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-m001-20211118 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Reported-by: Dan Carpenter <dan.carpenter(a)oracle.com&gt; smatch warnings: kernel/sched/core.c:4982 __change_current_mm() error: uninitialized symbol 'old_active_mm'. vim +/old_active_mm +4982 kernel/sched/core.c 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4938 void __change_current_mm(struct mm_struct *mm, bool mm_is_brand_new) 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4939 { 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4940 struct task_struct *tsk = current; 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4941 struct mm_struct *old_active_mm, *mm_to_drop = NULL; 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4942 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4943 BUG_ON(!mm); /* likely to cause corruption if we continue */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4944 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4945 /* 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4946 * We do not want to schedule, nor should procfs peek at current->mm 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4947 * while we're modifying it. task_lock() disables preemption and 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4948 * locks against procfs. 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4949 */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4950 task_lock(tsk); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4951 /* 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4952 * membarrier() requires a full barrier before switching mm. 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4953 */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4954 smp_mb__after_spinlock(); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4955 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4956 local_irq_disable(); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4957 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4958 if (tsk->mm) { 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4959 /* We're detaching from an old mm. Sync stats. */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4960 sync_mm_rss(tsk->mm); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4961 } else { 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4962 /* 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4963 * Switching from kernel mm to user. Drop the old lazy 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4964 * mm reference. 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4965 */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4966 mm_to_drop = tsk->active_mm; 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4967 } 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4968 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4969 tsk->active_mm = mm; 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4970 WRITE_ONCE(tsk->mm, mm); /* membarrier reads this without locks */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4971 membarrier_update_current_mm(mm); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4972 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4973 if (mm_is_brand_new) { 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4974 /* 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4975 * For historical reasons, some architectures want IRQs on 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4976 * when activate_mm() is called. If we're going to call 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4977 * activate_mm(), turn on IRQs but leave preemption 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4978 * disabled. 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4979 */ 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4980 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4981 local_irq_enable(); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 @4982 activate_mm(old_active_mm, mm); "old_active_mm" is never initialized. 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4983 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4984 local_irq_enable(); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4985 } else { 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4986 switch_mm_irqs_off(old_active_mm, mm, tsk); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4987 local_irq_enable(); 4863118ffa6fe6 kernel/sched/core.c Andy Lutomirski 2021-09-03 4988 } --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org