linux-kernel - [PATCH] sched: Filter root_task

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Message-Id: <20230922094336.394865-1-haifeng.xu@shopee.com>
Date:   Fri, 22 Sep 2023 09:43:36 +0000
From:   Haifeng Xu <haifeng.xu@...pee.com>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, vincent.guittot@...aro.org,
        juri.lelli@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org, Haifeng Xu <haifeng.xu@...pee.com>
Subject: [PATCH] sched: Filter root_task_group at the beginning

We can't change the weight of the root cgroup. Let's handle
root_task_group before doing any real work including acquiring
the shares_mutex.

Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
---
 kernel/sched/fair.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a80a73909dc2..1ac2df87e070 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12594,6 +12594,9 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
 {
 	int ret;
 
+	if (tg == &root_task_group)
+		return -EINVAL;
+
 	mutex_lock(&shares_mutex);
 	if (tg_is_idle(tg))
 		ret = -EINVAL;
-- 
2.25.1