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);
?
Regards,
Boqun
> + if (is_idle_task(rq->curr))
> + resched_curr(rq);
> + }
> }
>
> bool cpus_share_cache(int this_cpu, int that_cpu)
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1678,6 +1678,21 @@ rq_unlock(struct rq *rq, struct rq_flags
> raw_spin_rq_unlock(rq);
> }
>
> +DEFINE_LOCK_GUARD_1(rq_lock, struct rq,
> + rq_lock(_T->lock, &_T->rf),
> + rq_unlock(_T->lock, &_T->rf),
> + struct rq_flags rf)
> +
> +DEFINE_LOCK_GUARD_1(rq_lock_irq, struct rq,
> + rq_lock_irq(_T->lock, &_T->rf),
> + rq_unlock_irq(_T->lock, &_T->rf),
> + struct rq_flags rf)
> +
> +DEFINE_LOCK_GUARD_1(rq_lock_irqsave, struct rq,
> + rq_lock_irqsave(_T->lock, &_T->rf),
> + rq_unlock_irqrestore(_T->lock, &_T->rf),
> + struct rq_flags rf)
> +
> static inline struct rq *
> this_rq_lock_irq(struct rq_flags *rf)
> __acquires(rq->lock)
>
>
