tree fdd16d5585a986cf8cbed140f533d08d152bbc4f
parent 4314895165623879937f46d767673654662b570c
author Peter Zijlstra <peterz@infradead.org> 1378905564 +0200
committer Ingo Molnar <mingo@kernel.org> 1380109988 +0200

x86: Use asm goto to implement better modify_and_test() functions

Linus suggested using asm goto to get rid of the typical SETcc + TEST
instruction pair -- which also clobbers an extra register -- for our
typical modify_and_test() functions.

Because asm goto doesn't allow output fields it has to include an
unconditinal memory clobber when it changes a memory variable to force
a reload.

Luckily all atomic ops already imply a compiler barrier to go along
with their memory barrier semantics.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-0mtn9siwbeo1d33bap1422se@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>