On Thu, Oct 15, 2020 at 12:12:35PM +0200, Peter Zijlstra wrote: > On Thu, Oct 15, 2020 at 01:40:53AM +0200, Frederic Weisbecker wrote: > > > re tick_nohz_task_switch() being placed wrong, it should probably be > > > placed before finish_lock_switch(). Something like so. > > > > > > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > > index cf044580683c..5c92c959824f 100644 > > > --- a/kernel/sched/core.c > > > +++ b/kernel/sched/core.c > > > @@ -4084,6 +4084,7 @@ static struct rq *finish_task_switch(struct > > > task_struct *prev) > > > vtime_task_switch(prev); > > > perf_event_task_sched_in(prev, current); > > > finish_task(prev); > > > + tick_nohz_task_switch(); > > > finish_lock_switch(rq); > > > finish_arch_post_lock_switch(); > > > kcov_finish_switch(current); > > > @@ -4121,7 +4122,6 @@ static struct rq *finish_task_switch(struct > > > task_struct *prev) > > > put_task_struct_rcu_user(prev); > > > } > > > > > > - tick_nohz_task_switch(); > > > > IIRC, we wanted to keep it outside rq lock because it shouldn't it... > > But now you've created a window with IRQs on and cause additional IRQ > state changes. > > If you're really worried about rq->lock, I suppose we can do: > > rq_unlock(rq->lock); > tick_nohz_task_switch(); > local_irq_enable(); > > (much like we do at the beginning of __schedule for RCU)
Right. Well I'm not that worried about rq->lock though. If you're ok with it I can just move it before finish_lock_switch(). Thanks.
