On Fri, Jan 10, 2020 at 5:56 PM Will Deacon <will@xxxxxxxxxx> wrote: > > Prior to version 4.8, GCC may miscompile READ_ONCE() by erroneously > discarding the 'volatile' qualifier: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 > > We've been working around this using some nasty hacks which make > READ_ONCE() both horribly complicated and also prevent us from enforcing > that it is only used on scalar types. Since GCC 4.8 is pretty old for > kernel builds now, emit a warning if we detect it during the build. No objection to recommending gcc-4.8, but I think this should either just warn once during the kernel build instead of for every file, or it should become a hard requirement. Arnd
