stacktrace.c:undefined reference to `save_stack_trace'

[kbuild test robot]

Hi Chenwandun,

It's probably a bug fix that unveils the link errors.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   81b6b96475ac7a4ebfceae9f16fb3758327adbfe
commit: 68acde7629d75d460760a3124c52f358eecc6d26 drm/dp_mst: fix gcc compile error
date:   4 weeks ago
config: m68k-allmodconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 68acde7629d75d460760a3124c52f358eecc6d26
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=m68k 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

   kernel/stacktrace.o: In function `stack_trace_save':
>> stacktrace.c:(.text+0x120): undefined reference to `save_stack_trace'

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0-DAY kernel test infrastructure                 Open Source Technology Center
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Attachment: .config.gz
Description: application/gzip