Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 02 Apr 2005 15:02:33 +0400 | From | Oleg Nesterov <> | Subject | Re: [RFC][PATCH] timers fixes/improvements |
| |
Andrew Morton wrote: > > Oleg Nesterov <oleg@tv-sign.ru> wrote: > > > > +void fastcall init_timer(struct timer_list *timer) > > +{ > > + timer->entry.next = NULL; > > + timer->_base = &per_cpu(tvec_bases, > > + __smp_processor_id()).t_base; > > + timer->magic = TIMER_MAGIC; > > +} > > __smp_processor_id() is not implemented on all architectures. I'll switch > this to _smp_processor_id().
Wow, I did not know.
> It's a rather odd thing which you're doing there. Why does a > not-yet-scheduled timer need a ->_base?
Because all locking goes through timer_list->base->lock now. That is why timer_list->lock can be deleted. The timer is always locked via loc_timer_base().
timer->base == NULL only temporally when __mod_timer() does while switching timer's base: base = lock_timer_base(timer); timer->base = NULL; unlock(base->lock); // Nobody can use this timer, lock_timer_base() // will spin waiting for ->base != 0 lock(new_base->lock); timer->base = new_base; unlock(new_base);
So ->base == NULL means that timer itself is locked, not it's base. That is why __mod_timer() do not need to hold 2 spinlocks at once.
Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| ![\](/images/icornerr.gif) |