linux-kernel - [PATCH] sched/fair: Fix misuse of available_idle

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Message-Id: <20220908080702.58938-1-wuyun.abel@bytedance.com>
Date:   Thu,  8 Sep 2022 16:07:02 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Rohit Jain <rohit.k.jain@...cle.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Abel Wu <wuyun.abel@...edance.com>
Subject: [PATCH] sched/fair: Fix misuse of available_idle_cpu()

The function available_idle_cpu() was introduced to distinguish
between the code paths that cares if the vCPU is preempted and
the ones don't care. In general, available_idle_cpu() is used in
selecting cpus for immediate use, e.g. ttwu. While idle_cpu() is
used in the paths that only cares about the cpu is idle or not,
and __update_idle_core() is one of them.

Use idle_cpu() instead in the idle path to make has_idle_core
a better hint.

Fixes: 943d355d7fee (sched/core: Distinguish between idle_cpu() calls based on desired effect, introduce available_idle_cpu())
Signed-off-by: Abel Wu <wuyun.abel@...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 efceb670e755..5a76d814f8bc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6302,7 +6302,7 @@ void __update_idle_core(struct rq *rq)
 		if (cpu == core)
 			continue;
 
-		if (!available_idle_cpu(cpu))
+		if (!idle_cpu(cpu))
 			goto unlock;
 	}
 
-- 
2.37.3