On Tue, Oct 24, 2017 at 11:25:12AM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> > From: Will Deacon <will.deacon@xxxxxxx>
> >
> > linux/compiler.h is included indirectly by linux/types.h via
> > uapi/linux/types.h -> uapi/linux/posix_types.h -> linux/stddef.h
> > -> uapi/linux/stddef.h and is needed to provide a proper definition of
> > offsetof.
> >
> > Unfortunately, compiler.h requires a definition of
> > smp_read_barrier_depends() for defining lockless_dereference and soon
> > for defining READ_ONCE, which means that all
> > users of READ_ONCE will need to include asm/barrier.h to avoid splats
> > such as:
> >
> > In file included from include/uapi/linux/stddef.h:1:0,
> > from include/linux/stddef.h:4,
> > from arch/h8300/kernel/asm-offsets.c:11:
> > include/linux/list.h: In function 'list_empty':
> > >> include/linux/compiler.h:343:2: error: implicit declaration of function 'smp_read_barrier_depends' [-Werror=implicit-function-declaration]
> > smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
> > ^
> >
> > A better alternative is to include asm/barrier.h in linux/compiler.h,
> > but this requires a type definition for "bool" on some architectures
> > (e.g. x86), which is defined later by linux/types.h. Type "bool" is also
> > used directly in linux/compiler.h, so the whole thing is pretty fragile.
> >
> > This patch splits compiler.h in two: compiler-types.h contains type
> > annotations, definitions and the compiler-specific parts, whereas
> > compiler.h #includes compiler-types.h and additionally defines macros
> > such as {READ,WRITE.ACCESS}_ONCE.
> >
> > uapi/linux/stddef.h and linux/linkage.h are then moved over to include
> > linux/compiler-types.h, which fixes the build for h8 and blackfin.
> >
> > Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> > Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> > [ paulmck: Add Will's fixes for issues reported by kbuild test robot. ]
> > ---
> > arch/arm/include/asm/ptrace.h | 3 +-
> > arch/sparc/include/asm/ptrace.h | 1 +
> > arch/um/include/shared/init.h | 2 +-
> > include/linux/compiler-clang.h | 2 +-
> > include/linux/compiler-gcc.h | 2 +-
> > include/linux/compiler-intel.h | 2 +-
> > include/linux/compiler-types.h | 274 ++++++++++++++++++++++++++++++++++++++++
> > include/linux/compiler.h | 265 +-------------------------------------
>
> The common pattern is to use an underscore (compiler_types.h), not a hyphen
> (compiler-types.h) ...
I just followed the existing examples of compiler-{clang,gcc,intel}.h!
I can respin if you like, but it will be inconsistent with the existing
compiler* headers and it's not like there aren't other hyphenated header
files in include/linux/ (I count 433).
Will
