Hi Michal,

[auto build test ERROR on next-20160229]
[also build test ERROR on v4.5-rc6]
[cannot apply to drm/drm-next drm-intel/for-linux-next v4.5-rc6 v4.5-rc5 v4.5-rc4]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Michal-Hocko/change-mmap_sem-taken-for-write-killable/20160229-213258
config: s390-allyesconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=s390 

All errors (new ones prefixed by >>):

   arch/s390/kernel/vdso.c: In function 'arch_setup_additional_pages':
>> arch/s390/kernel/vdso.c:219:2: error: implicit declaration of function 'down_write_killable' [-Werror=implicit-function-declaration]
     if (down_write_killable(&mm->mmap_sem))
     ^
   cc1: some warnings being treated as errors

vim +/down_write_killable +219 arch/s390/kernel/vdso.c

   213	
   214		/*
   215		 * pick a base address for the vDSO in process space. We try to put
   216		 * it at vdso_base which is the "natural" base for it, but we might
   217		 * fail and end up putting it elsewhere.
   218		 */
 > 219		if (down_write_killable(&mm->mmap_sem))
   220			return -EINTR;
   221		vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
   222		if (IS_ERR_VALUE(vdso_base)) {

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