On Fri, Nov 22, 2024 at 09:45:52AM +0000, Lorenzo Stoakes wrote: > On Thu, Nov 21, 2024 at 11:22:58AM -0800, Guenter Roeck wrote: > > On Thu, Nov 21, 2024 at 11:08:54AM -0800, Guenter Roeck wrote: > > > On Thu, Nov 21, 2024 at 07:50:33PM +0100, Geert Uytterhoeven wrote: > > > > On Thu, Nov 21, 2024 at 7:30 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > > > > On Thu, Nov 21, 2024 at 09:23:28AM -0800, Christoph Lameter (Ampere) wrote: > > > > > > On Thu, 21 Nov 2024, Geert Uytterhoeven wrote: > > > > > > > Linux has supported m68k since last century. > > > > > > > > > > > > Yeah I fondly remember the 80s where 68K systems were always out of reach > > > > > > for me to have. The dream system that I never could get my hands on. The > > > > > > creme de la creme du jour. I just had to be content with the 6800 and > > > > > > 6502 processors. Then IBM started the sick road down the 8088, 8086 > > > > > > that led from crap to more crap. Sigh. > > > > > > > > > > > > > Any new such assumptions are fixed quickly (at least in the kernel). > > > > > > > If you need a specific alignment, make sure to use __aligned and/or > > > > > > > appropriate padding in structures. > > > > > > > And yes, the compiler knows, and provides __alignof__. > > > > > > > > > > > > > > > How do you deal with torn reads/writes in such a scenario? Is this UP > > > > > > > > only? > > > > > > > > > > > > > > Linux does not support (rate) SMP m68k machines. > > > > > > > > s/rate/rare/ > > > > > > > > > > Ah. Ok that explains it. > > > > > > > > > > > > Do we really need to maintain support for a platform that has been > > > > > > obsolete for decade and does not even support SMP? > > > > > > > > > > Since this keeps coming up, I think there is a much more important > > > > > question to ask: > > > > > > > > > > Do we really need to continue supporting nommu machines ? Is anyone > > > > > but me even boot testing those ? > > > > > > > > Not all m68k platform are nommu. > > > > > > > Yes, I wasn't trying to point to m68k, but to nommu in general. > > > > > > > For some more context: I think it is highly unlikely that anyone is really > > using a recent version of Linux on a nommu machine. Maybe that was the case > > 10 or 20 years ago, but nowadays there are other operating systems which are > > much better suited than Linux for such systems. Yet, there is a _lot_ of > > nommu code in the kernel. In comparison, supporting m68k (mmu based) is a no > > brainer, plus there are actually people like Geert actively supporting it. > > > > If we are talking about dropping m68k support, we should really talk about > > dropping nommu support first to get some _real_ benefit. > > > > Guenter > > > > > > I couldn't agree more re: nommu, it is the real source of maintenance > issues at least for us in mm, and one I've personally run into many times. > > An aside, but note that there is a proposal to add nommu support to UML, > which would entirely prevent our ability to eliminate it [0] (though it > would make testing it easier! :) > > [0]:https://lore.kernel.org/all/cover.1731290567.git.thehajime@xxxxxxxxx/ To update, some interesting discussion in this thread suggests that indeed, there is an ongoing need for nommu regardless [1]. In which case this nommu uml series is rather helpful for testing :) [1]:https://lore.kernel.org/linux-mm/09060fcf-47e4-424f-9ab7-ee2f7919dbf5@lucifer.local/T/#m0cb0ace28f3905182369790ddc1b494d408587b9
