tree: https://github.com/intel/linux-intel-lts.git 4.19/preempt-rt head: 5869b5f01603be1b382db99b966071ac9d840daf commit: cc00a48f20c9ce3f9ae449e55dfdf9fb976ecee1 [5/10] Merge tag 'lts-v4.19.195-base-210628T072840Z' into lts2019/yocto-rt config: ia64-allmodconfig (attached as .config) compiler: ia64-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://github.com/intel/linux-intel-lts/commit/cc00a48f20c9ce3f9ae449e55... git remote add intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-lts 4.19/preempt-rt git checkout cc00a48f20c9ce3f9ae449e55dfdf9fb976ecee1 # save the attached .config to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=ia64 SHELL=/bin/bash kernel/sched/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Note: the intel-lts/4.19/preempt-rt HEAD 5869b5f01603be1b382db99b966071ac9d840daf builds fine. It only hurts bisectability. All errors (new ones prefixed by >>): kernel/sched/fair.c:3656:6: warning: no previous prototype for 'sync_entity_load_avg' [-Wmissing-prototypes] 3656 | void sync_entity_load_avg(struct sched_entity *se) | ^~~~~~~~~~~~~~~~~~~~ kernel/sched/fair.c:3669:6: warning: no previous prototype for 'remove_entity_load_avg' [-Wmissing-prototypes] 3669 | void remove_entity_load_avg(struct sched_entity *se) | ^~~~~~~~~~~~~~~~~~~~~~ kernel/sched/fair.c: In function 'select_idle_cpu': 6190 | cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); | ^~~~~~~~~~~~ | nr_cpus_allowed kernel/sched/fair.c: In function 'update_blocked_averages': kernel/sched/fair.c:7499:14: warning: variable 'done' set but not used [-Wunused-but-set-variable] 7499 | bool done = true; | ^~~~ Kconfig warnings: (for reference only) WARNING: unmet direct dependencies detected for FRAME_POINTER Depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS Selected by - FAULT_INJECTION_STACKTRACE_FILTER && FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT && !X86_64 && !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 vim +6190 kernel/sched/fair.c 10e2f1acd0106c Peter Zijlstra 2016-05-09 6151 10e2f1acd0106c Peter Zijlstra 2016-05-09 6152 /* 10e2f1acd0106c Peter Zijlstra 2016-05-09 6153 * Scan the LLC domain for idle CPUs; this is dynamically regulated by 10e2f1acd0106c Peter Zijlstra 2016-05-09 6154 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the 10e2f1acd0106c Peter Zijlstra 2016-05-09 6155 * average idle time for this rq (as found in rq->avg_idle). 10e2f1acd0106c Peter Zijlstra 2016-05-09 6156 */ 10e2f1acd0106c Peter Zijlstra 2016-05-09 6157 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) 10e2f1acd0106c Peter Zijlstra 2016-05-09 6158 { b5cd7f229609cf Cheng Jian 2019-12-13 6159 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); 9cfb38a7ba5a9c Wanpeng Li 2016-10-09 6160 struct sched_domain *this_sd; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6161 u64 avg_cost, avg_idle; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6162 u64 time, cost; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6163 s64 delta; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6164 int cpu, nr = INT_MAX; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6165 9cfb38a7ba5a9c Wanpeng Li 2016-10-09 6166 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); 9cfb38a7ba5a9c Wanpeng Li 2016-10-09 6167 if (!this_sd) 9cfb38a7ba5a9c Wanpeng Li 2016-10-09 6168 return -1; 9cfb38a7ba5a9c Wanpeng Li 2016-10-09 6169 10e2f1acd0106c Peter Zijlstra 2016-05-09 6170 /* 10e2f1acd0106c Peter Zijlstra 2016-05-09 6171 * Due to large variance we need a large fuzz factor; hackbench in 10e2f1acd0106c Peter Zijlstra 2016-05-09 6172 * particularly is sensitive here. 10e2f1acd0106c Peter Zijlstra 2016-05-09 6173 */ 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6174 avg_idle = this_rq()->avg_idle / 512; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6175 avg_cost = this_sd->avg_scan_cost + 1; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6176 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6177 if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) 10e2f1acd0106c Peter Zijlstra 2016-05-09 6178 return -1; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6179 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6180 if (sched_feat(SIS_PROP)) { 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6181 u64 span_avg = sd->span_weight * avg_idle; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6182 if (span_avg > 4*avg_cost) 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6183 nr = div_u64(span_avg, avg_cost); 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6184 else 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6185 nr = 4; 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6186 } 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6187 10e2f1acd0106c Peter Zijlstra 2016-05-09 6188 time = local_clock(); 10e2f1acd0106c Peter Zijlstra 2016-05-09 6189 b5cd7f229609cf Cheng Jian 2019-12-13 @6190 cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); b5cd7f229609cf Cheng Jian 2019-12-13 6191 b5cd7f229609cf Cheng Jian 2019-12-13 6192 for_each_cpu_wrap(cpu, cpus, target) { 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6193 if (!--nr) 1ad3aaf3fcd244 Peter Zijlstra 2017-05-17 6194 return -1; 943d355d7feef3 Rohit Jain 2018-05-09 6195 if (available_idle_cpu(cpu)) 10e2f1acd0106c Peter Zijlstra 2016-05-09 6196 break; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6197 } 10e2f1acd0106c Peter Zijlstra 2016-05-09 6198 10e2f1acd0106c Peter Zijlstra 2016-05-09 6199 time = local_clock() - time; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6200 cost = this_sd->avg_scan_cost; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6201 delta = (s64)(time - cost) / 8; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6202 this_sd->avg_scan_cost += delta; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6203 10e2f1acd0106c Peter Zijlstra 2016-05-09 6204 return cpu; 10e2f1acd0106c Peter Zijlstra 2016-05-09 6205 } 10e2f1acd0106c Peter Zijlstra 2016-05-09 6206 :::::: The code at line 6190 was first introduced by commit :::::: b5cd7f229609cf328664aedb056a6fd744e0068b sched/fair: Optimize select_idle_cpu :::::: TO: Cheng Jian <cj.chengjian(a)huawei.com&gt; :::::: CC: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org