compiler, clang: always inline when CONFIG_OPTIMIZE_INLINING is disabled (9a04dbcf) · Commits · 戴 / test

The motivation for commit ("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.google.com Signed-off-by:

David Rientjes <rientjes@google.com> Reported-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>

include/linux/compiler-clang.h

+0 −8

Original line number	Diff line number	Diff line
		@@ -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

include/linux/compiler-gcc.h

+11 −7

Original line number	Diff line number	Diff line
		@@ -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))

Admin message