tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master
head:   0747bb04956d8614b67a01df63d65d28879a955a
commit: 7c8cd4b433697f9d2b9b268a0ca181c534a49c7b [31/36] Merge branch 'timers/core'
config: um-i386_defconfig (attached as .config)
compiler: gcc-7 (Debian 7.5.0-5) 7.5.0
reproduce:
        git checkout 7c8cd4b433697f9d2b9b268a0ca181c534a49c7b
        # save the attached .config to linux build tree
        make ARCH=um SUBARCH=i386

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

All errors (new ones prefixed by >>):

   In file included from include/vdso/processor.h:10:0,
                    from include/vdso/datapage.h:17,
                    from arch/x86/include/asm/vgtod.h:7,
                    from arch/x86/um/../kernel/sys_ia32.c:49:
>> arch/x86/include/asm/vdso/processor.h:11:29: error: redefinition of 'rep_nop'
    static __always_inline void rep_nop(void)
                                ^~~~~~~
   In file included from include/linux/rcupdate.h:30:0,
                    from include/linux/rculist.h:11,
                    from include/linux/pid.h:5,
                    from include/linux/sched.h:14,
                    from arch/x86/um/../kernel/sys_ia32.c:25:
   arch/x86/um/asm/processor.h:24:20: note: previous definition of 'rep_nop' was here
    static inline void rep_nop(void)
                       ^~~~~~~
   In file included from include/vdso/processor.h:10:0,
                    from include/vdso/datapage.h:17,
                    from arch/x86/include/asm/vgtod.h:7,
                    from arch/x86/um/../kernel/sys_ia32.c:49:
>> arch/x86/include/asm/vdso/processor.h:16:43: error: macro "cpu_relax" passed 1 arguments, but takes just 0
    static __always_inline void cpu_relax(void)
                                              ^
>> arch/x86/include/asm/vdso/processor.h:17:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
    {
    ^
   In file included from arch/x86/include/asm/mshyperv.h:9:0,
                    from include/clocksource/hyperv_timer.h:18,
                    from arch/x86/include/asm/vdso/gettimeofday.h:21,
                    from include/vdso/datapage.h:126,
                    from arch/x86/include/asm/vgtod.h:7,
                    from arch/x86/um/../kernel/sys_ia32.c:49:
   arch/x86/include/asm/nospec-branch.h: In function 'mds_clear_cpu_buffers':
>> arch/x86/include/asm/nospec-branch.h:324:24: error: '__KERNEL_DS' undeclared (first use in this function); did you mean 'KERNEL_DS'?
     static const u16 ds = __KERNEL_DS;
                           ^~~~~~~~~~~
                           KERNEL_DS
   arch/x86/include/asm/nospec-branch.h:324:24: note: each undeclared identifier is reported only once for each function it appears in
   In file included from include/linux/kernel.h:11:0,
                    from arch/x86/um/../kernel/sys_ia32.c:24:
   arch/x86/include/asm/vdso/gettimeofday.h: In function '__arch_get_hw_counter':
>> arch/x86/include/asm/vdso/gettimeofday.h:246:27: error: 'VDSO_CLOCKMODE_TSC' undeclared (first use in this function); did you mean 'VDSO_CLOCKMODE_MAX'?
     if (likely(clock_mode == VDSO_CLOCKMODE_TSC))
                              ^
   include/linux/compiler.h:77:40: note: in definition of macro 'likely'
    # define likely(x) __builtin_expect(!!(x), 1)
                                           ^

vim +/rep_nop +11 arch/x86/include/asm/vdso/processor.h

abc22418db02b9 Vincenzo Frascino 2020-03-20   9  
abc22418db02b9 Vincenzo Frascino 2020-03-20  10  /* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
abc22418db02b9 Vincenzo Frascino 2020-03-20 @11  static __always_inline void rep_nop(void)
abc22418db02b9 Vincenzo Frascino 2020-03-20  12  {
abc22418db02b9 Vincenzo Frascino 2020-03-20  13  	asm volatile("rep; nop" ::: "memory");
abc22418db02b9 Vincenzo Frascino 2020-03-20  14  }
abc22418db02b9 Vincenzo Frascino 2020-03-20  15  
abc22418db02b9 Vincenzo Frascino 2020-03-20 @16  static __always_inline void cpu_relax(void)
abc22418db02b9 Vincenzo Frascino 2020-03-20 @17  {
abc22418db02b9 Vincenzo Frascino 2020-03-20  18  	rep_nop();
abc22418db02b9 Vincenzo Frascino 2020-03-20  19  }
abc22418db02b9 Vincenzo Frascino 2020-03-20  20  

:::::: The code at line 11 was first introduced by commit
:::::: abc22418db02b986fc5623c035507b6357e191ed x86/vdso: Enable x86 to use common headers

:::::: TO: Vincenzo Frascino <vincenzo.frascino@arm.com>
:::::: CC: Thomas Gleixner <tglx@linutronix.de>

---
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