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.

We first introduce READ_ONCE/ASSIGN_ONCE as suggested by Linus. These
wrappers will make all accesses via scalar wrappers and will also check
that accesses are <= the word size of the system.
The next changes will modify current users of ACCESS_ONCE on non-scalar
types to use READ_ONCE/ASSIGN_ONCE or barrier where necessary.
The 2nd to last patch will force ACCESS_ONCE to error-out if it is used
on non-scalar accesses.

The series is cross-compiled the resulting kernel with defconfig for
microblaze, m68k, alpha, s390,x86_64, i686, sparc, sparc64, mips,
ia64, arm and arm64.
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