[PATCH/RFC 0/7] ACCESS_ONCE and non-scalar accesses

[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
is already in kvm/next).
The last patch will force ACCESS_ONCE to error-out if it is used
on non-scalar accesses.
I have cross-compiled the resulting kernel with defconfig for
microblaze, m68k, alpha, s390,x86_64, i686, sparc, sparc64, mips,
ia64, arm and arm64.

So hopefully this patch set should be complete regarding the non-scalar
accesses. (As Linus pointed out, accesses > word size are a problem
on its own, but this patch set does not tackle this)

The result is also available as 0d199efcfc9875b8de17bb4fe1d87a27bd39a172
on
git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux.git ACCESS_ONCE

Now:
- It would be good to have the changes reviewed by component experts.
- It would also be good if architecture maintainers could double check, that
  "kernel: Force ACCESS_ONCE to work only on scalar types" does not break
  anything beyond defconfig.
- some comments about cc stable

Thanks

Christian
----------------------------------------------------------------
Christian Borntraeger (7):
      KVM: s390: Fix ipte locking
      mm: replace page table access via ACCESS_ONCE with barriers
      x86: Rework ACCESS_ONCE for spinlock code
      x86: Replace ACCESS_ONCE in gup with a barrier
      mips: Replace ACCESS_ONCE in gup with a barrier
      arm64: Replace ACCESS_ONCE for spinlock code with barriers
      kernel: Force ACCESS_ONCE to work only on scalar types

 arch/arm64/include/asm/spinlock.h |  7 +++++--
 arch/mips/mm/gup.c                |  6 ++++--
 arch/s390/kvm/gaccess.c           | 20 ++++++++++++++------
 arch/x86/include/asm/spinlock.h   | 14 +++++++++-----
 arch/x86/mm/gup.c                 |  7 +++++--
 include/linux/compiler.h          | 12 +++++++++++-
 mm/gup.c                          |  4 +++-
 mm/memory.c                       |  3 ++-
 mm/rmap.c                         |  3 ++-
 9 files changed, 55 insertions(+), 21 deletions(-)

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