lockref: use cmpxchg64 explicitly for lockless updates
authorWill Deacon <will.deacon@arm.com>
Thu, 19 Sep 2013 18:06:46 +0000 (19:06 +0100)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 20 Sep 2013 16:04:28 +0000 (11:04 -0500)
commit8f4c344696b9f9f8471d7f342076ef10ed7f66a5
tree5266f6e86c81f6694f75e77c84c64a55123b04b1
parentdcb30e659287a6b40dafed1362532da42ec27229
lockref: use cmpxchg64 explicitly for lockless updates

The cmpxchg() function tends not to support 64-bit arguments on 32-bit
architectures.  This could be either due to use of unsigned long
arguments (like on ARM) or lack of instruction support (cmpxchgq on
x86).  However, these architectures may implement a specific cmpxchg64()
function to provide 64-bit cmpxchg support instead.

Since the lockref code requires a 64-bit cmpxchg and relies on the
architecture selecting ARCH_USE_CMPXCHG_LOCKREF, move to using cmpxchg64
instead of cmpxchg and allow 32-bit architectures to make use of the
lockless lockref implementation.

Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/lockref.c