Hi Xuewei, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.9.y head: 6940a98776c9014fdcc806e39ab0ebc8316cf241 commit: bdb6fa8234e59dfb1e0136352adf7684ac9c11af [8018/9999] sched/fair: Scale bandwidth quota and period without losing quota/period ratio precision config: parisc-allyesconfig (attached as .config) compiler: hppa-linux-gcc (GCC) 7.5.0 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/stable/linux-stable-rc.gi... git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git git fetch --no-tags linux-stable-rc linux-4.9.y git checkout bdb6fa8234e59dfb1e0136352adf7684ac9c11af # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-7.5.0 make.cross ARCH=parisc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/sched/fair.c:3233:6: warning: no previous prototype for 'remove_entity_load_avg' [-Wmissing-prototypes] void remove_entity_load_avg(struct sched_entity *se) ^~~~~~~~~~~~~~~~~~~~~~ kernel/sched/fair.c: In function 'sched_cfs_period_timer': } ^ vim +4428 kernel/sched/fair.c 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4376 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4377 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4378 { 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4379 struct cfs_bandwidth *cfs_b = 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4380 container_of(timer, struct cfs_bandwidth, period_timer); 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4381 int overrun; 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4382 int idle = 0; 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4383 int count = 0; 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4384 51f2176d74ace4 kernel/sched/fair.c Ben Segall 2014-05-19 4385 raw_spin_lock(&cfs_b->lock); 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4386 for (;;) { 77a4d1a1b9a122 kernel/sched/fair.c Peter Zijlstra 2015-04-15 4387 overrun = hrtimer_forward_now(timer, cfs_b->period); 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4388 if (!overrun) 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4389 break; 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4390 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4391 if (++count > 3) { 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4392 u64 new, old = ktime_to_ns(cfs_b->period); 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4393 bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4394 /* bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4395 * Grow period by a factor of 2 to avoid losing precision. bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4396 * Precision loss in the quota/period ratio can cause __cfs_schedulable bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4397 * to fail. bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4398 */ bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4399 new = old * 2; bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4400 if (new < max_cfs_quota_period) { 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4401 cfs_b->period = ns_to_ktime(new); bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4402 cfs_b->quota *= 2; 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4403 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4404 pr_warn_ratelimited( bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4405 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n", 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4406 smp_processor_id(), 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4407 div_u64(new, NSEC_PER_USEC), 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4408 div_u64(cfs_b->quota, NSEC_PER_USEC)); bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4409 } else { bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4410 pr_warn_ratelimited( bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4411 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n", bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4412 smp_processor_id(), bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4413 div_u64(old, NSEC_PER_USEC), bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4414 div_u64(cfs_b->quota, NSEC_PER_USEC)); bdb6fa8234e59d kernel/sched/fair.c Xuewei Zhang 2019-10-03 4415 } 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4416 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4417 /* reset count so we don't come right back in here */ 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4418 count = 0; 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4419 } 33f2a3e176bd50 kernel/sched/fair.c Phil Auld 2019-04-23 4420 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4421 idle = do_sched_cfs_period_timer(cfs_b, overrun); 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4422 } 4cfafd3082afc7 kernel/sched/fair.c Peter Zijlstra 2015-05-14 4423 if (idle) 4cfafd3082afc7 kernel/sched/fair.c Peter Zijlstra 2015-05-14 4424 cfs_b->period_active = 0; 51f2176d74ace4 kernel/sched/fair.c Ben Segall 2014-05-19 4425 raw_spin_unlock(&cfs_b->lock); 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4426 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4427 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 @4428 } 029632fbb7b7c9 kernel/sched_fair.c Peter Zijlstra 2011-10-25 4429 :::::: The code at line 4428 was first introduced by commit :::::: 029632fbb7b7c9d85063cc9eb470de6c54873df3 sched: Make separate sched*.c translation units :::::: TO: Peter Zijlstra <a.p.zijlstra(a)chello.nl&gt; :::::: CC: Ingo Molnar <mingo(a)elte.hu&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org