Hi Andrew, It's probably a bug fix that unveils the link errors. tree: https://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git since-4.10 head: 7ef887134f52395c4883daddf957aa055578c215 commit: e8bbed4699bb09d2437998bce09c6d8aa20d5963 [522/528] x86-atomic-move-__atomic_add_unless-out-of-line-fix config: um-x86_64_defconfig (attached as .config) compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 reproduce: git checkout e8bbed4699bb09d2437998bce09c6d8aa20d5963 # save the attached .config to linux build tree make ARCH=um SUBARCH=x86_64 All errors (new ones prefixed by >>): kernel/built-in.o: In function `__atomic_add_unless': >> include/asm-generic/atomic-instrumented.h:70: undefined reference to `__arch_atomic_add_unless' >> include/asm-generic/atomic-instrumented.h:70: undefined reference to `__arch_atomic_add_unless' >> include/asm-generic/atomic-instrumented.h:70: undefined reference to `__arch_atomic_add_unless' >> include/asm-generic/atomic-instrumented.h:70: undefined reference to `__arch_atomic_add_unless' >> include/asm-generic/atomic-instrumented.h:70: undefined reference to `__arch_atomic_add_unless' kernel/built-in.o:include/asm-generic/atomic-instrumented.h:70: more undefined references to `__arch_atomic_add_unless' follow collect2: error: ld returned 1 exit status vim +70 include/asm-generic/atomic-instrumented.h 6a9463f1 Dmitry Vyukov 2017-03-15 64 return arch_atomic64_cmpxchg(v, old, new); 6a9463f1 Dmitry Vyukov 2017-03-15 65 } 6a9463f1 Dmitry Vyukov 2017-03-15 66 6a9463f1 Dmitry Vyukov 2017-03-15 67 static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u) 6a9463f1 Dmitry Vyukov 2017-03-15 68 { d6c79f35 Dmitry Vyukov 2017-03-15 69 kasan_check_write(v, sizeof(*v)); 6a9463f1 Dmitry Vyukov 2017-03-15 @70 return __arch_atomic_add_unless(v, a, u); 6a9463f1 Dmitry Vyukov 2017-03-15 71 } 6a9463f1 Dmitry Vyukov 2017-03-15 72 6a9463f1 Dmitry Vyukov 2017-03-15 73 :::::: The code at line 70 was first introduced by commit :::::: 6a9463f1bb9223614d0ca81a5b237102ce81c7c1 asm-generic, x86: wrap atomic operations :::::: TO: Dmitry Vyukov <dvyukov@xxxxxxxxxx> :::::: CC: Michal Hocko <mhocko@xxxxxxxx> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
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