tree: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git sched/lazymm head: c0d03d4f2778fd0a7c16e69cdfb3f111296129b5 commit: 4863118ffa6fe6af7cfb18c4d4ee6434537b0c8b [13/16] sched, exec: Factor current mm changes out from exec config: x86_64-randconfig-r034-20211116 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project fbe72e41b99dc7994daac300d208a955be3e4a0a) 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/luto/linux.git/commit/?id... git remote add luto https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git git fetch --no-tags luto sched/lazymm git checkout 4863118ffa6fe6af7cfb18c4d4ee6434537b0c8b # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 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/core.c:3417:6: warning: no previous prototype for function 'sched_set_stop_task' [-Wmissing-prototypes] void sched_set_stop_task(int cpu, struct task_struct *stop) ^ kernel/sched/core.c:3417:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void sched_set_stop_task(int cpu, struct task_struct *stop) ^ static switch_mm_irqs_off(old_active_mm, mm, tsk); ^~~~~~~~~~~~~ kernel/sched/core.c:4941:33: note: initialize the variable 'old_active_mm' to silence this warning struct mm_struct *old_active_mm, *mm_to_drop = NULL; ^ = NULL 2 warnings generated. vim +/old_active_mm +4986 kernel/sched/core.c 4937 4938 void __change_current_mm(struct mm_struct *mm, bool mm_is_brand_new) 4939 { 4940 struct task_struct *tsk = current; 4941 struct mm_struct *old_active_mm, *mm_to_drop = NULL; 4942 4943 BUG_ON(!mm); /* likely to cause corruption if we continue */ 4944 4945 /* 4946 * We do not want to schedule, nor should procfs peek at current->mm 4947 * while we're modifying it. task_lock() disables preemption and 4948 * locks against procfs. 4949 */ 4950 task_lock(tsk); 4951 /* 4952 * membarrier() requires a full barrier before switching mm. 4953 */ 4954 smp_mb__after_spinlock(); 4955 4956 local_irq_disable(); 4957 4958 if (tsk->mm) { 4959 /* We're detaching from an old mm. Sync stats. */ 4960 sync_mm_rss(tsk->mm); 4961 } else { 4962 /* 4963 * Switching from kernel mm to user. Drop the old lazy 4964 * mm reference. 4965 */ 4966 mm_to_drop = tsk->active_mm; 4967 } 4968 4969 tsk->active_mm = mm; 4970 WRITE_ONCE(tsk->mm, mm); /* membarrier reads this without locks */ 4971 membarrier_update_current_mm(mm); 4972 4973 if (mm_is_brand_new) { 4974 /* 4975 * For historical reasons, some architectures want IRQs on 4976 * when activate_mm() is called. If we're going to call 4977 * activate_mm(), turn on IRQs but leave preemption 4978 * disabled. 4979 */ 4980 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 4981 local_irq_enable(); 4982 activate_mm(old_active_mm, mm); 4983 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 4984 local_irq_enable(); 4985 } else { 4987 local_irq_enable(); 4988 } 4989 4990 /* IRQs are on now. Preemption is still disabled by task_lock(). */ 4991 4992 membarrier_finish_switch_mm(mm); 4993 vmacache_flush(tsk); 4994 task_unlock(tsk); 4995 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org