sched/fair: Fixup wake_up_sync() vs DELAYED_DEQUEUE

Delayed dequeued feature keeps a sleeping task enqueued until its
lag has elapsed. As a result, it stays also visible in rq->nr_running.
So when in wake_affine_idle(), we should use the real running-tasks
in rq to check whether we should place the wake-up task to
current cpu.
On the other hand, add a helper function to return the nr-delayed.

Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Reviewed-and-tested-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20250303105241.17251-2-xuewen.yan@unisoc.com

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index eb5a2572b4f8b6b5517befc299312b6ae7476e88..b00f16700f9c5b46f04e01c822a857dd8b520197 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7193,6 +7193,11 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
        return true;
 }
 
+static inline unsigned int cfs_h_nr_delayed(struct rq *rq)
+{
+       return (rq->cfs.h_nr_queued - rq->cfs.h_nr_runnable);
+}
+
 #ifdef CONFIG_SMP
 
 /* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
@@ -7354,8 +7359,12 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
        if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
                return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
 
-       if (sync && cpu_rq(this_cpu)->nr_running == 1)
-               return this_cpu;
+       if (sync) {
+               struct rq *rq = cpu_rq(this_cpu);
+
+               if ((rq->nr_running - cfs_h_nr_delayed(rq)) == 1)
+                       return this_cpu;
+       }
 
        if (available_idle_cpu(prev_cpu))
                return prev_cpu;