Linux 内核时钟之经典timer处理

/*
 * This function runs timers and the timer-tq in bottom half context.
 */
static __latent_entropy void run_timer_softirq(struct softirq_action *h)
{
 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 __run_timers(base);
 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active)
  __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
}

/**
 * __run_timers - run all expired timers (if any) on this CPU.
 * @base: the timer vector to be processed.
 */
static inline void __run_timers(struct timer_base *base)
{
 struct hlist_head heads[LVL_DEPTH];
 int levels;
 if (!time_after_eq(jiffies, base->clk))
  return;
 spin_lock_irq(&base->lock);
 while (time_after_eq(jiffies, base->clk)) {
  levels = collect_expired_timers(base, heads);
  base->clk++;
  while (levels--)
   expire_timers(base, heads + levels);
 }
 base->running_timer = NULL;
 spin_unlock_irq(&base->lock);
}
 
static void expire_timers(struct timer_base *base, struct hlist_head *head)
{
 while (!hlist_empty(head)) {
  struct timer_list *timer;
  void (*fn)(unsigned long);
  unsigned long data;
  timer = hlist_entry(head->first, struct timer_list, entry);
  timer_stats_account_timer(timer);
  base->running_timer = timer;
  detach_timer(timer, true);
  fn = timer->function;
  data = timer->data;
  if (timer->flags & TIMER_IRQSAFE) {
   spin_unlock(&base->lock);
   call_timer_fn(timer, fn, data);
   spin_lock(&base->lock);
  } else {
   spin_unlock_irq(&base->lock);
   call_timer_fn(timer, fn, data);
   spin_lock_irq(&base->lock);
  }
 }
}
 

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