On Sat, Aug 27, 2022 at 01:47:48AM +0200, Peter Zijlstra wrote: > On Fri, Aug 26, 2022 at 01:10:39PM -0400, Alan Stern wrote: > > > > - some babbling about a missing propagation -- ISTR Linux if stuffed > > > full of them, specifically we require stores to auto propagate > > > without help from barriers > > > > Not a missing propagation; a late one. > > > > Don't understand what you mean by "auto propagate without help from > > barriers". > > Linux hard relies on: > > CPU0 CPU1 > > WRITE_ONCE(foo, 1); while (!READ_ONCE(foo)); > > making forward progress. Indeed yes. As far as I can tell, this requirement is not explicitly mentioned in the LKMM, although it certainly is implicit. I can't even think of a way to express it in a form Herd could verify. > There were a few 'funny' uarchs that were broken, see for example commit > a30718868915f. Ha! That commit should be a lesson in something, although I'm not sure what. :-) Alan
