tree 69ba3b450a769fa4a613a1f8c4e6454cdcfae5aa
parent 290815710b51de23f9ed6799d3e0bb762d4f907c
author Russell King <rmk@dyn-67.arm.linux.org.uk> 1243281480 +0100
committer Russell King <rmk+kernel@arm.linux.org.uk> 1243535967 +0100

[ARM] barriers: improve xchg, bitops and atomic SMP barriers

Mathieu Desnoyers pointed out that the ARM barriers were lacking:

- cmpxchg, xchg and atomic add return need memory barriers on
  architectures which can reorder the relative order in which memory
  read/writes can be seen between CPUs, which seems to include recent
  ARM architectures. Those barriers are currently missing on ARM.

- test_and_xxx_bit were missing SMP barriers.

So put these barriers in.  Provide separate atomic_add/atomic_sub
operations which do not require barriers.

Reported-Reviewed-and-Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>