On Fri, Apr 21, 2017 at 10:49:29PM -0400, Steven Rostedt wrote: > When a CPU schedules in a lower priority task and wants to make sure > overloaded CPUs know about it. It increments the rto_loop_next. Then it does > an atomic_inc_return() on rto_loop_start. If the returned value is not "1", > then it does atomic_dec() on rt_loop_start and returns. If the value is "1", > then it will take the rto_lock to synchronize with a possible IPI being sent > around to the overloaded CPUs.
> + start = atomic_inc_return(&rq->rd->rto_loop_start); > + if (start != 1) > + goto out; > +out: > + atomic_dec(&rq->rd->rto_loop_start); Did you just write a very expensive test-and-set trylock?
