linux-kernel - [tip: sched/urgent] sched/fair: Fix clearing of has_idle_cores flag in select_idle

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Message-ID: <162080926950.29796.5635598249768970052.tip-bot2@tip-bot2>
Date:   Wed, 12 May 2021 08:47:49 -0000
From:   "tip-bot2 for Gautham R. Shenoy" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Mel Gorman <mgorman@...hsingularity.net>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/urgent] sched/fair: Fix clearing of has_idle_cores flag
 in select_idle_cpu()

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     02dbb7246c5bbbbe1607ebdc546ba5c454a664b1
Gitweb:        https://git.kernel.org/tip/02dbb7246c5bbbbe1607ebdc546ba5c454a664b1
Author:        Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
AuthorDate:    Tue, 11 May 2021 20:46:09 +05:30
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 12 May 2021 10:41:28 +02:00

sched/fair: Fix clearing of has_idle_cores flag in select_idle_cpu()

In commit:

  9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")

in select_idle_cpu(), we check if an idle core is present in the LLC
of the target CPU via the flag "has_idle_cores". We look for the idle
core in select_idle_cores(). If select_idle_cores() isn't able to find
an idle core/CPU, we need to unset the has_idle_cores flag in the LLC
of the target to prevent other CPUs from going down this route.

However, the current code is unsetting it in the LLC of the current
CPU instead of the target CPU. This patch fixes this issue.

Fixes: 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@...hsingularity.net>
Link: https://lore.kernel.org/r/1620746169-13996-1-git-send-email-ego@linux.vnet.ibm.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 20aa234..3248e24 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6217,7 +6217,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool 
 	}
 
 	if (has_idle_core)
-		set_idle_cores(this, false);
+		set_idle_cores(target, false);
 
 	if (sched_feat(SIS_PROP) && !has_idle_core) {
 		time = cpu_clock(this) - time;