On Tue, 2015-04-07 at 21:17 +0200, Thomas Gleixner wrote:
> On Tue, 7 Apr 2015, Jason Low wrote:
> > The lock shouldn't be used in get_next_timer_interrupt() either right?
> >
> > unsigned long get_next_timer_interrupt(unsigned long now)
> > {
> > ...
> >
> > #ifdef CONFIG_PREEMPT_RT_FULL
> > /*
> > * On PREEMPT_RT we cannot sleep here. If the trylock does not
> > * succeed then we return the worst-case 'expires in 1 tick'
> > * value. We use the rt functions here directly to avoid a
> > * migrate_disable() call.
> > */
> > if (!spin_do_trylock(&base->lock))
> > return now + 1;
> > #else
>
> And how do you protect the walk of the timer wheel against a
> concurrent insertion/removal?
So I just wanted to mention that the issue also applies to
get_next_timer_interrupt(), in addition to run_local_timers(), but if we
really want to remove the lock there, can we always return "now + 1" for
PREEMPT_RT_FULL?
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