tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/dev head: 3cd375aa70d563fe8aa3e5f03280bdd8a334de45 commit: 2c773bcaf4dd5031d0b2c980cc623ecfbcc6ab62 [80/85] squash! srcu: Make Tree SRCU able to operate without snp_node array config: arc-randconfig-r043-20220124 (https://download.01.org/0day-ci/archive/20220125/202201251951.fCJTBQJd-lk...) compiler: arc-elf-gcc (GCC) 11.2.0 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/ammarfaizi2/linux-block/commit/2c773bcaf4dd5031d0b2c98... git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/dev git checkout 2c773bcaf4dd5031d0b2c980cc623ecfbcc6ab62 # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arc SHELL=/bin/bash kernel/rcu/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/rcu/srcutree.c: In function 'srcu_barrier': 1168 | struct srcu_data *sdp; | ^~~ vim +/sdp +1168 kernel/rcu/srcutree.c 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1160 dad81a2026841b Paul E. McKenney 2017-03-25 1161 /** dad81a2026841b Paul E. McKenney 2017-03-25 1162 * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1163 * @ssp: srcu_struct on which to wait for in-flight callbacks. dad81a2026841b Paul E. McKenney 2017-03-25 1164 */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1165 void srcu_barrier(struct srcu_struct *ssp) dad81a2026841b Paul E. McKenney 2017-03-25 1166 { da915ad5cf25b5 Paul E. McKenney 2017-04-05 1167 int cpu; da915ad5cf25b5 Paul E. McKenney 2017-04-05 @1168 struct srcu_data *sdp; aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1169 unsigned long s = rcu_seq_snap(&ssp->srcu_barrier_seq); da915ad5cf25b5 Paul E. McKenney 2017-04-05 1170 aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1171 check_init_srcu_struct(ssp); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1172 mutex_lock(&ssp->srcu_barrier_mutex); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1173 if (rcu_seq_done(&ssp->srcu_barrier_seq, s)) { da915ad5cf25b5 Paul E. McKenney 2017-04-05 1174 smp_mb(); /* Force ordering following return. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1175 mutex_unlock(&ssp->srcu_barrier_mutex); da915ad5cf25b5 Paul E. McKenney 2017-04-05 1176 return; /* Someone else did our work for us. */ da915ad5cf25b5 Paul E. McKenney 2017-04-05 1177 } aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1178 rcu_seq_start(&ssp->srcu_barrier_seq); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1179 init_completion(&ssp->srcu_barrier_completion); da915ad5cf25b5 Paul E. McKenney 2017-04-05 1180 da915ad5cf25b5 Paul E. McKenney 2017-04-05 1181 /* Initial count prevents reaching zero until all CBs are posted. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1182 atomic_set(&ssp->srcu_barrier_cpu_cnt, 1); da915ad5cf25b5 Paul E. McKenney 2017-04-05 1183 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1184 if (!smp_load_acquire(&ssp->srcu_size_state)) { 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1185 srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, 0)); 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1186 } else { 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1187 da915ad5cf25b5 Paul E. McKenney 2017-04-05 1188 /* da915ad5cf25b5 Paul E. McKenney 2017-04-05 1189 * Each pass through this loop enqueues a callback, but only da915ad5cf25b5 Paul E. McKenney 2017-04-05 1190 * on CPUs already having callbacks enqueued. Note that if da915ad5cf25b5 Paul E. McKenney 2017-04-05 1191 * a CPU already has callbacks enqueue, it must have already da915ad5cf25b5 Paul E. McKenney 2017-04-05 1192 * registered the need for a future grace period, so all we da915ad5cf25b5 Paul E. McKenney 2017-04-05 1193 * need do is enqueue a callback that will use the same da915ad5cf25b5 Paul E. McKenney 2017-04-05 1194 * grace period as the last callback already in the queue. da915ad5cf25b5 Paul E. McKenney 2017-04-05 1195 */ da915ad5cf25b5 Paul E. McKenney 2017-04-05 1196 for_each_possible_cpu(cpu) { aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1197 sdp = per_cpu_ptr(ssp->sda, cpu); 2c773bcaf4dd50 Paul E. McKenney 2022-01-24 1198 srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu)); a602538e46c9c6 Paul E. McKenney 2017-04-28 1199 } da915ad5cf25b5 Paul E. McKenney 2017-04-05 1200 } da915ad5cf25b5 Paul E. McKenney 2017-04-05 1201 da915ad5cf25b5 Paul E. McKenney 2017-04-05 1202 /* Remove the initial count, at which point reaching zero can happen. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1203 if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt)) aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1204 complete(&ssp->srcu_barrier_completion); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1205 wait_for_completion(&ssp->srcu_barrier_completion); da915ad5cf25b5 Paul E. McKenney 2017-04-05 1206 aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1207 rcu_seq_end(&ssp->srcu_barrier_seq); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1208 mutex_unlock(&ssp->srcu_barrier_mutex); dad81a2026841b Paul E. McKenney 2017-03-25 1209 } dad81a2026841b Paul E. McKenney 2017-03-25 1210 EXPORT_SYMBOL_GPL(srcu_barrier); dad81a2026841b Paul E. McKenney 2017-03-25 1211 :::::: The code at line 1168 was first introduced by commit :::::: da915ad5cf25b5f5d358dd3670c3378d8ae8c03e srcu: Parallelize callback handling :::::: TO: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com&gt; :::::: CC: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org