The future of 32-bit Linux [LWN.net]

The future of 32-bit Linux

Posted Dec 6, 2020 14:37 UTC (Sun) by linusw (subscriber, #40300)
In reply to: The future of 32-bit Linux by anton
Parent article: The future of 32-bit Linux

This is a good point. There are some niche products, in a lecture on maintaining legacy ARM32 systems I pointed out that I am spending a considerable amount of time making sure that the Intel StrongARM-descendant IXP4xx is well supported. This is most famous because of its use in the NSLU2 and may seem legacy in some sense.

What is unique about the IXP4xx is the strictly military operating conditions:

* Temperature: -40°C to +85°C
* Humidity (non-condensing): 20% to 90%
* MTBF (mean time before failure): 60 Years at 55°C

This makes it plausible that this chip is in use in some installations that will outlive us all. I don't know of any ARM32 or ARM64 SoC with this kind of characteristics. If there is one, it will likely be as important as IXP4xx.

This doesn't mean it will have kernel upgrades though: it is more likely to be embedded and deployed in a remote location for decades. Sadly, it is probably network connected, so it would be better if it did see kernel upgrades.

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The future of 32-bit Linux

Posted Jan 1, 2021 11:03 UTC (Fri) by wtarreau (subscriber, #51152) [Link]

Only having kernel upgrades is not sufficient to keep an old system up to date. With newer kernels come new constraints and code sizes that are not always compatible with older hardware. I haven't tried booting 5.10 on my NSLU2 but I doubt it would be an option anymore. I barely managed to do it on a 9G20 board with 32MB RAM where I had to load it from the network to RAM because it wouldn't fit into the previous flash partition anymore.

The real problem with upgrades is connected systems. When you see a CNC device driven by an old 386 PC running MS-DOS 5.0 you smile and figure it was reliable and doesn't present any issue since that's not remotely accessible. It's the same for lots of deeply embedded Linux devices. The problem is that Linux is often used in networked environments and that it's so easy to connect it to a network that it's often done. And being exposed to the outside world *is* what requires security upgrades.

Thus we should admit that support for deeply buried systems can be dropped from newer kernels simply because these ones will not be updated and do not even need to. My point of view is that kernel support needs only to start from old devices that users want to repurpose. For sure I would be sad if I can't boot my old dockstar (ARM926) on a recent kernel. But let's be honest, the most recent version I've built for it was 3.7, 8 years ago. If 5.10 were to become the last one supported on it, it would apparently not be dramatic as I didn't feel the need for a more recent kernel on it for 8 years.