This is a note to let you know that I've just added the patch titled powerpc/barrier: Avoid collision with clang's __lwsync macro to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-barrier-avoid-collision-with-clang-s-__lwsync-macro.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 015d98149b326e0f1f02e44413112ca8b4330543 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor <nathan@xxxxxxxxxx> Date: Fri, 28 May 2021 11:27:52 -0700 Subject: powerpc/barrier: Avoid collision with clang's __lwsync macro From: Nathan Chancellor <nathan@xxxxxxxxxx> commit 015d98149b326e0f1f02e44413112ca8b4330543 upstream. A change in clang 13 results in the __lwsync macro being defined as __builtin_ppc_lwsync, which emits 'lwsync' or 'msync' depending on what the target supports. This breaks the build because of -Werror in arch/powerpc, along with thousands of warnings: In file included from arch/powerpc/kernel/pmc.c:12: In file included from include/linux/bug.h:5: In file included from arch/powerpc/include/asm/bug.h:109: In file included from include/asm-generic/bug.h:20: In file included from include/linux/kernel.h:12: In file included from include/linux/bitops.h:32: In file included from arch/powerpc/include/asm/bitops.h:62: arch/powerpc/include/asm/barrier.h:49:9: error: '__lwsync' macro redefined [-Werror,-Wmacro-redefined] #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") ^ <built-in>:308:9: note: previous definition is here #define __lwsync __builtin_ppc_lwsync ^ 1 error generated. Undefine this macro so that the runtime patching introduced by commit 2d1b2027626d ("powerpc: Fixup lwsync at runtime") continues to work properly with clang and the build no longer breaks. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://github.com/ClangBuiltLinux/linux/issues/1386 Link: https://github.com/llvm/llvm-project/commit/62b5df7fe2b3fda1772befeda15598fbef96a614 Link: https://lore.kernel.org/r/20210528182752.1852002-1-nathan@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/include/asm/barrier.h | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h @@ -44,6 +44,8 @@ # define SMPWMB eieio #endif +/* clang defines this macro for a builtin, which will not work with runtime patching */ +#undef __lwsync #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") #define dma_rmb() __lwsync() #define dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory") Patches currently in stable-queue which might be from nathan@xxxxxxxxxx are queue-5.4/powerpc-barrier-avoid-collision-with-clang-s-__lwsync-macro.patch