online_cpu(cpu)

  		per_cpu(softlockup_touch_ts, cpu) = 0;

  }
  EXPORT_SYMBOL(touch_all_softlockup_watchdogs);

  int proc_dosoftlockup_thresh(struct ctl_table *table, int write,

  			     void __user *buffer,

  			     size_t *lenp, loff_t *ppos)
  {
  	touch_all_softlockup_watchdogs();

  	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);

  }

  /*
   * This callback runs from the timer interrupt, and checks
   * whether the watchdog thread has hung or not:
   */

  void softlockup_tick(void)

  {
  	int this_cpu = smp_processor_id();

  	unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu);
  	unsigned long print_ts;

  	struct pt_regs *regs = get_irq_regs();

  	unsigned long now;

  	/* Is detection switched off? */

  	if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) {

  		/* Be sure we don't false trigger if switched back on */

  		if (touch_ts)
  			per_cpu(softlockup_touch_ts, this_cpu) = 0;

  		return;
  	}

  	if (touch_ts == 0) {

  		if (unlikely(per_cpu(softlock_touch_sync, this_cpu))) {
  			/*
  			 * If the time stamp was touched atomically
  			 * make sure the scheduler tick is up to date.
  			 */
  			per_cpu(softlock_touch_sync, this_cpu) = false;
  			sched_clock_tick();
  		}

  		__touch_softlockup_watchdog();

  		return;

  	}

  	print_ts = per_cpu(softlockup_print_ts, this_cpu);

  
  	/* report at most once a second */

  	if (print_ts == touch_ts || did_panic)

  		return;

  	/* do not print during early bootup: */
  	if (unlikely(system_state != SYSTEM_RUNNING)) {

  		__touch_softlockup_watchdog();

  		return;

  	}

  	now = get_timestamp(this_cpu);

  	/*
  	 * Wake up the high-prio watchdog task twice per
  	 * threshold timespan.
  	 */

  	if (time_after(now - softlockup_thresh/2, touch_ts))

  		wake_up_process(per_cpu(softlockup_watchdog, this_cpu));

  	/* Warn about unreasonable delays: */

  	if (time_before_eq(now - softlockup_thresh, touch_ts))

  		return;

  	per_cpu(softlockup_print_ts, this_cpu) = touch_ts;

  
  	spin_lock(&print_lock);

  	printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]
  ",

  			this_cpu, now - touch_ts,

  			current->comm, task_pid_nr(current));

  	print_modules();

  	print_irqtrace_events(current);

  	if (regs)
  		show_regs(regs);
  	else

  		dump_stack();

  	spin_unlock(&print_lock);

  
  	if (softlockup_panic)
  		panic("softlockup: hung tasks");

  }
  
  /*
   * The watchdog thread - runs every second and touches the timestamp.
   */

  static int watchdog(void *__bind_cpu)

  {

  	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

  
  	sched_setscheduler(current, SCHED_FIFO, &param);

  	/* initialize timestamp */

  	__touch_softlockup_watchdog();

  	set_current_state(TASK_INTERRUPTIBLE);

  	/*

  	 * Run briefly once per second to reset the softlockup timestamp.

  	 * If this gets delayed for more than 60 seconds then the

  	 * debug-printout triggers in softlockup_tick().

  	 */
  	while (!kthread_should_stop()) {

  		__touch_softlockup_watchdog();

  		schedule();
  
  		if (kthread_should_stop())
  			break;

  		set_current_state(TASK_INTERRUPTIBLE);

  	}

  	__set_current_state(TASK_RUNNING);

  
  	return 0;
  }
  
  /*
   * Create/destroy watchdog threads as CPUs come and go:
   */

  static int __cpuinit

  cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
  {
  	int hotcpu = (unsigned long)hcpu;
  	struct task_struct *p;
  
  	switch (action) {
  	case CPU_UP_PREPARE:

  	case CPU_UP_PREPARE_FROZEN:

  		BUG_ON(per_cpu(softlockup_watchdog, hotcpu));

  		p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
  		if (IS_ERR(p)) {

  			printk(KERN_ERR "watchdog for %i failed
  ", hotcpu);

  			return NOTIFY_BAD;
  		}

  		per_cpu(softlockup_touch_ts, hotcpu) = 0;
  		per_cpu(softlockup_watchdog, hotcpu) = p;

  		kthread_bind(p, hotcpu);

  		break;

  	case CPU_ONLINE:

  	case CPU_ONLINE_FROZEN:

  		wake_up_process(per_cpu(softlockup_watchdog, hotcpu));

  		break;
  #ifdef CONFIG_HOTPLUG_CPU

  	case CPU_UP_CANCELED:
  	case CPU_UP_CANCELED_FROZEN:

  		if (!per_cpu(softlockup_watchdog, hotcpu))

  			break;
  		/* Unbind so it can run.  Fall thru. */

  		kthread_bind(per_cpu(softlockup_watchdog, hotcpu),

  			     cpumask_any(cpu_online_mask));

  	case CPU_DEAD:

  	case CPU_DEAD_FROZEN:

  		p = per_cpu(softlockup_watchdog, hotcpu);
  		per_cpu(softlockup_watchdog, hotcpu) = NULL;

  		kthread_stop(p);
  		break;
  #endif /* CONFIG_HOTPLUG_CPU */

  	}

  	return NOTIFY_OK;
  }

  static struct notifier_block __cpuinitdata cpu_nfb = {

  	.notifier_call = cpu_callback
  };

  static int __initdata nosoftlockup;
  
  static int __init nosoftlockup_setup(char *str)
  {
  	nosoftlockup = 1;
  	return 1;
  }
  __setup("nosoftlockup", nosoftlockup_setup);
  
  static int __init spawn_softlockup_task(void)

  {
  	void *cpu = (void *)(long)smp_processor_id();

  	int err;

  	if (nosoftlockup)
  		return 0;
  
  	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
  	if (err == NOTIFY_BAD) {
  		BUG();
  		return 1;
  	}

  	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
  	register_cpu_notifier(&cpu_nfb);

  	atomic_notifier_chain_register(&panic_notifier_list, &panic_block);

  
  	return 0;

  }

  early_initcall(spawn_softlockup_task);