Debian drops support for sparc

Debian drops support for sparc

[Sam Ravnborg]

Hi all.

Debian have decided to drop support for sparc.
See additional details  here: https://lists.debian.org/debian-sparc/2015/07/msg00023.html

To the best of my understanding this is 32 bit userland
on top of sparc64 kernel that is dropped.

In Debian ports there is a sparc64 port which is 64-bit
userland on top of sparc64 kernel.
There are talks about improving support for the sparc64
ports but I have not read anything conclusive.

Additional details can be found the following bug report:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bugt5938

A major issue is that gcc-4.9 cannot be built for sparc
for reasons that I failed to follow.

When I read: https://bugs.debian.org/cgi-bin/bugreport.cgi?bugt5938#48
I get the impression that this is for the most part
bugs that may have been fixed recently.
The regression testing doen by Meelis Roos has shown
that things has improved a lot the last couple of months
if I recall correct. So sad that Debian drops sparc support now
when these fixes may not have propagated.

In a G+ post I also referred to the memcpy / FPU register
corruption bug that David only recently were able to reproduce.
I am not sure how much this bug influence the lack of stability
that people see when using sparc64 kernels.
See details here: http://marc.info/?t\x143382318800002&r=1&w=2

	Sam

Re: Debian drops support for sparc

[Josip Rodin]

On Thu, Jul 30, 2015 at 04:04:54PM +0200, Sam Ravnborg wrote:
> Hi all.
> 
> Debian have decided to drop support for sparc.
> See additional details  here: https://lists.debian.org/debian-sparc/2015/07/msg00023.html
> 
> To the best of my understanding this is 32 bit userland
> on top of sparc64 kernel that is dropped.
> 
> In Debian ports there is a sparc64 port which is 64-bit
> userland on top of sparc64 kernel.
> There are talks about improving support for the sparc64
> ports but I have not read anything conclusive.
> 
> Additional details can be found the following bug report:
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bugt5938
> 
> A major issue is that gcc-4.9 cannot be built for sparc
> for reasons that I failed to follow.

That was a problem for about five months last year, afterwards it was
resolved, though some issues happened later as well:
https://buildd.debian.org/status/logs.php?pkg=gcc-4.9&arch=sparc

The next version also had a spotty coverage:
https://buildd.debian.org/status/logs.php?pkg=gcc-5&arch=sparc

But I think the focus should probably be on the sheer redness of the sparc
columns at:
https://release.debian.org/stretch/arch_qualify.html (prospective release)
https://release.debian.org/jessie/arch_qualify.html (current release)

So, the recurring issues of the number of porters, default compiler,
and buildd kernel stability are critical.

And probably the fact that nobody even responded to
https://lists.debian.org/debian-sparc/2015/07/msg00012.html did not help.
On that note, let's Cc: that list :)

-- 
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Re: Debian drops support for sparc

[Sam Ravnborg]

> But I think the focus should probably be on the sheer redness of the sparc
> columns at:
> https://release.debian.org/jessie/arch_qualify.html (current release)

From the link above:
"
sparc

Upstream Support

According to the gcc maintainer 32bit code generation as we use it is no longer supported upstream and we should aim for a switch to 64bit userland anytime soon.
"

Is it correct that 32bit gcc is no longer maintained?
I have seen nothing on gcc mailaing list about this.

	Sam

Re: Debian drops support for sparc

[Patrick Baggett]

On Thu, Jul 30, 2015 at 11:48 AM, Sam Ravnborg <sam@ravnborg.org> wrote:
>> But I think the focus should probably be on the sheer redness of the sparc
>> columns at:
>> https://release.debian.org/jessie/arch_qualify.html (current release)
>
> >From the link above:
> "
> sparc
>
> Upstream Support
>
> According to the gcc maintainer 32bit code generation as we use it is no longer supported upstream and we should aim for a switch to 64bit userland anytime soon.
> "
>
> Is it correct that 32bit gcc is no longer maintained?
> I have seen nothing on gcc mailaing list about this.
>

I've challenged this assertion, too. I don't see any evidence of it
being true. 32-bit userland makes sense for most RISC architectures
because the increased code/memory size for switching to 64-bit apps is
not justified in most cases. x86 is the weird case that 64-bit code
can run faster due to more registers, an efficient calling convention,
and %rip relative addressing. Even Solaris 10+ (which only supports
64-bit sparc kernels) has a 32-bit userland for this reason. I think
that, of all people, the gcc sparc maintainers, understand this.

I can only guess what "32bit code generation as we use it" means, but
I doubt that it means "32-bit code targeting sparcv9 ISA".

Re: Debian drops support for sparc

[David Miller]

From: Sam Ravnborg <sam@ravnborg.org>
Date: Thu, 30 Jul 2015 18:48:24 +0200

> From the link above:
> "
> sparc
> 
> Upstream Support
> 
> According to the gcc maintainer 32bit code generation as we use it is no longer supported upstream and we should aim for a switch to 64bit userland anytime soon.
> "
> 
> Is it correct that 32bit gcc is no longer maintained?
> I have seen nothing on gcc mailaing list about this.

That really can't be true.

Re: Debian drops support for sparc

[Josip Rodin]

On Thu, Jul 30, 2015 at 06:48:24PM +0200, Sam Ravnborg wrote:
> > But I think the focus should probably be on the sheer redness of the sparc
> > columns at:
> > https://release.debian.org/jessie/arch_qualify.html (current release)
> 
> >From the link above:
> "
> sparc
> 
> Upstream Support
> 
> According to the gcc maintainer 32bit code generation as we use it is no longer supported upstream and we should aim for a switch to 64bit userland anytime soon.
> "
> 
> Is it correct that 32bit gcc is no longer maintained?
> I have seen nothing on gcc mailaing list about this.

That's from jessie, which was already released. The said note has been
removed from the list for stretch.

The problem is that numerous other issues - haven't.

-- 
     2. That which causes joy or happiness.

Re: Debian drops support for sparc

[David Miller]

From: Josip Rodin <joy@entuzijast.net>
Date: Thu, 30 Jul 2015 21:22:30 +0200

> On Thu, Jul 30, 2015 at 06:48:24PM +0200, Sam Ravnborg wrote:
>> > But I think the focus should probably be on the sheer redness of the sparc
>> > columns at:
>> > https://release.debian.org/jessie/arch_qualify.html (current release)
>> 
>> >From the link above:
>> "
>> sparc
>> 
>> Upstream Support
>> 
>> According to the gcc maintainer 32bit code generation as we use it is no longer supported upstream and we should aim for a switch to 64bit userland anytime soon.
>> "
>> 
>> Is it correct that 32bit gcc is no longer maintained?
>> I have seen nothing on gcc mailaing list about this.
> 
> That's from jessie, which was already released. The said note has been
> removed from the list for stretch.

The thing is, it makes no sense to go to a 64-bit only userland
distribition.

What does make sense is maybe only supporting sparc64 kernels,
but with a userland that is built 32-bit targetting v8plus.

> The problem is that numerous other issues - haven't.

It would be nice to narrow things down to the real issues.

The only major blocker I know of is the kernel FPU issue, which is
what I'm spending all of my sparc cycles on.

Re: Debian drops support for sparc

[Kjetil Oftedal]

On 30/07/2015, David Miller <davem@davemloft.net> wrote:
> From: Josip Rodin <joy@entuzijast.net>
> Date: Thu, 30 Jul 2015 21:22:30 +0200
>
>> On Thu, Jul 30, 2015 at 06:48:24PM +0200, Sam Ravnborg wrote:
>>> > But I think the focus should probably be on the sheer redness of the
>>> > sparc
>>> > columns at:
>>> > https://release.debian.org/jessie/arch_qualify.html (current release)
>>>
>>> >From the link above:
>>> "
>>> sparc
>>>
>>> Upstream Support
>>>
>>> According to the gcc maintainer 32bit code generation as we use it is no
>>> longer supported upstream and we should aim for a switch to 64bit
>>> userland anytime soon.
>>> "
>>>
>>> Is it correct that 32bit gcc is no longer maintained?
>>> I have seen nothing on gcc mailaing list about this.
>>
>> That's from jessie, which was already released. The said note has been
>> removed from the list for stretch.
>
> The thing is, it makes no sense to go to a 64-bit only userland
> distribition.
>
> What does make sense is maybe only supporting sparc64 kernels,
> but with a userland that is built 32-bit targetting v8plus.
>
>> The problem is that numerous other issues - haven't.
>
> It would be nice to narrow things down to the real issues.
>
> The only major blocker I know of is the kernel FPU issue, which is
> what I'm spending all of my sparc cycles on.
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>

Hi,

As far as I remember Debian dropped Sparc32 support quite a few years ago.
So I guess what is being dropped this time around is the official support for
64-bit kernel + 32-bit/v8plus userland.

Then only the unofficial port of 64-bit kernel + 64-bit userland remains.

Regards,
Kjetil Oftedal

Re: Debian drops support for sparc

[Josip Rodin]

On Thu, Jul 30, 2015 at 02:53:33PM -0700, David Miller wrote:
> > The problem is that numerous other issues - haven't.
> 
> It would be nice to narrow things down to the real issues.

Well, let me try to clarify what I've already said:

* More people have to become what is known as sparc porters in Debian. That
  means being involved in making sure sparc package build failures in Debian
  are attended to - as opposed to currently listed 1 single person.

* The default compiler is apparently stuck on an old version, or was at some
  point? I can't verify that at https://packages.debian.org/gcc Someone
  should investigate what went wrong there - judging by the previous
  difference in opinions regarding whether 32-bit userland is viable,
  it would probably be necessary to take that to the debian-gcc list

* The buildd kernels haven't been stable enough. Someone should talk to
  the buildd maintainers at sparc@buildd.debian.org to see what the status
  is.

Perhaps this all seems like not 'real' issues to kernel people, but there's
nothing more real for Debian sparc users and buildd maintainers than the
issue of nobody being around in the standard Debian communication channels
to hear them scream :)

-- 
     2. That which causes joy or happiness.

Re: Debian drops support for sparc

[Josip Rodin]

On Fri, Jul 31, 2015 at 08:20:41AM +0200, Kjetil Oftedal wrote:
> So I guess what is being dropped this time around is the official support for
> 64-bit kernel + 32-bit/v8plus userland.
> 
> Then only the unofficial port of 64-bit kernel + 64-bit userland remains.

That seems a bit misleading, because I don't see what would be preventing
sparc from ultimately reappearing together with sparc64 on debian-ports.org.

Given that it already has a bunch of buildds and still has a better archive
coverage (the percentage of total packages build on sparc compared to
total), that's a fairly solid foundation.

-- 
     2. That which causes joy or happiness.