4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Rientjes rientjes@google.com
commit 9a04dbcfb33b4012d0ce8c0282f1e3ca694675b1 upstream.
The motivation for commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions") was to suppress clang's warnings about unused static inline functions.
For configs without CONFIG_OPTIMIZE_INLINING enabled, such as any non-x86 architecture, `inline' in the kernel implies that __attribute__((always_inline)) is used.
Some code depends on that behavior, see https://lkml.org/lkml/2017/6/13/918:
net/built-in.o: In function `__xchg_mb': arch/arm64/include/asm/cmpxchg.h:99: undefined reference to `__compiletime_assert_99' arch/arm64/include/asm/cmpxchg.h:99: undefined reference to `__compiletime_assert_99
The full fix would be to identify these breakages and annotate the functions with __always_inline instead of `inline'. But since we are late in the 4.12-rc cycle, simply carry forward the forced inlining behavior and work toward moving arm64, and other architectures, toward CONFIG_OPTIMIZE_INLINING behavior.
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1706261552200.1075@chino.kir.corp.g... Signed-off-by: David Rientjes rientjes@google.com Reported-by: Sodagudi Prasad psodagud@codeaurora.org Tested-by: Sodagudi Prasad psodagud@codeaurora.org Tested-by: Matthias Kaehlcke mka@chromium.org Cc: Mark Rutland mark.rutland@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/compiler-clang.h | 8 -------- include/linux/compiler-gcc.h | 18 +++++++++++------- 2 files changed, 11 insertions(+), 15 deletions(-)
--- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -15,11 +15,3 @@ * with any version that can compile the kernel */ #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) - -/* - * GCC does not warn about unused static inline functions for - * -Wunused-function. This turns out to avoid the need for complex #ifdef - * directives. Suppress the warning in clang as well. - */ -#undef inline -#define inline inline __attribute__((unused)) notrace --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -66,18 +66,22 @@
/* * Force always-inline if the user requests it so via the .config, - * or if gcc is too old: + * or if gcc is too old. + * GCC does not warn about unused static inline functions for + * -Wunused-function. This turns out to avoid the need for complex #ifdef + * directives. Suppress the warning in clang as well by using "unused" + * function attribute, which is redundant but not harmful for gcc. */ #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) -#define inline inline __attribute__((always_inline)) notrace -#define __inline__ __inline__ __attribute__((always_inline)) notrace -#define __inline __inline __attribute__((always_inline)) notrace +#define inline inline __attribute__((always_inline,unused)) notrace +#define __inline__ __inline__ __attribute__((always_inline,unused)) notrace +#define __inline __inline __attribute__((always_inline,unused)) notrace #else /* A lot of inline functions can cause havoc with function tracing */ -#define inline inline notrace -#define __inline__ __inline__ notrace -#define __inline __inline notrace +#define inline inline __attribute__((unused)) notrace +#define __inline__ __inline__ __attribute__((unused)) notrace +#define __inline __inline __attribute__((unused)) notrace #endif
#define __always_inline inline __attribute__((always_inline))