PowerPC 601 Support Being Retired in Linux 5.10 – The First 32-Bit PowerPC CPU

Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by rwmj on Saturday October 10, 2020 @04:35PM (#24741698)

I wonder if anyone using Linux regularly ran it on a PPC 601?

Because as a former owner of an Itanium[1] I can say that even when a processor is "officially supported" upstream, unless a critical mass of people actually use it there are lots of weird regressions. Debian/ia64 at the time (2015) only partially worked - lots of common utilities would randomly segfault or fail in peculiar ways.

[1] https://rwmj.wordpress.com/2014/09/08/raise-the-itanic/ https://rwmj.wordpress.com/2015/05/03/raise-the-itanic-part-...

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by Narishma on Saturday October 10, 2020 @05:00PM (#24741864)

> unless a critical mass of people actually use it there are lots of weird regressions.

Even 32-bit x86 has been having some of those weird regressions these past few years.

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by pmarin on Sunday October 11, 2020 @06:58AM (#24744939)

Can you provide links to any of those weird regressions?

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by rwmj on Sunday October 11, 2020 @10:17AM (#24745948)

I don't have anything specific, but until Fedora stopped compiling a i686 kernel altogether a few years ago we had to disable our tests of "does the current kernel boot on qemu" for years on i686 because those kernels simply didn't work. And no one really cared. And no one cared again when Fedora dropped i686 (except for multilib on x86-64) entirely.

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by Scuds on Saturday October 10, 2020 @05:44PM (#24742093)

The kernel people can say one thing, userland people can say another.

"It compiles, it runs! No smoke tests. libc is busted? oh well, patches welcome!"

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by rbanffy on Saturday October 10, 2020 @06:30PM (#24742344)

I made the same comment above about the kernel. How covered by automated tests is glibc?

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by cbmuser on Saturday October 10, 2020 @06:29PM (#24742332)

> Debian/ia64 at the time (2015) only partially worked - lots of common utilities would randomly segfault or fail in peculiar ways.

It works reasonably well these days, albeit not perfect.

There are issues with kernels >= 4.15 on larger NUMA systems, but otherwise it runs mostly fine.

Images can be found here:

> https://cdimage.debian.org/cdimage/ports/

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by kjs3 on Saturday October 10, 2020 @07:28PM (#24742676)

Yeah...I tried to run 68k Linux for a while (quite some time ago, to be fair) and got to "Nope" pretty quick. Your 'critical mass' observation is absolutely spot on: Open Source is about the 'number of eyes on the code', and it turns out you clearly need a certain number of eyes for it to work in the long run.

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by rbanffy on Saturday October 10, 2020 @06:29PM (#24742330)

How covered by automated tests is the kernel? Some tests would require hardware emulators to some degree, but a lot wouldn't.

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Re:PowerPC 601 Support Being Retired in Linux 5.10 – The Fir... by rwmj on Sunday October 11, 2020 @10:11AM (#24745906)

Last time I submitted a kernel patch which added some new user-visible API:

  $ grep Umask /proc/self/status
  Umask: 0002

I had to also submit a test to go along with it. I understand that these are run by CI on the main architectures, although it didn't appear to be a condition of accepting the patch that the test was correct on all arches. Also I wonder if their CI really runs on PPC601 and IA64, I guess probably not. (Obviously this minor feature doesn't depend on the arch and it's hard to see how it could go wrong even on IA64).

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