Re: [PATCH 1/2] timer: Avoid waking up an idle-core by migrate running timer

On Tue, 31 Mar 2015, Viresh Kumar wrote:

@@ -1213,6 +1249,25 @@ static inline void __run_timers(struct tvec_base *base) call_timer_fn(timer, fn, data); spin_lock_irq(&base->lock); }

• 	/*
  

• 	 * Handler running on this base, re-queued itself on
  

• 	 * another base ?
  

• 	 */
  

• 	if (unlikely(timer->base != base)) {
  

• 		unsigned long flags;
  

• 		struct tvec_base *tbase;
  

• 		spin_unlock(&base->lock);
  

• 		tbase = lock_timer_base(timer, &flags);
  

• 		timer_clear_running(timer);
  

• 		spin_unlock(&tbase->lock);
  

• 		spin_lock(&base->lock);
  

• 	} else {
  

• 		timer_clear_running(timer);
  

• 	}
  

And just for the record:

Dereferencing timer _AFTER_ the callback function is a big NONO. The callback function is allowed to free the timer. See the comment in call_timer_fn()

Oh well,

tglx