arm64: fix unreachable code issue with cmpxchg

[ Upstream commit 920fdab7b3ce98c14c840261e364f490f3679a62 ]

On arm64 build with clang, sometimes the __cmpxchg_mb is not inlined
when CONFIG_OPTIMIZE_INLINING is set.
Clang then fails a compile-time assertion, because it cannot tell at
compile time what the size of the argument is:

mm/memcontrol.o: In function `__cmpxchg_mb':
memcontrol.c:(.text+0x1a4c): undefined reference to `__compiletime_assert_175'
memcontrol.c:(.text+0x1a4c): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `__compiletime_assert_175'

Mark all of the cmpxchg() style functions as __always_inline to
ensure that the compiler can see the result.

Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/648
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Tested-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index 0f2e1ab5e16669d3cc7dd27170243f5f79424a6b..9b2e2e2e728ae7abaf7252ea02337654549751e2 100644 (file)
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -73,7 +73,7 @@ __XCHG_CASE( ,  ,  mb_8, dmb ish, nop,  , a, l, "memory")
 #undef __XCHG_CASE
 
 #define __XCHG_GEN(sfx)                                                        \
-static inline unsigned long __xchg##sfx(unsigned long x,               \
+static __always_inline  unsigned long __xchg##sfx(unsigned long x,     \
                                        volatile void *ptr,             \
                                        int size)                       \
 {                                                                      \
@@ -115,7 +115,7 @@ __XCHG_GEN(_mb)
 #define xchg(...)              __xchg_wrapper( _mb, __VA_ARGS__)
 
 #define __CMPXCHG_GEN(sfx)                                             \
-static inline unsigned long __cmpxchg##sfx(volatile void *ptr,         \
+static __always_inline unsigned long __cmpxchg##sfx(volatile void *ptr,        \
                                           unsigned long old,           \
                                           unsigned long new,           \
                                           int size)                    \
@@ -248,7 +248,7 @@ __CMPWAIT_CASE( ,  , 8);
 #undef __CMPWAIT_CASE
 
 #define __CMPWAIT_GEN(sfx)                                             \
-static inline void __cmpwait##sfx(volatile void *ptr,                  \
+static __always_inline void __cmpwait##sfx(volatile void *ptr,         \
                                  unsigned long val,                    \
                                  int size)                             \
 {                                                                      \