• Will Deacon's avatar
    linux/compiler.h: Split into compiler.h and compiler_types.h · d1515582
    Will Deacon authored
    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
    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.
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1508840570-22169-2-git-send-email-will.deacon@arm.com
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>