tree: https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git 20211117-sysctl-cleanups-all-set-04 head: 3559bb8939dd93c96215ab179d868c5fdc167335 commit: 99f50ec2e9ced923150fa9f7d6d9a5f767cba59c [22/36] printk: move printk sysctl to printk/sysctl.c config: arm-randconfig-r012-20211118 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project c46becf500df2a7fb4b4fce16178a036c344315a) 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 # install arm cross compiling tool for clang build # apt-get install binutils-arm-linux-gnueabi # https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/com... git remote add mcgrof-next https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git git fetch --no-tags mcgrof-next 20211117-sysctl-cleanups-all-set-04 git checkout 99f50ec2e9ced923150fa9f7d6d9a5f767cba59c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=arm If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>): kernel/printk/printk.c:175:5: warning: no previous prototype for function 'devkmsg_sysctl_set_loglvl' [-Wmissing-prototypes] int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, ^ kernel/printk/printk.c:175:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, ^ static printk_sysctl_init(); ^ kernel/printk/printk.c:3205:2: note: did you mean 'printk_late_init'? kernel/printk/printk.c:3174:19: note: 'printk_late_init' declared here static int __init printk_late_init(void) ^ 1 warning and 1 error generated. -- .data = &printk_delay_msec, ^ .proc_handler = devkmsg_sysctl_set_loglvl, ^ .data = &dmesg_restrict, ^~~~~~~~~~~~~~ kptr_restrict include/linux/printk.h:324:12: note: 'kptr_restrict' declared here extern int kptr_restrict; ^ void __init printk_sysctl_init(void) ^ kernel/printk/sysctl.c:82:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __init printk_sysctl_init(void) ^ static 1 warning and 3 errors generated. vim +/printk_sysctl_init +3205 kernel/printk/printk.c 3159 3160 /* 3161 * Some boot consoles access data that is in the init section and which will 3162 * be discarded after the initcalls have been run. To make sure that no code 3163 * will access this data, unregister the boot consoles in a late initcall. 3164 * 3165 * If for some reason, such as deferred probe or the driver being a loadable 3166 * module, the real console hasn't registered yet at this point, there will 3167 * be a brief interval in which no messages are logged to the console, which 3168 * makes it difficult to diagnose problems that occur during this time. 3169 * 3170 * To mitigate this problem somewhat, only unregister consoles whose memory 3171 * intersects with the init section. Note that all other boot consoles will 3172 * get unregistered when the real preferred console is registered. 3173 */ 3174 static int __init printk_late_init(void) 3175 { 3176 struct console *con; 3177 int ret; 3178 3179 for_each_console(con) { 3180 if (!(con->flags & CON_BOOT)) 3181 continue; 3182 3183 /* Check addresses that might be used for enabled consoles. */ 3184 if (init_section_intersects(con, sizeof(*con)) || 3185 init_section_contains(con->write, 0) || 3186 init_section_contains(con->read, 0) || 3187 init_section_contains(con->device, 0) || 3188 init_section_contains(con->unblank, 0) || 3189 init_section_contains(con->data, 0)) { 3190 /* 3191 * Please, consider moving the reported consoles out 3192 * of the init section. 3193 */ 3194 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", 3195 con->name, con->index); 3196 unregister_console(con); 3197 } 3198 } 3199 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, 3200 console_cpu_notify); 3201 WARN_ON(ret < 0); 3202 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", 3203 console_cpu_notify, NULL); 3204 WARN_ON(ret < 0); 3206 return 0; 3207 } 3208 late_initcall(printk_late_init); 3209 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org