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sched: Simplify yield_to()

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Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2023-06-09 16:58:23 +02:00 committed by Ingo Molnar
parent 92c2ec5bc1
commit 7a50f76674
1 changed files with 32 additions and 41 deletions
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73
kernel/sched/core.c
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@ -8888,55 +8888,46 @@ int __sched yield_to(struct task_struct *p, bool preempt)
{
struct task_struct *curr = current;
struct rq *rq, *p_rq;
unsigned long flags;
int yielded = 0;
local_irq_save(flags);
rq = this_rq();
scoped_guard (irqsave) {
rq = this_rq();
again:
p_rq = task_rq(p);
/*
* If we're the only runnable task on the rq and target rq also
* has only one task, there's absolutely no point in yielding.
*/
if (rq->nr_running == 1 && p_rq->nr_running == 1) {
yielded = -ESRCH;
goto out_irq;
}
double_rq_lock(rq, p_rq);
if (task_rq(p) != p_rq) {
double_rq_unlock(rq, p_rq);
goto again;
}
if (!curr->sched_class->yield_to_task)
goto out_unlock;
if (curr->sched_class != p->sched_class)
goto out_unlock;
if (task_on_cpu(p_rq, p) || !task_is_running(p))
goto out_unlock;
yielded = curr->sched_class->yield_to_task(rq, p);
if (yielded) {
schedstat_inc(rq->yld_count);
p_rq = task_rq(p);
/*
* Make p's CPU reschedule; pick_next_entity takes care of
* fairness.
* If we're the only runnable task on the rq and target rq also
* has only one task, there's absolutely no point in yielding.
*/
if (preempt && rq != p_rq)
resched_curr(p_rq);
if (rq->nr_running == 1 && p_rq->nr_running == 1)
return -ESRCH;
guard(double_rq_lock)(rq, p_rq);
if (task_rq(p) != p_rq)
goto again;
if (!curr->sched_class->yield_to_task)
return 0;
if (curr->sched_class != p->sched_class)
return 0;
if (task_on_cpu(p_rq, p) || !task_is_running(p))
return 0;
yielded = curr->sched_class->yield_to_task(rq, p);
if (yielded) {
schedstat_inc(rq->yld_count);
/*
* Make p's CPU reschedule; pick_next_entity
* takes care of fairness.
*/
if (preempt && rq != p_rq)
resched_curr(p_rq);
}
}
out_unlock:
double_rq_unlock(rq, p_rq);
out_irq:
local_irq_restore(flags);
if (yielded > 0)
if (yielded)
schedule();
return yielded;