From: Peter Zijlstra <peterz@infradead.org>
To: Chengming Zhou <zhouchengming@bytedance.com>
Cc: tj@kernel.org, arbn@yandex-team.com, mingo@redhat.com,
linux-kernel@vger.kernel.org, Minye Zhu <zhuminye@bytedance.com>
Subject: Re: [PATCH] sched/cpuacct: fix charge percpu cpuusage
Date: Mon, 14 Feb 2022 11:09:01 +0100 [thread overview]
Message-ID: <YgoqPT67g2NcV/eH@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220213120118.93471-1-zhouchengming@bytedance.com>
On Sun, Feb 13, 2022 at 08:01:18PM +0800, Chengming Zhou wrote:
> 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.
>
> Reported-by: Minye Zhu <zhuminye@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Can I get a Fixes: tag for this?
> ---
> 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..75fbc212cb71 100644
> --- a/kernel/sched/cpuacct.c
> +++ b/kernel/sched/cpuacct.c
> @@ -335,11 +335,12 @@ static struct cftype files[] = {
> void cpuacct_charge(struct task_struct *tsk, u64 cputime)
> {
> struct cpuacct *ca;
> + unsigned int cpu = task_cpu(tsk);
>
> 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();
> }
Also, while we there, what about this as an additional patch?
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -334,15 +334,13 @@ static struct cftype files[] = {
*/
void cpuacct_charge(struct task_struct *tsk, u64 cputime)
{
- struct cpuacct *ca;
unsigned int cpu = task_cpu(tsk);
+ struct cpuacct *ca;
- rcu_read_lock();
+ lockdep_assert_rq_held(cpu_rq(cpu));
for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
*per_cpu_ptr(ca->cpuusage, cpu) += cputime;
-
- rcu_read_unlock();
}
/*
next prev parent reply other threads:[~2022-02-14 10:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-13 12:01 [PATCH] sched/cpuacct: fix charge percpu cpuusage Chengming Zhou
2022-02-14 10:09 ` Peter Zijlstra [this message]
2022-02-14 18:57 ` Tejun Heo
2022-02-15 12:23 ` [Phishing Risk] [External] " Chengming Zhou
2022-02-15 12:19 ` Chengming Zhou
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