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Date: Sat, 11 Sep 2021 09:46:21 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: kernel test robot <lkp@...el.com>
Cc: kbuild-all@...ts.01.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [peterz-queue:sched/core 13/19] kernel/sched/fair.c:892:34:
warning: variable 'stats' set but not used
On Sat, Sep 11, 2021 at 2:21 AM kernel test robot <lkp@...el.com> wrote:
>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core
> head: 2dfdb3d20ad50e2ae2cb84cbceb0f0fc75e79e5d
> commit: 445d9e8ba05d5e9e4b26956b7fe529223e29d8d1 [13/19] sched: make struct sched_statistics independent of fair sched class
> config: m68k-buildonly-randconfig-r002-20210910 (attached as .config)
> compiler: m68k-linux-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=445d9e8ba05d5e9e4b26956b7fe529223e29d8d1
> git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git
> git fetch --no-tags peterz-queue sched/core
> git checkout 445d9e8ba05d5e9e4b26956b7fe529223e29d8d1
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=m68k
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> kernel/sched/fair.c: In function 'update_curr':
> kernel/sched/fair.c:860:42: warning: unused variable 'stats' [-Wunused-variable]
> 860 | struct sched_statistics *stats = __schedstats_from_se(curr);
> | ^~~~~
> kernel/sched/fair.c: In function 'update_stats_wait_start':
> >> kernel/sched/fair.c:892:34: warning: variable 'stats' set but not used [-Wunused-but-set-variable]
> 892 | struct sched_statistics *stats;
> | ^~~~~
> kernel/sched/fair.c: In function 'update_stats_wait_end':
> kernel/sched/fair.c:912:34: warning: variable 'stats' set but not used [-Wunused-but-set-variable]
> 912 | struct sched_statistics *stats;
> | ^~~~~
> kernel/sched/fair.c: In function 'update_stats_enqueue_sleeper':
> kernel/sched/fair.c:956:34: warning: variable 'stats' set but not used [-Wunused-but-set-variable]
> 956 | struct sched_statistics *stats;
> | ^~~~~
> kernel/sched/fair.c: In function 'set_next_entity':
> kernel/sched/fair.c:4517:42: warning: unused variable 'stats' [-Wunused-variable]
> 4517 | struct sched_statistics *stats = __schedstats_from_se(se);
> | ^~~~~
> kernel/sched/fair.c: At top level:
> kernel/sched/fair.c:5505:6: warning: no previous prototype for 'init_cfs_bandwidth' [-Wmissing-prototypes]
> 5505 | void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
> | ^~~~~~~~~~~~~~~~~~
> kernel/sched/fair.c:11661:6: warning: no previous prototype for 'free_fair_sched_group' [-Wmissing-prototypes]
> 11661 | void free_fair_sched_group(struct task_group *tg) { }
> | ^~~~~~~~~~~~~~~~~~~~~
> kernel/sched/fair.c:11663:5: warning: no previous prototype for 'alloc_fair_sched_group' [-Wmissing-prototypes]
> 11663 | int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
> | ^~~~~~~~~~~~~~~~~~~~~~
> kernel/sched/fair.c:11668:6: warning: no previous prototype for 'online_fair_sched_group' [-Wmissing-prototypes]
> 11668 | void online_fair_sched_group(struct task_group *tg) { }
> | ^~~~~~~~~~~~~~~~~~~~~~~
> kernel/sched/fair.c:11670:6: warning: no previous prototype for 'unregister_fair_sched_group' [-Wmissing-prototypes]
> 11670 | void unregister_fair_sched_group(struct task_group *tg) { }
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> vim +/stats +892 kernel/sched/fair.c
>
> 840
> 841 /*
> 842 * Update the current task's runtime statistics.
> 843 */
> 844 static void update_curr(struct cfs_rq *cfs_rq)
> 845 {
> 846 struct sched_entity *curr = cfs_rq->curr;
> 847 u64 now = rq_clock_task(rq_of(cfs_rq));
> 848 u64 delta_exec;
> 849
> 850 if (unlikely(!curr))
> 851 return;
> 852
> 853 delta_exec = now - curr->exec_start;
> 854 if (unlikely((s64)delta_exec <= 0))
> 855 return;
> 856
> 857 curr->exec_start = now;
> 858
> 859 if (schedstat_enabled()) {
> > 860 struct sched_statistics *stats = __schedstats_from_se(curr);
> 861
> 862 __schedstat_set(stats->exec_max,
> 863 max(delta_exec, stats->exec_max));
> 864 }
> 865
> 866 curr->sum_exec_runtime += delta_exec;
> 867 schedstat_add(cfs_rq->exec_clock, delta_exec);
> 868
> 869 curr->vruntime += calc_delta_fair(delta_exec, curr);
> 870 update_min_vruntime(cfs_rq);
> 871
> 872 if (entity_is_task(curr)) {
> 873 struct task_struct *curtask = task_of(curr);
> 874
> 875 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
> 876 cgroup_account_cputime(curtask, delta_exec);
> 877 account_group_exec_runtime(curtask, delta_exec);
> 878 }
> 879
> 880 account_cfs_rq_runtime(cfs_rq, delta_exec);
> 881 }
> 882
> 883 static void update_curr_fair(struct rq *rq)
> 884 {
> 885 update_curr(cfs_rq_of(&rq->curr->se));
> 886 }
> 887
> 888 static inline void
> 889 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
> 890 {
> 891 u64 wait_start, prev_wait_start;
> > 892 struct sched_statistics *stats;
> 893
> 894 if (!schedstat_enabled())
> 895 return;
> 896
> 897 stats = __schedstats_from_se(se);
> 898
> 899 wait_start = rq_clock(rq_of(cfs_rq));
> 900 prev_wait_start = schedstat_val(stats->wait_start);
> 901
> 902 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
> 903 likely(wait_start > prev_wait_start))
> 904 wait_start -= prev_wait_start;
> 905
> 906 __schedstat_set(stats->wait_start, wait_start);
> 907 }
> 908
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Thanks for the report.
This build warning happens when CONFIG_SCHEDSTATS is not set, in which
case the schedstat_* functions will be none.
Should add '__maybe_unused' to fix it.
I will send a fix.
--
Thanks
Yafang
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