tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   abaf6f60176f1ae9d946d63e4db63164600b7b1a
commit: 784769f5b8efcd1920bde788a51e9ef69d1222b0 [11862/11865] Merge branch 'akpm-current/current'
config: x86_64-randconfig-r026-20210220 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project c9439ca36342fb6013187d0a69aef92736951476)
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 x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=784769f5b8efcd1920bde788a51e9ef69d1222b0
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout 784769f5b8efcd1920bde788a51e9ef69d1222b0
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

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

All errors (new ones prefixed by >>):

   In file included from <built-in>:3:
   In file included from drivers/gpu/drm/i915/display/intel_display_power.h:9:
   In file included from drivers/gpu/drm/i915/display/intel_display.h:28:
   In file included from include/drm/drm_util.h:36:
   In file included from include/linux/kgdb.h:19:
   In file included from include/linux/kprobes.h:29:
   In file included from include/linux/ftrace.h:12:
   In file included from include/linux/kallsyms.h:12:
   In file included from include/linux/mm.h:10:
>> include/linux/gfp.h:20:32: error: redefinition of typedef 'gfp_t' is a C11 feature [-Werror,-Wtypedef-redefinition]
   typedef unsigned int __bitwise gfp_t;   // repeated here for kernel-doc
                                  ^
   include/linux/types.h:148:32: note: previous definition is here
   typedef unsigned int __bitwise gfp_t;
                                  ^
   1 error generated.


vim +/gfp_t +20 include/linux/gfp.h

^1da177e4c3f41 Linus Torvalds          2005-04-16  10  
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  11) /**
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  12)  * typedef gfp_t - Memory allocation flags.
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  13)  *
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  14)  * GFP flags are commonly used throughout Linux to indicate how memory
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  15)  * should be allocated.  The GFP acronym stands for "get free pages",
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  16)  * the underlying memory allocation function.  Not every GFP flag is
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  17)  * supported by every function which may allocate memory.  Most users
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  18)  * will want to use a plain ``GFP_KERNEL``.
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  19)  */
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19 @20) typedef unsigned int __bitwise gfp_t;	// repeated here for kernel-doc
e8805271b82793 Matthew Wilcox (Oracle  2021-02-19  21) 

:::::: The code at line 20 was first introduced by commit
:::::: e8805271b82793e6d1f3de786c2278e4d622bdb6 mm/gfp: add kernel-doc for gfp_t

:::::: TO: Matthew Wilcox (Oracle) <willy@infradead.org>
:::::: CC: Stephen Rothwell <sfr@canb.auug.org.au>

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