[jolsa-perf:ftrace/direct 8/8] samples/ftrace/ftrace-direct-multi.c:8:6: error: no previous prototype for 'my_direct_func'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git ftrace/direct
head:   b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019
commit: b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019 [8/8] ftrace/samples: Add multi direct interface test module
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?id=b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019
        git remote add jolsa-perf https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
        git fetch --no-tags jolsa-perf ftrace/direct
        git checkout b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019
        # 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@xxxxxxxxx>

All errors (new ones prefixed by >>):

>> samples/ftrace/ftrace-direct-multi.c:8:6: error: no previous prototype for 'my_direct_func' [-Werror=missing-prototypes]
       8 | void my_direct_func(unsigned long ip)
         |      ^~~~~~~~~~~~~~
   cc1: all warnings being treated as errors


vim +/my_direct_func +8 samples/ftrace/ftrace-direct-multi.c

     7	
   > 8	void my_direct_func(unsigned long ip)
     9	{
    10		trace_printk("ip %lx\n", ip);
    11	}
    12	

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Attachment: .config.gz
Description: application/gzip