tree: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/membarrier head: df3b012fb56f54e581492d7ec053e36d4eacfabc commit: 77bac12bb7899853f4a19463b7e7ab1a7652666e [4/8] membarrier: Make the post-switch-mm barrier explicit config: alpha-randconfig-s031-20210617 (attached as .config) compiler: alpha-linux-gcc (GCC) 9.3.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # apt-get install sparse # sparse version: v0.6.3-341-g8af24329-dirty # 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/membarrier git checkout 77bac12bb7899853f4a19463b7e7ab1a7652666e # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=alpha 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: In function 'ttwu_stat': kernel/sched/core.c:2916:13: warning: variable 'rq' set but not used [-Wunused-but-set-variable] 2916 | struct rq *rq; | ^~ kernel/sched/core.c: In function 'finish_task_switch': kernel/sched/core.c:4225:5: error: 'If' undeclared (first use in this function) 4225 | * If an architecture needs to take a specific action for | ^~ kernel/sched/core.c:4225:5: note: each undeclared identifier is reported only once for each function it appears in kernel/sched/core.c:4225:7: error: expected ';' before 'an' 4225 | * If an architecture needs to take a specific action for | ^~~ | ; 4226 | * SYNC_CORE, it can do so in switch_mm_irqs_off(). | ^ In file included from include/linux/mmu_context.h:5, from kernel/sched/sched.h:55, from kernel/sched/core.c:13: arch/alpha/include/asm/mmu_context.h:225: note: macro "switch_mm" defined here 225 | # define switch_mm(a,b,c) ev5_switch_mm((a),(b),(c)) | kernel/sched/core.c:4174:20: warning: unused variable 'mm' [-Wunused-variable] 4174 | struct mm_struct *mm = rq->prev_mm; | ^~ vim +/switch_mm +4226 kernel/sched/core.c 4866cde064afbb kernel/sched.c Nicholas Piggin 2005-06-25 4150 ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4151 /** ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4152 * finish_task_switch - clean up after a task-switch ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4153 * @prev: the thread we just switched away from. ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4154 * 4866cde064afbb kernel/sched.c Nicholas Piggin 2005-06-25 4155 * finish_task_switch must be called after the context switch, paired 4866cde064afbb kernel/sched.c Nicholas Piggin 2005-06-25 4156 * with a prepare_task_switch call before the context switch. 4866cde064afbb kernel/sched.c Nicholas Piggin 2005-06-25 4157 * finish_task_switch will reconcile locking set up by prepare_task_switch, 4866cde064afbb kernel/sched.c Nicholas Piggin 2005-06-25 4158 * and do any other architecture-specific cleanup actions. ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4159 * ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4160 * Note that we may have delayed dropping an mm in context_switch(). If ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4161 * so, we finish that here outside of the runqueue lock. (Doing it ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4162 * with the lock held can cause deadlocks; see schedule() for ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4163 * details.) dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4164 * dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4165 * The context switch have flipped the stack from under us and restored the dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4166 * local variables which were saved when this task called schedule() in the dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4167 * past. prev == current is still correct but we need to recalculate this_rq dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4168 * because prev may have moved to another CPU. ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4169 */ dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4170 static struct rq *finish_task_switch(struct task_struct *prev) ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4171 __releases(rq->lock) ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4172 { dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4173 struct rq *rq = this_rq(); ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4174 struct mm_struct *mm = rq->prev_mm; 55a101f8f71a3d kernel/sched.c Oleg Nesterov 2006-09-29 4175 long prev_state; ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4176 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4177 /* 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4178 * The previous task will have left us with a preempt_count of 2 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4179 * because it left us after: 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4180 * 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4181 * schedule() 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4182 * preempt_disable(); // 1 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4183 * __schedule() 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4184 * raw_spin_lock_irq(&rq->lock) // 2 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4185 * 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4186 * Also, see FORK_PREEMPT_COUNT. 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4187 */ e2bf1c4b17aff2 kernel/sched/core.c Peter Zijlstra 2015-09-29 4188 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, e2bf1c4b17aff2 kernel/sched/core.c Peter Zijlstra 2015-09-29 4189 "corrupted preempt_count: %s/%d/0x%x\n", e2bf1c4b17aff2 kernel/sched/core.c Peter Zijlstra 2015-09-29 4190 current->comm, current->pid, preempt_count())) e2bf1c4b17aff2 kernel/sched/core.c Peter Zijlstra 2015-09-29 4191 preempt_count_set(FORK_PREEMPT_COUNT); 609ca066386b2e kernel/sched/core.c Peter Zijlstra 2015-09-28 4192 ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4193 rq->prev_mm = NULL; ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4194 ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4195 /* ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4196 * A task struct has one reference for the use as "current". c394cc9fbb367f kernel/sched.c Oleg Nesterov 2006-09-29 4197 * If a task dies, then it sets TASK_DEAD in tsk->state and calls 55a101f8f71a3d kernel/sched.c Oleg Nesterov 2006-09-29 4198 * schedule one last time. The schedule call will never return, and 55a101f8f71a3d kernel/sched.c Oleg Nesterov 2006-09-29 4199 * the scheduled task must drop that reference. 95913d97914f44 kernel/sched/core.c Peter Zijlstra 2015-09-29 4200 * 95913d97914f44 kernel/sched/core.c Peter Zijlstra 2015-09-29 4201 * We must observe prev->state before clearing prev->on_cpu (in 31cb1bc0dc9488 kernel/sched/core.c rodrigosiqueira 2017-12-15 4202 * finish_task), otherwise a concurrent wakeup can get prev 95913d97914f44 kernel/sched/core.c Peter Zijlstra 2015-09-29 4203 * running on another CPU and we could rave with its RUNNING -> DEAD 95913d97914f44 kernel/sched/core.c Peter Zijlstra 2015-09-29 4204 * transition, resulting in a double drop. ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4205 */ 55a101f8f71a3d kernel/sched.c Oleg Nesterov 2006-09-29 4206 prev_state = prev->state; bf9fae9f5e4ca8 kernel/sched/core.c Frederic Weisbecker 2012-09-08 4207 vtime_task_switch(prev); a8d757ef076f0f kernel/sched.c Stephane Eranian 2011-08-25 4208 perf_event_task_sched_in(prev, current); 31cb1bc0dc9488 kernel/sched/core.c rodrigosiqueira 2017-12-15 4209 finish_task(prev); 31cb1bc0dc9488 kernel/sched/core.c rodrigosiqueira 2017-12-15 4210 finish_lock_switch(rq); 01f23e1630d944 kernel/sched/core.c Catalin Marinas 2011-11-27 4211 finish_arch_post_lock_switch(); 0ed557aa813922 kernel/sched/core.c Mark Rutland 2018-06-14 4212 kcov_finish_switch(current); 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4213 /* 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4214 * kmap_local_sched_out() is invoked with rq::lock held and 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4215 * interrupts disabled. There is no requirement for that, but the 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4216 * sched out code does not have an interrupt enabled section. 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4217 * Restoring the maps on sched in does not require interrupts being 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4218 * disabled either. 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4219 */ 5fbda3ecd14a53 kernel/sched/core.c Thomas Gleixner 2020-11-18 4220 kmap_local_sched_in(); e8fa136262e112 kernel/sched.c Steven Rostedt 2008-01-25 4221 e107be36efb2a2 kernel/sched.c Avi Kivity 2007-07-26 4222 fire_sched_in_preempt_notifiers(current); 9f81d011fbe6ff kernel/sched/core.c Andy Lutomirski 2020-12-02 4223 70216e18e519a5 kernel/sched/core.c Mathieu Desnoyers 2018-01-29 4224 * 9f81d011fbe6ff kernel/sched/core.c Andy Lutomirski 2020-12-02 @4225 * If an architecture needs to take a specific action for 9f81d011fbe6ff kernel/sched/core.c Andy Lutomirski 2020-12-02 @4226 * SYNC_CORE, it can do so in switch_mm_irqs_off(). 9f81d011fbe6ff kernel/sched/core.c Andy Lutomirski 2020-12-02 4227 if (mm) ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4228 mmdrop(mm); 9f81d011fbe6ff kernel/sched/core.c Andy Lutomirski 2020-12-02 4229 1cef1150ef40ec kernel/sched/core.c Peter Zijlstra 2018-06-07 4230 if (unlikely(prev_state == TASK_DEAD)) { e6c390f2dfd04c kernel/sched/core.c Dario Faggioli 2013-11-07 4231 if (prev->sched_class->task_dead) e6c390f2dfd04c kernel/sched/core.c Dario Faggioli 2013-11-07 4232 prev->sched_class->task_dead(prev); e6c390f2dfd04c kernel/sched/core.c Dario Faggioli 2013-11-07 4233 c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4234 /* c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4235 * Remove function-return probe instances associated with this c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4236 * task and put them back on the free list. c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4237 */ c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4238 kprobe_flush_task(prev); 68f24b08ee892d kernel/sched/core.c Andy Lutomirski 2016-09-15 4239 68f24b08ee892d kernel/sched/core.c Andy Lutomirski 2016-09-15 4240 /* Task is done with its stack. */ 68f24b08ee892d kernel/sched/core.c Andy Lutomirski 2016-09-15 4241 put_task_stack(prev); 68f24b08ee892d kernel/sched/core.c Andy Lutomirski 2016-09-15 4242 0ff7b2cfbae36e kernel/sched/core.c Eric W. Biederman 2019-09-14 4243 put_task_struct_rcu_user(prev); ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4244 } 99e5ada9407cc1 kernel/sched/core.c Frederic Weisbecker 2013-04-20 4245 de734f89b67c2d kernel/sched/core.c Frederic Weisbecker 2015-06-11 4246 tick_nohz_task_switch(); dfa50b605c2a93 kernel/sched/core.c Oleg Nesterov 2014-10-09 4247 return rq; c6fd91f0bdcd29 kernel/sched.c bibo mao 2006-03-26 4248 } ^1da177e4c3f41 kernel/sched.c Linus Torvalds 2005-04-16 4249 :::::: The code at line 4226 was first introduced by commit :::::: 9f81d011fbe6ff333c5a68e317d7ed7835db699d x86/mm: Handle unlazying membarrier core sync in the arch code :::::: TO: Andy Lutomirski <luto(a)kernel.org&gt; :::::: CC: Andy Lutomirski <luto(a)kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org