linux-kernel - [PATCH v3 1/3] sched/cpuacct: fix charge percpu cpuusage

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Message-Id: <20220220051426.5274-1-zhouchengming@bytedance.com>
Date:   Sun, 20 Feb 2022 13:14:24 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        bristot@...hat.com, zhaolei@...fujitsu.com, tj@...nel.org,
        lizefan.x@...edance.com, hannes@...xchg.org
Cc:     linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>,
        Minye Zhu <zhuminye@...edance.com>
Subject: [PATCH v3 1/3] sched/cpuacct: fix charge percpu cpuusage

The cpuacct_account_field() is always called by the current task
itself, so it's ok to use __this_cpu_add() to charge the tick time.

But cpuacct_charge() maybe called by update_curr() in load_balance()
on a random CPU, different from the CPU on which the task is running.
So __this_cpu_add() will charge that cputime to a random incorrect CPU.

Fixes: 73e6aafd9ea8 ("sched/cpuacct: Simplify the cpuacct code")
Reported-by: Minye Zhu <zhuminye@...edance.com>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 kernel/sched/cpuacct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 3d06c5e4220d..307800586ac8 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -334,12 +334,13 @@ static struct cftype files[] = {
  */
 void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 {
+	unsigned int cpu = task_cpu(tsk);
 	struct cpuacct *ca;
 
 	rcu_read_lock();
 
 	for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
-		__this_cpu_add(*ca->cpuusage, cputime);
+		*per_cpu_ptr(ca->cpuusage, cpu) += cputime;
 
 	rcu_read_unlock();
 }
-- 
2.20.1