On Fri, 2 Mar 2007 15:23:08 +0100 Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote: > On Fri, Mar 02, 2007 at 02:04:33PM +0100, Ingo Molnar wrote: > > > > * Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote: > > > > > - spin_lock(&new_base->lock); > > > - spin_lock(&old_base->lock); > > > + /* > > > + * If we take a lock from a different cpu, make sure we have always > > > + * the same locking order. That is the lock that belongs to the cpu > > > + * with the lowest number is taken first. > > > + */ > > > + lock1 = smp_processor_id() < cpu ? &new_base->lock : &old_base->lock; > > > + lock2 = smp_processor_id() < cpu ? &old_base->lock : &new_base->lock; > > > + spin_lock(lock1); > > > + spin_lock(lock2); > > > > looks good to me. Wouldnt this be cleaner via double_lock_timer() - > > similar to how double_rq_lock() works in kernel/sched.c - instead of > > open-coding it? > > Something like the stuff below? Exploits the knowledge that the two > tvec_base_t's are in a per_cpu array. Otherwise I would end up passing > a lot of redundant stuff. But still I think that isn't a good solution > but rather a hack...? > I'd go for the patch above. Yeah, it'd be nicer to pass in the CPU number(s), use that to make the ordering decision. Perhaps (smp_processor_id() - cpu). > --- > Index: linux-2.6/kernel/timer.c > =================================================================== > --- linux-2.6.orig/kernel/timer.c > +++ linux-2.6/kernel/timer.c > @@ -1640,6 +1640,28 @@ static void migrate_timer_list(tvec_base > } > } > > +static void __devinit double_tvec_lock(tvec_base_t *base1, tvec_base_t *base2) > +{ > + if (base1 < base2) { > + spin_lock(&base1->lock); > + spin_lock(&base2->lock); > + } else { > + spin_lock(&base2->lock); > + spin_lock(&base1->lock); > + } > +} > + > +static void __devinit double_tvec_unlock(tvec_base_t *base1, tvec_base_t *base2) > +{ > + if (base1 < base2) { > + spin_unlock(&base1->lock); > + spin_unlock(&base2->lock); > + } else { > + spin_unlock(&base2->lock); > + spin_unlock(&base1->lock); > + } > +} And to undo the locks in the reverse order from that in which they were taken. - To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html