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SubjectRe: [PATCHv4 0/9] ACCESS_ONCE and non-scalar accesses
Am 03.12.2014 um 23:30 schrieb Christian Borntraeger:
> As discussed on LKML http://marc.info/?i=54611D86.4040306%40de.ibm.com
> ACCESS_ONCE might fail with specific compiler for non-scalar accesses.
>
> Here is a set of patches to tackle that problem.
>
> The first patch introduce READ_ONCE and ASSIGN_ONCE. If the data structure
> is larger than the machine word size memcpy is used and a warning is emitted.
> The next patches fix up all in-tree users of ACCESS_ONCE on non-scalar types.
> The last patch forces ACCESS_ONCE to work only on scalar types.
>
> I have cross-compiled the resulting kernel with defconfig and gcc 4.9 for
> microblaze, m68k, alpha, s390,x86_64, i686, sparc, sparc64, mips,
> ia64, arm and arm64.
>
> Runtime tested on s390x and x86_64. I have also verified that ASSIGN_ONCE works
> as expected with some test changes as there are no user in this patch series.
>
> Linus, ok for the next merge window?
>
> Christian Borntraeger (9):
> kernel: Provide READ_ONCE and ASSIGN_ONCE
> mm: replace ACCESS_ONCE with READ_ONCE or barriers
> x86/spinlock: Replace ACCESS_ONCE with READ_ONCE
> x86/gup: Replace ACCESS_ONCE with READ_ONCE
> mips/gup: Replace ACCESS_ONCE with READ_ONCE
> arm64/spinlock: Replace ACCESS_ONCE READ_ONCE
> arm/spinlock: Replace ACCESS_ONCE with READ_ONCE
> s390/kvm: REPLACE ACCESS_ONCE with READ_ONCE
> kernel: tighten rules for ACCESS ONCE
>
> arch/arm/include/asm/spinlock.h | 4 +--
> arch/arm64/include/asm/spinlock.h | 4 +--
> arch/mips/mm/gup.c | 2 +-
> arch/s390/kvm/gaccess.c | 14 ++++----
> arch/x86/include/asm/spinlock.h | 8 ++---
> arch/x86/mm/gup.c | 2 +-
> include/linux/compiler.h | 74 ++++++++++++++++++++++++++++++++++++++-
> mm/gup.c | 2 +-
> mm/memory.c | 2 +-
> mm/rmap.c | 3 +-
> 10 files changed, 95 insertions(+), 20 deletions(-)
>

FWIW, the code is on

git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux.git linux-next
and
git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux.git ACCESS_ONCE

I rebased the queue against rc3 + the initial patch that triggered the whole discussion.

Christian



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