x86: Add memory modify constraints to xchg() and cmpxchg()

xchg() and cmpxchg() modify their memory operands, not merely read
them.  For some versions of gcc the "memory" clobber has apparently
dealt with the situation, but not for all.

Originally-by: Linus Torvalds <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Cc: Glauber Costa <[email protected]>
Cc: Avi Kivity <[email protected]>
Cc: Peter Palfrader <[email protected]>
Cc: Greg KH <[email protected]>
Cc: Alan Cox <[email protected]>
Cc: Zachary Amsden <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: <[email protected]>
LKML-Reference: <[email protected]>

0 files changed, 0 insertions, 0 deletions