linux-kernel - [PATCH v2] sched/fair: Fix cfs_rq_is

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Date:   Wed, 13 Sep 2023 13:20:31 +0000
From:   chengming.zhou@...ux.dev
To:     mingo@...hat.com, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, chengming.zhou@...ux.dev,
        Chengming Zhou <zhouchengming@...edance.com>,
        Leo Yu-Chi Liang <ycliang@...estech.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH v2] sched/fair: Fix cfs_rq_is_decayed() on !SMP

From: Chengming Zhou <zhouchengming@...edance.com>

We don't need to maintain per-queue leaf_cfs_rq_list on !SMP, since
it's used for cfs_rq load tracking & balance on SMP.

But sched debug interface use it to print per-cfs_rq stats, which
maybe better to change to use walk_tg_tree_from() instead.

This patch just fix the !SMP version cfs_rq_is_decayed(), so the
per-queue leaf_cfs_rq_list is also maintained correctly on !SMP,
to fix the warning in assert_list_leaf_cfs_rq().

Fixes: 0a00a354644e ("sched/fair: Delete useless condition in tg_unthrottle_up()")
Reported-by: Leo Yu-Chi Liang <ycliang@...estech.com>
Closes: https://lore.kernel.org/all/ZN87UsqkWcFLDxea@swlinux02/
Tested-by: Leo Yu-Chi Liang <ycliang@...estech.com>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8dbff6e7ad4f..845d7729320e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4878,7 +4878,7 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
 
 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 {
-	return true;
+	return !(cfs_rq->nr_running);
 }
 
 #define UPDATE_TG	0x0
-- 
2.40.1