On Mon, Jun 12, 2023 at 11:02:28AM -0700, Boqun Feng wrote:
> On Mon, Jun 12, 2023 at 11:07:21AM +0200, Peter Zijlstra wrote:
> > Use guards to reduce gotos and simplify control flow.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > ---
> > kernel/sched/core.c | 20 ++++++--------------
> > kernel/sched/sched.h | 15 +++++++++++++++
> > 2 files changed, 21 insertions(+), 14 deletions(-)
> >
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct
> > void wake_up_if_idle(int cpu)
> > {
> > struct rq *rq = cpu_rq(cpu);
> > - struct rq_flags rf;
> >
> > - rcu_read_lock();
> > -
> > - if (!is_idle_task(rcu_dereference(rq->curr)))
> > - goto out;
> > -
> > - rq_lock_irqsave(rq, &rf);
> > - if (is_idle_task(rq->curr))
> > - resched_curr(rq);
> > - /* Else CPU is not idle, do nothing here: */
> > - rq_unlock_irqrestore(rq, &rf);
> > -
> > -out:
> > - rcu_read_unlock();
> > + guard(rcu)();
> > + if (is_idle_task(rcu_dereference(rq->curr))) {
> > + guard(rq_lock)(rq);
>
> We assume that irq must be disabled when this function called?
> Otherwise, I don't understand why this is not
>
> guard(rq_lock_irqsave)(rq);
>
You're quite right, I messed that up.
