tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.19.y head: e864f43593ccf9180c61738abdf1c1dde091367d commit: 742f2319cbd61d9a051f532ad8c83bb33b48f442 [5653/9999] sched/fair: Scale bandwidth quota and period without losing quota/period ratio precision config: parisc-randconfig-r023-20201213 (attached as .config) compiler: hppa-linux-gcc (GCC) 9.3.0 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-4.19.y git checkout 742f2319cbd61d9a051f532ad8c83bb33b48f442 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 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: In function 'sched_cfs_period_timer': 4905 | } | ^ vim +4905 kernel/sched/fair.c c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4853 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4854 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4855 { 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4856 struct cfs_bandwidth *cfs_b = 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4857 container_of(timer, struct cfs_bandwidth, period_timer); 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4858 int overrun; 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4859 int idle = 0; c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4860 int count = 0; 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4861 51f2176d74ace4c kernel/sched/fair.c Ben Segall 2014-05-19 4862 raw_spin_lock(&cfs_b->lock); 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4863 for (;;) { 77a4d1a1b9a122c kernel/sched/fair.c Peter Zijlstra 2015-04-15 4864 overrun = hrtimer_forward_now(timer, cfs_b->period); 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4865 if (!overrun) 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4866 break; 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4867 c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4868 if (++count > 3) { c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4869 u64 new, old = ktime_to_ns(cfs_b->period); c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4870 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4871 /* 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4872 * Grow period by a factor of 2 to avoid losing precision. 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4873 * Precision loss in the quota/period ratio can cause __cfs_schedulable 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4874 * to fail. 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4875 */ 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4876 new = old * 2; 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4877 if (new < max_cfs_quota_period) { c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4878 cfs_b->period = ns_to_ktime(new); 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4879 cfs_b->quota *= 2; c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4880 c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4881 pr_warn_ratelimited( 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4882 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n", c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4883 smp_processor_id(), c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4884 div_u64(new, NSEC_PER_USEC), c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4885 div_u64(cfs_b->quota, NSEC_PER_USEC)); 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4886 } else { 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4887 pr_warn_ratelimited( 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4888 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n", 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4889 smp_processor_id(), 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4890 div_u64(old, NSEC_PER_USEC), 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4891 div_u64(cfs_b->quota, NSEC_PER_USEC)); 742f2319cbd61d9 kernel/sched/fair.c Xuewei Zhang 2019-10-03 4892 } c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4893 c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4894 /* reset count so we don't come right back in here */ c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4895 count = 0; c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4896 } c3edd427d5389ca kernel/sched/fair.c Phil Auld 2019-04-23 4897 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4898 idle = do_sched_cfs_period_timer(cfs_b, overrun); 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4899 } 4cfafd3082afc70 kernel/sched/fair.c Peter Zijlstra 2015-05-14 4900 if (idle) 4cfafd3082afc70 kernel/sched/fair.c Peter Zijlstra 2015-05-14 4901 cfs_b->period_active = 0; 51f2176d74ace4c kernel/sched/fair.c Ben Segall 2014-05-19 4902 raw_spin_unlock(&cfs_b->lock); 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4903 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4904 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 @4905 } 029632fbb7b7c9d kernel/sched_fair.c Peter Zijlstra 2011-10-25 4906 :::::: The code at line 4905 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