tree:   https://github.com/intel/linux-intel-lts.git 5.4/preempt-rt
head:   bb4ae19664a898236b2af46b45a6a0fea23ab20d
commit: 7bc82c4f1b47c643468c3be1d9e0309d7c3e9b3f [3/13] Merge remote-tracking branch 'origin/5.4/yocto' into lts2019/yocto-rt
config: microblaze-randconfig-r005-20210517 (attached as .config)
compiler: microblaze-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://github.com/intel/linux-intel-lts/commit/7bc82c4f1b47c643468c3be1d9e0309d7c3e9b3f
        git remote add intel-linux-intel-lts https://github.com/intel/linux-intel-lts.git
        git fetch --no-tags intel-linux-intel-lts 5.4/preempt-rt
        git checkout 7bc82c4f1b47c643468c3be1d9e0309d7c3e9b3f
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=microblaze 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> kernel/printk/printk.c:1982:5: warning: no previous prototype for 'vprintk_default' [-Wmissing-prototypes]
    1982 | int vprintk_default(const char *fmt, va_list args)
         |     ^~~~~~~~~~~~~~~
   kernel/printk/printk.c: In function 'vprintk_default':
>> kernel/printk/printk.c:1993:2: warning: function 'vprintk_default' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    1993 |  r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
         |  ^
   kernel/printk/printk.c: In function 'vprintk_deferred':
>> kernel/printk/printk.c:2751:2: warning: function 'vprintk_deferred' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    2751 |  return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
         |  ^~~~~~


vim +/vprintk_default +1982 kernel/printk/printk.c

^1da177e4c3f41 kernel/printk.c        Linus Torvalds           2005-04-16  1981  
a0cba2179ea4c1 kernel/printk/printk.c Linus Torvalds           2016-08-09 @1982  int vprintk_default(const char *fmt, va_list args)
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1983) {
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1984) 	int r;
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1985) 
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1986) #ifdef CONFIG_KGDB_KDB
34aaff40b42148 kernel/printk/printk.c Petr Mladek              2016-12-14  1987  	/* Allow to pass printk() to kdb but avoid a recursion. */
34aaff40b42148 kernel/printk/printk.c Petr Mladek              2016-12-14  1988  	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
f7d4ca8bbfda23 kernel/printk/printk.c Daniel Thompson          2014-11-07  1989  		r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1990) 		return r;
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1991) 	}
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1992) #endif
a0cba2179ea4c1 kernel/printk/printk.c Linus Torvalds           2016-08-09 @1993  	r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1994) 
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1995) 	return r;
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1996) }
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1997) EXPORT_SYMBOL_GPL(vprintk_default);
afdc34a3d3b823 kernel/printk/printk.c Steven Rostedt (Red Hat  2014-06-19  1998) 

:::::: The code@line 1982 was first introduced by commit
:::::: a0cba2179ea4c1820fce2ee046b6ed90ecc56196 Revert "printk: create pr_<level> functions"

:::::: TO: Linus Torvalds <torvalds@linux-foundation.org>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org