Hi Nicholas, I love your patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on v5.10 next-20201217] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Nicholas-Piggin/powerpc-64s-TLB-... base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: powerpc-randconfig-m031-20201217 (attached as .config) compiler: powerpc64le-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://github.com/0day-ci/linux/commit/5bd02bea3da4e21fa00729e7687fc93a5... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Nicholas-Piggin/powerpc-64s-TLB-flushing-improvements/20201217-220230 git checkout 5bd02bea3da4e21fa00729e7687fc93a5c653e2b # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): 646 | void exit_lazy_flush_tlb(struct mm_struct *mm, bool always_flush) | ^~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors vim +/exit_lazy_flush_tlb +646 arch/powerpc/mm/book3s64/radix_tlb.c 641 642 /* 643 * If always_flush is true, then flush even if this CPU can't be removed 644 * from mm_cpumask. 645 */ 647 { 648 unsigned long pid = mm->context.id; 649 int cpu = smp_processor_id(); 650 651 /* 652 * A kthread could have done a mmget_not_zero() after the flushing CPU 653 * checked mm_cpumask, and be in the process of kthread_use_mm when 654 * interrupted here. In that case, current->mm will be set to mm, 655 * because kthread_use_mm() setting ->mm and switching to the mm is 656 * done with interrupts off. 657 */ 658 if (current->mm == mm) 659 goto out; 660 661 if (current->active_mm == mm) { 662 WARN_ON_ONCE(current->mm != NULL); 663 /* Is a kernel thread and is using mm as the lazy tlb */ 664 mmgrab(&init_mm); 665 current->active_mm = &init_mm; 666 switch_mm_irqs_off(mm, &init_mm, current); 667 mmdrop(mm); 668 } 669 670 /* 671 * This IPI may be initiated from any source including those not 672 * running the mm, so there may be a racing IPI that comes after 673 * this one which finds the cpumask already clear. Check and avoid 674 * underflowing the active_cpus count in that case. The race should 675 * not otherwise be a problem, but the TLB must be flushed because 676 * that's what the caller expects. 677 */ 678 if (cpumask_test_cpu(cpu, mm_cpumask(mm))) { 679 atomic_dec(&mm->context.active_cpus); 680 cpumask_clear_cpu(cpu, mm_cpumask(mm)); 681 always_flush = true; 682 } 683 684 out: 685 if (always_flush) 686 _tlbiel_pid(pid, RIC_FLUSH_ALL); 687 } 688 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org