Commit 9a04dbcf authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

compiler, clang: always inline when CONFIG_OPTIMIZE_INLINING is disabled

The motivation for commit abb2ea7d ("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: default avatarDavid Rientjes <rientjes@google.com>
Reported-by: default avatarSodagudi Prasad <psodagud@codeaurora.org>
Tested-by: default avatarSodagudi Prasad <psodagud@codeaurora.org>
Tested-by: default avatarMatthias 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9ced560b
......@@ -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
......@@ -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))
......
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