On 02/11/2016 10:16 AM, Peter Zijlstra wrote: > On Thu, Feb 11, 2016 at 12:33:30AM +0100, Alfredo Alvarez Fernandez wrote: >> From: Alfredo Alvarez Fernandez <[email protected]> >> >> This was added to the kernel code in 1658d35ead5d ("list: Use >> READ_ONCE() when testing for empty lists") >> There's nothing special we need to do about it in userspace. >> >> Signed-off-by: Alfredo Alvarez Fernandez <[email protected]> >> --- >> tools/lib/lockdep/uinclude/linux/compiler.h | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/tools/lib/lockdep/uinclude/linux/compiler.h >> b/tools/lib/lockdep/uinclude/linux/compiler.h >> index 6386dc3..fd3e56a 100644 >> --- a/tools/lib/lockdep/uinclude/linux/compiler.h >> +++ b/tools/lib/lockdep/uinclude/linux/compiler.h >> @@ -3,6 +3,7 @@ >> >> #define __used __attribute__((__unused__)) >> #define unlikely >> +#define READ_ONCE(x) (x) >> #define WRITE_ONCE(x, val) x=(val) > > I would argue we'd still very much want the volatile cast for both READ > and WRITE_ONCE(). > > Why do these things have different semantics between user and kernel > space?
You're right. I'll send a patch. Thanks, Sasha
