On Fri, Oct 03, 2014 at 05:41:34PM +0200, Michal Hocko wrote: > On Fri 03-10-14 19:36:23, Vladimir Davydov wrote: > > On Thu, Oct 02, 2014 at 08:07:48AM -0400, Johannes Weiner wrote: > [...] > > > The barriers are implied in change-return atomics, which is why there > > > is an xchg. But it's clear that this needs to be documented. This?: > > > > With the comments it looks correct to me, but I wonder if we can always > > rely on implicit memory barriers issued by atomic ops. Are there any > > archs where it doesn't hold? > > xchg is explcitly mentioned in Documentation/memory-barriers.txt so it > is expected to be barrier on all archs. Besides that not all atomic ops > imply memory barriers. Only those that "modifies some state in memory > and returns information about the state" do. Thank you for the info, now it's clear to me. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>