linux-kernel - [PATCH 5.15 561/917] cgroup: Fix rootcg cpu.stat guest double counting

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Message-Id: <20211115165447.820448441@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 18:00:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Schatzberg <schatzberg.dan@...il.com>,
        Tejun Heo <tj@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 561/917] cgroup: Fix rootcg cpu.stat guest double counting

From: Dan Schatzberg <schatzberg.dan@...il.com>

[ Upstream commit 81c49d39aea8a10e6d05d3aa1cb65ceb721e19b0 ]

In account_guest_time in kernel/sched/cputime.c guest time is
attributed to both CPUTIME_NICE and CPUTIME_USER in addition to
CPUTIME_GUEST_NICE and CPUTIME_GUEST respectively. Therefore, adding
both to calculate usage results in double counting any guest time at
the rootcg.

Fixes: 936f2a70f207 ("cgroup: add cpu.stat file to root cgroup")
Signed-off-by: Dan Schatzberg <schatzberg.dan@...il.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/cgroup/rstat.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index b264ab5652ba9..1486768f23185 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -433,8 +433,6 @@ static void root_cgroup_cputime(struct task_cputime *cputime)
 		cputime->sum_exec_runtime += user;
 		cputime->sum_exec_runtime += sys;
 		cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
-		cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST];
-		cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST_NICE];
 	}
 }
 
-- 
2.33.0