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    Subject[PATCH v2 00/10] Rework READ_ONCE() to improve codegen
    Date
    Hi folks,

    This is version two of the patches I previously posted as an RFC here:

    https://lore.kernel.org/lkml/20200110165636.28035-1-will@kernel.org

    Changes since then include:

    * Adopted a less vomit-inducing series of macros for __unqual_scalar_typeof

    * Cast to 'const' in READ_ONCE() to prevent assignment to the resulting
    expression

    * Only warn once at build-time if GCC prior to 4.8 is detected...

    * ... and then raise the minimum GCC version to 4.8, with an error for
    older versions of the compiler

    * Remove some dead gcov code so that the resulting diffstat can distract
    from those less vomit-inducing macros I mentioned earlier on

    Failing the build for older compilers is always a contentious topic, so
    I've done that as a separate couple of patches on the end in case we end
    up dropping or reverting them.

    Cheers,

    Will

    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Segher Boessenkool <segher@kernel.crashing.org>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
    Cc: Masahiro Yamada <masahiroy@kernel.org>
    Cc: Nick Desaulniers <ndesaulniers@google.com>

    --->8

    Will Deacon (10):
    compiler/gcc: Emit build-time warning for GCC prior to version 4.8
    netfilter: Avoid assigning 'const' pointer to non-const pointer
    fault_inject: Don't rely on "return value" from WRITE_ONCE()
    READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE()
    READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses
    READ_ONCE: Drop pointer qualifiers when reading from scalar types
    locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros
    arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release
    macros
    compiler/gcc: Raise minimum GCC version for kernel builds to 4.8
    gcov: Remove old GCC 3.4 support

    Documentation/process/changes.rst | 2 +-
    arch/arm/crypto/Kconfig | 12 +-
    arch/arm64/include/asm/barrier.h | 16 +-
    crypto/Kconfig | 1 -
    drivers/xen/time.c | 2 +-
    include/asm-generic/barrier.h | 16 +-
    include/linux/compiler-gcc.h | 5 +-
    include/linux/compiler.h | 129 +++----
    include/linux/compiler_types.h | 21 ++
    init/Kconfig | 5 +-
    kernel/gcov/Kconfig | 24 --
    kernel/gcov/Makefile | 3 +-
    kernel/gcov/gcc_3_4.c | 573 ------------------------------
    lib/fault-inject.c | 4 +-
    net/netfilter/core.c | 2 +-
    net/xdp/xsk_queue.h | 2 +-
    scripts/Kconfig.include | 3 +
    scripts/gcc-plugins/Kconfig | 4 +-
    18 files changed, 111 insertions(+), 713 deletions(-)
    delete mode 100644 kernel/gcov/gcc_3_4.c

    --
    2.25.0.341.g760bfbb309-goog

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