linux-kernel - [PATCHv4 0/9] ACCESS_ONCE and non-scalar accesses

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Date:	Wed,  3 Dec 2014 23:30:12 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-arch@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
	torvalds@...ux-foundation.org,
	Christian Borntraeger <borntraeger@...ibm.com>
Subject: [PATCHv4 0/9] ACCESS_ONCE and non-scalar accesses

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(-)

-- 
1.9.3

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