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Date: Fri, 24 Jan 2025 13:49:09 -1000
From: Tejun Heo <tj@kernel.org>
To: Abel Wu <wuyun.abel@bytedance.com>
Cc: chenridong <chenridong@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
	Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Yury Norov <yury.norov@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Bitao Hu <yaoma@linux.alibaba.com>,
	"open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: Re: [PATCH 1/3] cgroup/rstat: Fix forceidle time in cpu.stat
Message-ID: <Z5Qm9aXwZhwjBEfy@slm.duckdns.org>
References: <20250123174713.25570-1-wuyun.abel@bytedance.com>
 <20250123174713.25570-2-wuyun.abel@bytedance.com>
 <853d2669-e05b-435e-9ac1-86311ead56e5@huawei.com>
 <2bba87cf-69aa-4fac-ae1a-c50e2f376e2a@bytedance.com>
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In-Reply-To: <2bba87cf-69aa-4fac-ae1a-c50e2f376e2a@bytedance.com>

On Fri, Jan 24, 2025 at 03:49:16PM +0800, Abel Wu wrote:
...
> > > --- 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;
> > 
> > Thank you for finding that.
> > In my version 2, I used to assign cgrp->bstat to bstat.
> > This is Tj's comment:
> > https://lore.kernel.org/linux-kernel/ZoQ2ti7nnz9EJSc3@slm.duckdns.org/

I wasn't saying that memcpy() should be used instead of assignment. I was
saying that if a non-trivial struct can be pointed to instead of being
copied, it should be pointed to. If all the fields need to be snapshotted,
assigning is fine.

Thanks.

-- 
tejun