linux-kernel - Re: [PATCH v4 1/2] cgroup/rstat: Fix forceidle time in cpu.stat

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Message-ID: <15581a04-867f-4fc2-ab01-f4bd23e3c035@bytedance.com>
Date: Thu, 27 Feb 2025 18:37:45 +0800
From: Abel Wu <wuyun.abel@...edance.com>
To: Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>,
 Michal Koutný <mkoutny@...e.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 Bitao Hu <yaoma@...ux.alibaba.com>, Thomas Gleixner <tglx@...utronix.de>,
 Andrew Morton <akpm@...ux-foundation.org>, Yury Norov
 <yury.norov@...il.com>, Chen Ridong <chenridong@...wei.com>
Cc: "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] cgroup/rstat: Fix forceidle time in cpu.stat

Hi Tejun, can you please pick this fix? Since there is no objections..

Thanks!

On 2/9/25 2:13 PM, Abel Wu wrote:
> The commit b824766504e4 ("cgroup/rstat: add force idle show helper")
> retrieves forceidle_time outside cgroup_rstat_lock for non-root cgroups
> which can be potentially inconsistent with other stats.
> 
> Rather than reverting that commit, fix it in a way that retains the
> effort of cleaning up the ifdef-messes.
> 
> Fixes: b824766504e4 ("cgroup/rstat: add force idle show helper")
> Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
> ---
>   kernel/cgroup/rstat.c | 29 +++++++++++++----------------
>   1 file changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> index 5877974ece92..c2784c317cdd 100644
> --- a/kernel/cgroup/rstat.c
> +++ b/kernel/cgroup/rstat.c
> @@ -613,36 +613,33 @@ static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat
>   void cgroup_base_stat_cputime_show(struct seq_file *seq)
>   {
>   	struct cgroup *cgrp = seq_css(seq)->cgroup;
> -	u64 usage, utime, stime, ntime;
> +	struct cgroup_base_stat bstat;
>   
>   	if (cgroup_parent(cgrp)) {
>   		cgroup_rstat_flush_hold(cgrp);
> -		usage = cgrp->bstat.cputime.sum_exec_runtime;
> +		bstat = cgrp->bstat;
>   		cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
> -			       &utime, &stime);
> -		ntime = cgrp->bstat.ntime;
> +			       &bstat.cputime.utime, &bstat.cputime.stime);
>   		cgroup_rstat_flush_release(cgrp);
>   	} else {
> -		/* cgrp->bstat of root is not actually used, reuse it */
> -		root_cgroup_cputime(&cgrp->bstat);
> -		usage = cgrp->bstat.cputime.sum_exec_runtime;
> -		utime = cgrp->bstat.cputime.utime;
> -		stime = cgrp->bstat.cputime.stime;
> -		ntime = cgrp->bstat.ntime;
> +		root_cgroup_cputime(&bstat);
>   	}
>   
> -	do_div(usage, NSEC_PER_USEC);
> -	do_div(utime, NSEC_PER_USEC);
> -	do_div(stime, NSEC_PER_USEC);
> -	do_div(ntime, NSEC_PER_USEC);
> +	do_div(bstat.cputime.sum_exec_runtime, NSEC_PER_USEC);
> +	do_div(bstat.cputime.utime, NSEC_PER_USEC);
> +	do_div(bstat.cputime.stime, NSEC_PER_USEC);
> +	do_div(bstat.ntime, NSEC_PER_USEC);
>   
>   	seq_printf(seq, "usage_usec %llu\n"
>   			"user_usec %llu\n"
>   			"system_usec %llu\n"
>   			"nice_usec %llu\n",
> -			usage, utime, stime, ntime);
> +			bstat.cputime.sum_exec_runtime,
> +			bstat.cputime.utime,
> +			bstat.cputime.stime,
> +			bstat.ntime);
>   
> -	cgroup_force_idle_show(seq, &cgrp->bstat);
> +	cgroup_force_idle_show(seq, &bstat);
>   }
>   
>   /* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */