Hi Dmitry, hi Ingo, since commit 8bf705d13039 ("locking/atomic/x86: Switch atomic.h to use atomic-instrumented.h") on linux-next (tested and bisected from tag next-20180316), compiling the kernel with clang fails with: In file included from arch/x86/entry/vdso/vdso32/vclock_gettime.c:33: In file included from arch/x86/entry/vdso/vdso32/../vclock_gettime.c:15: In file included from ./arch/x86/include/asm/vgtod.h:6: In file included from ./include/linux/clocksource.h:13: In file included from ./include/linux/timex.h:56: In file included from ./include/uapi/linux/timex.h:56: In file included from ./include/linux/time.h:6: In file included from ./include/linux/seqlock.h:36: In file included from ./include/linux/spinlock.h:51: In file included from ./include/linux/preempt.h:81: In file included from ./arch/x86/include/asm/preempt.h:7: In file included from ./include/linux/thread_info.h:38: In file included from ./arch/x86/include/asm/thread_info.h:53: In file included from ./arch/x86/include/asm/cpufeature.h:5: In file included from ./arch/x86/include/asm/processor.h:21: In file included from ./arch/x86/include/asm/msr.h:67: In file included from ./arch/x86/include/asm/atomic.h:279: ./include/asm-generic/atomic-instrumented.h:295:10: error: invalid output size for constraint '=a' return arch_cmpxchg((u64 *)ptr, (u64)old, (u64)new); ^ ./arch/x86/include/asm/cmpxchg.h:149:2: note: expanded from macro 'arch_cmpxchg' __cmpxchg(ptr, old, new, sizeof(*(ptr))) ^ ./arch/x86/include/asm/cmpxchg.h:134:2: note: expanded from macro '__cmpxchg' __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX) ^ ./arch/x86/include/asm/cmpxchg.h:95:17: note: expanded from macro '__raw_cmpxchg' : "=a" (__ret), "+m" (*__ptr) \ ^ (... and some more similar and closely related errors) Best regards, Lukas