On Sat, Aug 22, 2020 at 08:17:32PM +0200, Miguel Ojeda wrote: > On Sat, Aug 22, 2020 at 11:52 AM Sedat Dilek <sedat.di...@gmail.com> wrote: > > > > I am asking myself who is using such ancient compilers? > > There are many users/companies using older versions of compilers, > kernels and everything. GCC <= 4.9 will still be used/supported (by > third parties) for a handful of years at least. > > However, the important question is whether those users/companies care > about running the latest kernels. Many of those definitely do not want > to touch their kernel either. For those that do, there are several > longterms to pick from that still support 4.9, as well as other > workarounds. > > Thus I am usually in favor of raising the minimum whenever new hacks > are required to be added. On the other hand, we already raised the > version twice this year and it is not clear to me what is the minimum > version we would need to go for to ensure this does not bite us. > > > If this is a real problem with GCC version <= 5, so can this be moved > > to a GCC specific include header-file? > > Thinking of include/linux/compiler-gcc.h or > > include/linux/compiler_types.h with a GCC-VERSION check? > > That would be better if it can be done, yes. > > Cheers, > Miguel
The fix landed in gcc 6.5, 7.3 and 8.1. The bug is presumably quite difficult to actually trigger. As a sample data point, I verified that 7.1 vs 7.1+fix have no differences on 32-bit and 64-bit x86 defconfigs, on current mainline. Assuming we don't want to risk removing force_order, I'd suggest - make it an input/output operand, so it enforces ordering fully. - either restrict it to gcc < 8, or just provide a proper definition in some file (maybe arch/x86/kernel/cpu/common.c)? Thanks.
