tree: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/fixes head: 087ddc16a1dd1d4cb567859f56eb0b28ef65ee6c commit: 4def0489e2ed12c2280087e780bd67995b5cc537 [10/17] membarrier: Make the post-switch-mm barrier explicit config: x86_64-randconfig-a006-20210209 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # 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 x86/fixes git checkout 4def0489e2ed12c2280087e780bd67995b5cc537 # save the attached .config to linux build tree make 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 errors (new ones prefixed by >>): kernel/sched/core.c:2835:6: warning: no previous prototype for 'sched_set_stop_task' [-Wmissing-prototypes] 2835 | void sched_set_stop_task(int cpu, struct task_struct *stop) | ^~~~~~~~~~~~~~~~~~~ kernel/sched/core.c: In function 'schedule_tail': kernel/sched/core.c:4240:13: warning: variable 'rq' set but not used [-Wunused-but-set-variable] 4240 | struct rq *rq; | ^~ kernel/sched/core.c: In function 'context_switch': 4300 | membarrier_finish_switch_mm(rq->membarrier_state); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ | membarrier_switch_mm kernel/sched/core.c:4300:33: error: 'struct rq' has no member named 'membarrier_state' 4300 | membarrier_finish_switch_mm(rq->membarrier_state); | ^~ cc1: some warnings being treated as errors vim +4300 kernel/sched/core.c 4259 4260 /* 4261 * context_switch - switch to the new MM and the new thread's register state. 4262 */ 4263 static __always_inline struct rq * 4264 context_switch(struct rq *rq, struct task_struct *prev, 4265 struct task_struct *next, struct rq_flags *rf) 4266 { 4267 prepare_task_switch(rq, prev, next); 4268 4269 /* 4270 * For paravirt, this is coupled with an exit in switch_to to 4271 * combine the page table reload and the switch backend into 4272 * one hypercall. 4273 */ 4274 arch_start_context_switch(prev); 4275 4276 /* 4277 * kernel -> kernel lazy + transfer active 4278 * user -> kernel lazy + mmgrab() active 4279 * 4280 * kernel -> user switch + mmdrop() active 4281 * user -> user switch 4282 */ 4283 if (!next->mm) { // to kernel 4284 enter_lazy_tlb(prev->active_mm, next); 4285 4286 next->active_mm = prev->active_mm; 4287 if (prev->mm) // from user 4288 mmgrab(prev->active_mm); 4289 else 4290 prev->active_mm = NULL; 4291 } else { // to user 4292 membarrier_switch_mm(rq, prev->active_mm, next->mm); 4293 switch_mm_irqs_off(prev->active_mm, next->mm, next); 4294 4295 /* 4296 * sys_membarrier() requires an smp_mb() between setting 4297 * rq->curr->mm to a membarrier-enabled mm and returning 4298 * to userspace. 4299 */ 4301 4302 if (!prev->mm) { // from kernel 4303 /* will mmdrop() in finish_task_switch(). */ 4304 rq->prev_mm = prev->active_mm; 4305 prev->active_mm = NULL; 4306 } 4307 } 4308 4309 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); 4310 4311 prepare_lock_switch(rq, next, rf); 4312 4313 /* Here we just switch the register state and the stack. */ 4314 switch_to(prev, next, prev); 4315 barrier(); 4316 4317 return finish_task_switch(prev); 4318 } 4319 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org