As discussed on LKML http://marc.info/?i=54611D86.4040306%40de.ibm.com ACCESS_ONCE might fail with specific compilers 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. Due to all the trouble when dealing with linux-next, I will defer the patch that forces ACCESS_ONCE to work only on scalar types after rc1 to give it a full spin in linux-next. If nobody complains I will ask Linus to pull this for 3.19 next week. The tree can be found at git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux.git linux-next Changelog: v4->v5: 1. READ_ONCE/ASSIGN_ONCE use x instead of p 2. linux/types.h --> uapi/linux/types.h u??-->__u?? to avoid header inclusion fun and compile errors 3. Actually provide data_access_exceeds_word_size. 4. also move handle_pte_fault to a barrier as there is ppc44x which has 64bit ptes and 32bit word size. Some sanity check from a VM person would be good. Cc: linux-mm@xxxxxxxxx Christian Borntraeger (8): 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 barrier fixup with READ_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 | 18 ++++------ arch/x86/include/asm/spinlock.h | 8 ++--- arch/x86/mm/gup.c | 2 +- include/linux/compiler.h | 70 +++++++++++++++++++++++++++++++++++++++ lib/Makefile | 2 +- lib/access.c | 8 +++++ mm/gup.c | 2 +- mm/memory.c | 11 +++++- mm/rmap.c | 3 +- 12 files changed, 108 insertions(+), 26 deletions(-) create mode 100644 lib/access.c -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>