tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.4.y head: 95a3867e897abd7811196123f81a119a75aba863 commit: e3484129eb0f7c67c85868d1584f1e6335e86efa [7217/9999] MIPS: VDSO: Prevent use of smp_processor_id() config: mips-malta_kvm_defconfig (attached as .config) compiler: mipsel-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-4.4.y git checkout e3484129eb0f7c67c85868d1584f1e6335e86efa # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips 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 >>): arch/mips/kernel/smp.c:156:17: error: no previous prototype for 'start_secondary' [-Werror=missing-prototypes] 156 | asmlinkage void start_secondary(void) | ^~~~~~~~~~~~~~~ arch/mips/kernel/smp.c:278:5: error: no previous prototype for 'setup_profiling_timer' [-Werror=missing-prototypes] 278 | int setup_profiling_timer(unsigned int multiplier) | ^~~~~~~~~~~~~~~~~~~~~ In file included from arch/mips/include/asm/processor.h:14, from arch/mips/include/asm/thread_info.h:15, from include/linux/thread_info.h:54, from include/asm-generic/preempt.h:4, from arch/mips/include/generated/asm/preempt.h:1, from include/linux/preempt.h:59, from include/linux/interrupt.h:8, from arch/mips/kernel/smp.c:24: arch/mips/kernel/smp.c: In function 'flush_tlb_mm': include/linux/cpumask.h:221:9: error: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Werror=sign-compare] 221 | (cpu) < nr_cpu_ids;) | ^ include/linux/cpumask.h:725:36: note: in expansion of macro 'for_each_cpu' 725 | #define for_each_online_cpu(cpu) for_each_cpu((cpu), cpu_online_mask) | ^~~~~~~~~~~~ arch/mips/kernel/smp.c:343:3: note: in expansion of macro 'for_each_online_cpu' 343 | for_each_online_cpu(cpu) { | ^~~~~~~~~~~~~~~~~~~ 344 | if (cpu != smp_processor_id() && cpu_context(cpu, mm)) | ^~ In file included from arch/mips/include/asm/processor.h:14, from arch/mips/include/asm/thread_info.h:15, from include/linux/thread_info.h:54, from include/asm-generic/preempt.h:4, from arch/mips/include/generated/asm/preempt.h:1, from include/linux/preempt.h:59, from include/linux/interrupt.h:8, from arch/mips/kernel/smp.c:24: arch/mips/kernel/smp.c: In function 'flush_tlb_range': include/linux/cpumask.h:221:9: error: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Werror=sign-compare] 221 | (cpu) < nr_cpu_ids;) | ^ include/linux/cpumask.h:725:36: note: in expansion of macro 'for_each_cpu' 725 | #define for_each_online_cpu(cpu) for_each_cpu((cpu), cpu_online_mask) | ^~~~~~~~~~~~ arch/mips/kernel/smp.c:382:3: note: in expansion of macro 'for_each_online_cpu' 382 | for_each_online_cpu(cpu) { | ^~~~~~~~~~~~~~~~~~~ arch/mips/kernel/smp.c:383:12: error: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Werror=sign-compare] 383 | if (cpu != smp_processor_id() && cpu_context(cpu, mm)) | ^~ In file included from arch/mips/include/asm/processor.h:14, from arch/mips/include/asm/thread_info.h:15, from include/linux/thread_info.h:54, from include/asm-generic/preempt.h:4, from arch/mips/include/generated/asm/preempt.h:1, from include/linux/preempt.h:59, from include/linux/interrupt.h:8, from arch/mips/kernel/smp.c:24: arch/mips/kernel/smp.c: In function 'flush_tlb_page': include/linux/cpumask.h:221:9: error: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Werror=sign-compare] 221 | (cpu) < nr_cpu_ids;) | ^ include/linux/cpumask.h:725:36: note: in expansion of macro 'for_each_cpu' 725 | #define for_each_online_cpu(cpu) for_each_cpu((cpu), cpu_online_mask) | ^~~~~~~~~~~~ arch/mips/kernel/smp.c:428:3: note: in expansion of macro 'for_each_online_cpu' 428 | for_each_online_cpu(cpu) { | ^~~~~~~~~~~~~~~~~~~ arch/mips/kernel/smp.c:429:12: error: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Werror=sign-compare] 429 | if (cpu != smp_processor_id() && cpu_context(cpu, vma->vm_mm)) | ^~ cc1: all warnings being treated as errors vim +344 arch/mips/kernel/smp.c 25969354a385f3 Ralf Baechle 2006-06-22 320 ^1da177e4c3f41 Linus Torvalds 2005-04-16 321 /* ^1da177e4c3f41 Linus Torvalds 2005-04-16 322 * The following tlb flush calls are invoked when old translations are ^1da177e4c3f41 Linus Torvalds 2005-04-16 323 * being torn down, or pte attributes are changing. For single threaded ^1da177e4c3f41 Linus Torvalds 2005-04-16 324 * address spaces, a new context is obtained on the current cpu, and tlb ^1da177e4c3f41 Linus Torvalds 2005-04-16 325 * context on other cpus are invalidated to force a new context allocation ^1da177e4c3f41 Linus Torvalds 2005-04-16 326 * at switch_mm time, should the mm ever be used on other cpus. For ^1da177e4c3f41 Linus Torvalds 2005-04-16 327 * multithreaded address spaces, intercpu interrupts have to be sent. ^1da177e4c3f41 Linus Torvalds 2005-04-16 328 * Another case where intercpu interrupts are required is when the target ^1da177e4c3f41 Linus Torvalds 2005-04-16 329 * mm might be active on another cpu (eg debuggers doing the flushes on ^1da177e4c3f41 Linus Torvalds 2005-04-16 330 * behalf of debugees, kswapd stealing pages from another process etc). ^1da177e4c3f41 Linus Torvalds 2005-04-16 331 * Kanoj 07/00. ^1da177e4c3f41 Linus Torvalds 2005-04-16 332 */ ^1da177e4c3f41 Linus Torvalds 2005-04-16 333 ^1da177e4c3f41 Linus Torvalds 2005-04-16 334 void flush_tlb_mm(struct mm_struct *mm) ^1da177e4c3f41 Linus Torvalds 2005-04-16 335 { ^1da177e4c3f41 Linus Torvalds 2005-04-16 336 preempt_disable(); ^1da177e4c3f41 Linus Torvalds 2005-04-16 337 ^1da177e4c3f41 Linus Torvalds 2005-04-16 338 if ((atomic_read(&mm->mm_users) != 1) || (current->mm != mm)) { c50cade95b075e Ralf Baechle 2007-10-04 339 smp_on_other_tlbs(flush_tlb_mm_ipi, mm); ^1da177e4c3f41 Linus Torvalds 2005-04-16 340 } else { b5eb5511453953 Ralf Baechle 2007-10-03 341 unsigned int cpu; b5eb5511453953 Ralf Baechle 2007-10-03 342 0b5f9c005def15 Rusty Russell 2012-03-29 343 for_each_online_cpu(cpu) { 0b5f9c005def15 Rusty Russell 2012-03-29 @344 if (cpu != smp_processor_id() && cpu_context(cpu, mm)) b5eb5511453953 Ralf Baechle 2007-10-03 345 cpu_context(cpu, mm) = 0; ^1da177e4c3f41 Linus Torvalds 2005-04-16 346 } 0b5f9c005def15 Rusty Russell 2012-03-29 347 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 348 local_flush_tlb_mm(mm); ^1da177e4c3f41 Linus Torvalds 2005-04-16 349 ^1da177e4c3f41 Linus Torvalds 2005-04-16 350 preempt_enable(); ^1da177e4c3f41 Linus Torvalds 2005-04-16 351 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 352 :::::: The code at line 344 was first introduced by commit :::::: 0b5f9c005def154f9c21f9be0223b65b50d54368 remove references to cpu_*_map in arch/ :::::: TO: Rusty Russell <rusty(a)rustcorp.com.au&gt; :::::: CC: Rusty Russell <rusty(a)rustcorp.com.au&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org