Re: [PATCH v2] sched/core: add forced idle accounting for cgroups

From: Josh Don <joshdon@google.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: kbuild@lists.01.org, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Tejun Heo <tj@kernel.org>, 0day robot <lkp@intel.com>,
	kbuild-all@lists.01.org,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Cruz Zhao <CruzZhao@linux.alibaba.com>
Subject: Re: [PATCH v2] sched/core: add forced idle accounting for cgroups
Date: Mon, 23 May 2022 14:20:29 -0700	[thread overview]
Message-ID: <CABk29NsNvAs_GFpUEObMWHUw75jp5aBoK3RkPaUL_tDxwxDR=w@mail.gmail.com> (raw)
In-Reply-To: <202205211525.XlF6P8dM-lkp@intel.com>

On Mon, May 23, 2022 at 4:28 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> Hi Josh,
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Josh-Don/sched-core-add-forced-idle-accounting-for-cgroups/20220521-075311
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next
> config: x86_64-randconfig-m001 (https://download.01.org/0day-ci/archive/20220521/202205211525.XlF6P8dM-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-1) 11.3.0
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> smatch warnings:
> kernel/cgroup/rstat.c:489 cgroup_base_stat_cputime_show() error: uninitialized symbol 'forceidle_time'.
>
> vim +/forceidle_time +489 kernel/cgroup/rstat.c
>
> d4ff749b5e0f1e kernel/cgroup/rstat.c Tejun Heo    2018-04-26  460  void cgroup_base_stat_cputime_show(struct seq_file *seq)
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  461  {
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  462       struct cgroup *cgrp = seq_css(seq)->cgroup;
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  463       u64 usage, utime, stime;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  464       struct cgroup_base_stat bstat;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  465       u64 __maybe_unused forceidle_time;
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  466
> 936f2a70f2077f kernel/cgroup/rstat.c Boris Burkov 2020-05-27  467       if (cgroup_parent(cgrp)) {
> 6162cef0f741c7 kernel/cgroup/rstat.c Tejun Heo    2018-04-26  468               cgroup_rstat_flush_hold(cgrp);
> d4ff749b5e0f1e kernel/cgroup/rstat.c Tejun Heo    2018-04-26  469               usage = cgrp->bstat.cputime.sum_exec_runtime;
> 936f2a70f2077f kernel/cgroup/rstat.c Boris Burkov 2020-05-27  470               cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
> 936f2a70f2077f kernel/cgroup/rstat.c Boris Burkov 2020-05-27  471                              &utime, &stime);
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  472  #ifdef CONFIG_SCHED_CORE
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  473               forceidle_time = cgrp->bstat.forceidle_sum;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  474  #endif
> 6162cef0f741c7 kernel/cgroup/rstat.c Tejun Heo    2018-04-26  475               cgroup_rstat_flush_release();
> 936f2a70f2077f kernel/cgroup/rstat.c Boris Burkov 2020-05-27  476       } else {
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  477               root_cgroup_cputime(&bstat);
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  478               usage = bstat.cputime.sum_exec_runtime;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  479               utime = bstat.cputime.utime;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  480               stime = bstat.cputime.stime;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  481  #ifdef CONFIG_SCHED_CORE
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  482               forceidle_time = bstat.forceidle_sum;
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  483  #endif
> 936f2a70f2077f kernel/cgroup/rstat.c Boris Burkov 2020-05-27  484       }
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  485
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  486       do_div(usage, NSEC_PER_USEC);
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  487       do_div(utime, NSEC_PER_USEC);
> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  488       do_div(stime, NSEC_PER_USEC);
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20 @489       do_div(forceidle_time, NSEC_PER_USEC);
>
> I think this will cause MEMSan warnings at run time.

Whoops, I missed wrapping this usage with an #ifdef CONFIG_SCHED_CORE.

> 041cd640b2f3c5 kernel/cgroup/stat.c  Tejun Heo    2017-09-25  490
> d41bf8c9deaed1 kernel/cgroup/stat.c  Tejun Heo    2017-10-23  491       seq_printf(seq, "usage_usec %llu\n"
> d41bf8c9deaed1 kernel/cgroup/stat.c  Tejun Heo    2017-10-23  492                  "user_usec %llu\n"
> d41bf8c9deaed1 kernel/cgroup/stat.c  Tejun Heo    2017-10-23  493                  "system_usec %llu\n",
> d41bf8c9deaed1 kernel/cgroup/stat.c  Tejun Heo    2017-10-23  494                  usage, utime, stime);
> 0575a42c9f10cd kernel/cgroup/rstat.c Josh Don     2022-05-20  495
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
>