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Thu, 23 Jan 2025 23:49:25 -0800 (PST) Received: from [10.254.144.106] ([139.177.225.251]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72f8a69f5fdsm1208111b3a.5.2025.01.23.23.49.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jan 2025 23:49:25 -0800 (PST) Message-ID: <2bba87cf-69aa-4fac-ae1a-c50e2f376e2a@bytedance.com> Date: Fri, 24 Jan 2025 15:49:16 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Re: [PATCH 1/3] cgroup/rstat: Fix forceidle time in cpu.stat Content-Language: en-US To: chenridong , Tejun Heo , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Jonathan Corbet , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Thomas Gleixner , Yury Norov , Andrew Morton , Bitao Hu Cc: "open list:CONTROL GROUP (CGROUP)" , "open list:DOCUMENTATION" , open list References: <20250123174713.25570-1-wuyun.abel@bytedance.com> <20250123174713.25570-2-wuyun.abel@bytedance.com> <853d2669-e05b-435e-9ac1-86311ead56e5@huawei.com> From: Abel Wu In-Reply-To: <853d2669-e05b-435e-9ac1-86311ead56e5@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/24/25 9:47 AM, chenridong Wrote: > > > On 2025/1/24 1:47, 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 >> --- >> 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; > > 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/ Thanks for pointing out. Using memcpy() is fine for me, but I see cgroup_base_stat_flush() is using the same pattern, and if we don't want copy like this, it would be better unify them in a separate patch. But IMHO in either way, I don't think reading forceidle time outside cgroup_rstat_lock is the right thing to do. Best Regards, Abel