On Wed, 13 Jan 2021 at 23:09, Linus Torvalds <torva...@linux-foundation.org> wrote: > > On Wed, Jan 13, 2021 at 1:44 PM Russell King - ARM Linux admin > <li...@armlinux.org.uk> wrote: > > > > So, maybe the Sparc issue was just a similar but different bug in gcc > > 4.9.x. > > Good catch. And I know this bug has happened independently on > different architectures several times (I remember this on x86-64 as > well), so I started looking around. > > And in fact, 4.9 was buggy on x86-64 too: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61904 > > And yeah, _that_ gcc bug wasn't actually x86-64 specific, but > apparently a generic instruction scheduling bug. > > So it's an independent bug, but I do have to admit that the arguments > against 4.9 are piling up (even if that particular fix apparently got > fixed in the gcc branches and apparently backported to distro > compilers too). >
So if the arguments are piling up, what is holding us back, other than inertia? RHEL 7 used to be a factor, but it ships with 4.8 not 4.9, so its users already need to upgrade. Is anyone aware of a good reason to keep 4.9 supported? Are any other long term supported distros using 4.9.x? I know that distros probably backported fixes for all of these issues, but without a way to interrogate the compiler about this, that doesn't really make a difference IMHO. Note that banning 4.9 for arm64 and banning it in general should be two different changes in any case, as the former will need to be backported to -stable kernels as well. -- Ard.