save_and_disable_irqs does not need to use mov + msr (which was
introduced to work around a documentation bug which was propagated
into binutils.)  Use msr with an immediate constant, and if we're
building for ARMv6 or later, use the new CPSID instruction.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

The 'K' extension adds several new instructions to the ARMv6 ISA
which are primerily useful for SMP.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

We sometimes forgot to check whether the exclusive store succeeded.
Ensure that we always check.  Also ensure that we always use the
out of line versions, since the inline versions are not SMP safe.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

If we found that the bit was already in the desired state, we
would skip performing the operation, and write random data back.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NRussell King <rmk@arm.linux.org.uk>