| Message ID | alpine.DEB.2.10.1706261552200.1075@chino.kir.corp.google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2017-06-26 16:03, David Rientjes wrote: > The motivation of commit abb2ea7dfd82 ("compiler, clang: suppress > warning > for unused static inline functions") is 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. > > Reported-by: Sodagudi Prasad <psodagud@codeaurora.org> > Tested-by: Matthias Kaehlcke <mka@chromium.org> > Signed-off-by: David Rientjes <rientjes@google.com> > --- > Resend of http://marc.info/?l=linux-kernel&m=149681501816319 for 4.12 > inclusion. > > Prasad, please add your Tested-by. > I have compile tested this change with clang, please add - Tested-by: Sodagudi Prasad <psodagud@codeaurora.org> -Thanks, Prasad > include/linux/compiler-clang.h | 8 -------- > include/linux/compiler-gcc.h | 18 +++++++++++------- > 2 files changed, 11 insertions(+), 15 deletions(-) > > diff --git a/include/linux/compiler-clang.h > b/include/linux/compiler-clang.h > --- 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 > diff --git a/include/linux/compiler-gcc.h > b/include/linux/compiler-gcc.h > --- 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))
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h --- 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 diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h --- 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))
The motivation of commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions") is 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. Reported-by: Sodagudi Prasad <psodagud@codeaurora.org> Tested-by: Matthias Kaehlcke <mka@chromium.org> Signed-off-by: David Rientjes <rientjes@google.com> --- Resend of http://marc.info/?l=linux-kernel&m=149681501816319 for 4.12 inclusion. Prasad, please add your Tested-by. include/linux/compiler-clang.h | 8 -------- include/linux/compiler-gcc.h | 18 +++++++++++------- 2 files changed, 11 insertions(+), 15 deletions(-)