[parisc-linux] Re: Support for 2.4.x kernels on hppa

[parisc-linux] Re: Support for 2.4.x kernels on hppa

[Ulrich Teichert]

Hi,

>I'd like to take an informal "survey" of what kernel versions people are
>using....

Mostly, 2.4.17, the debian default kernel or 2.4.25/6-pa*.

>For the last year or two, most of the kernel developers have been
>focusing on the 2.5/2.6 kernels; as a result many bugs that were
>presented in both 2.4 and 2.6 kernels have been only fixed in 2.6. This
>is understandable given that there are only a few active parisc-linux
>kernel developers.... moving foward it is becoming more difficult to
>support the 2.4.x kernels, and we are finding that we need to put in
>some not-so-nice workarounds in some userspace tools to cope with bugs
>in the 2.4 kernel.

I understand the pain to maintain 2 trees. I once had to maintain 4
separate trees (in SCCS - ouch), which at least doubled the pain, but
I think it grows exponential.

>So, the question is, how many of you run parisc-linux on 2.4
>"production" systems and "cannot" switch to 2.6? At last count there are
>about 1200 registered parisc-linux users on the p-l website, and i know
>at least some folks run parisc-linux on decent-sized clusters... so we 
>definitely don't want to break things if people are using 2.4 actively 
>on these systems and have legitimate reasons not to move to 2.6....

Right now, I use debian woody on all my boxes and upgrading to testing
is a PITA for me, as I only have an ISDN line (*one* line - 64k). I usually
install from CD-ROM.

>If you are one of those people who really care about 2.4 support, please
>speak up now! 

Actually, I only have two HPPA production systems, my firewall (a 712/80)
and a 240, everything else is for fooling around - but both are on debian
woody and more or less tied to 2.4. Or are there offical woody backports of
the toolchain needed for 2.6 (preferred under 1G...)?

CU,
Uli
-- 
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[William Waites]

On Mon, May 24, 2004 at 11:32:27AM -0700, Randolph Chung wrote:
> Hi all,
> 
> I'd like to take an informal "survey" of what kernel versions people are
> using....

2.4.25-pa1 on a C3000

> If you are one of those people who really care about 2.4 support, please
> speak up now! 

At the time, I was working on some things that required
SysV streams, and LiS won't run on 2.6. Now I don't need
LiS anymore. That said, the box is quite stable, so I
don't plan to touch the kernel unless a compelling reason
presents itself, in which case a change to 2.6 won't cause
any additional pain.

/w
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Grant Grundler]

On Mon, May 24, 2004 at 03:32:05PM -0400, William Waites wrote:
...
> That said, the box is quite stable, so I
> don't plan to touch the kernel unless a compelling reason
> presents itself, in which case a change to 2.6 won't cause
> any additional pain.

Disk devices are enumerated differently on 2.6.
ie some minor pain to find the root disk again
if one isn't lucky.

grant
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Grant Grundler]

On Tue, May 25, 2004 at 01:36:10PM -0400, William Waites wrote:
...
> At this moment I am unsure of the state of palo in
> debian/testing...

AFAICT, palo 1.5 is has not been accepted into "testing" yet.

But I strongly reccomend installing 1.5 since it clearly fixes
the only currently known bug in 1.4 and adds some nice features
like "ls" command (kudos to james again).

grant
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[John David Anglin]

> If you are one of those people who really care about 2.4 support, please
> speak up now! 

Here is a little background on this issue.  Randolph has done a
considerable amount of work to port libffi to the PA, and then add
unwind and other support support to libjava.  This gives us a
working Java implementation.  Thanks, Randolph!

This work is currently being integrated into GCC 3.5.  This is working
well with 2.6, but we have problems with unwinding through signal
frames on 2.4.  64-bit support is completely broken.  On at least
some 32-bit kernels, we end up with hung processes that can bring
the system to its knees.

We are having a little debate as to whether we need to support 2.4,
given that GCC 3.5 probably won't be out for a year or so.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Randolph Chung]

> Here is a little background on this issue.  Randolph has done a
> considerable amount of work to port libffi to the PA, and then add
> unwind and other support support to libjava.  This gives us a
> working Java implementation.  Thanks, Randolph!

you are welcome.

it's not just gcc though; gdb has almost the same bits of signal
unwinding code so it has the same issues. there are also other instances
where things are working in 2.6 but not in 2.4 (especially with all the
compat work for 32-bit userspace/64-bit kernel that has gone into 2.6).

randolph
-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/


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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Ulrich Teichert]

Hi,

[del]
>Here is a little background on this issue.  Randolph has done a
>considerable amount of work to port libffi to the PA, and then add
>unwind and other support support to libjava.  This gives us a
>working Java implementation.  Thanks, Randolph!

Yupp, that's a step forward.

>This work is currently being integrated into GCC 3.5.  This is working
>well with 2.6, but we have problems with unwinding through signal
>frames on 2.4.  64-bit support is completely broken.  On at least
>some 32-bit kernels, we end up with hung processes that can bring
>the system to its knees.

Well, I could only speak for myself and my little boxes, and I would
say only do the absolute minimum required (like security fixes). Getting
new gcc 3.5 (or gdb) code to work, I would not count as necessary.

>We are having a little debate as to whether we need to support 2.4,
>given that GCC 3.5 probably won't be out for a year or so.

Just make it clear in the release notes and let the compile fail on
2.4 with an #error, IMHO. Does that sound too lazy ?-)

HTH,
Uli
-- 
Dipl. Inf. Ulrich Teichert|e-mail: Ulrich.Teichert@gmx.de
Stormweg 24               |listening to: Noticable One (Rotten Apples)
24539 Neumuenster, Germany|Obstacle 1 (Interpol) Paranoia (N.Y. Rel-X)
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Thibaut VARENE]

On Mon, 24 May 2004 11:32:27 -0700
"Randolph Chung" <tausq@debian.org> wrote:

> Hi all,
> 
> I'd like to take an informal "survey" of what kernel versions people
> are using....
[snip]
> If you are one of those people who really care about 2.4 support,
> please speak up now! 

We're mostly using 2.4 on our production and devel machines, as the
following page shows:

http://www.pateam.org/realisations.html

Some of them could be switched to 2.6, but not the SMP ones, which are
64bit btw, until SMP is proven efficient on 2.6.

HTH,


Thibaut VARENE
The PA/Linux ESIEE Team
http://www.pateam.org/
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[parisc-linux] Re: Support for 2.4.x kernels on hppa

[Steve Bromwich]

On Mon, 24 May 2004, Randolph Chung wrote:

> So, the question is, how many of you run parisc-linux on 2.4
> "production" systems and "cannot" switch to 2.6?

I'm running a 715/100XC and 2.4.25-pa1, which has been running rock solid
now for 56 days. It's my own personal SMTP/POP/IMAP server, file server,
print server, name server, webmail... basically all sorts of little
oddball services that make my life at home a little easier. I also have a
few friends using it, which is the only reason I'd call it anything near
production (but I figured you'd be interested in comments from home users
too). I haven't upgraded to 2.6 because (a) I have very little time at
home to twiddle with things like this these days, and (b) I'm taking the
view of "it's running happily so there's no need for me to change". I
think I'll probably upgrade the box around Christmas or so. Alternatively
I may be able to lay my hands on a D370 (as mentioned in passing) which
I'll probably use to clone my 715 onto and upgrade that to 2.6.

I've also got a J200 I keep meaning to upgrade. So many toys, so little
time... :-/ That machine also generates enough heat that I usually only
run that in the winter, as the heat output from my little server room goes
into the heat exchanger - 45 minutes of that and the disk array running
and the furnace switches off!

Cheers, Steve
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Guy Martin]

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On Mon, 24 May 2004 11:32:27 -0700
Randolph Chung <tausq@debian.org> wrote:

> I'd like to take an informal "survey" of what kernel versions people
> are using....

I use a 2.6 on a A440 and B180l and a C3600.
I remember having trouble with a J5000 but it was some time ago and I
guess my problem was the SMP enabled.

I'd like to use it on my D270 and on a K360 but there are scsi problems
atm. They both suffer of the same problem described by Joel Soete.

Also, a gentoo user wasn't able to boot a 2.6 on a 735/120. Palo (1.5)
display "If it's the last message ..." and nothing more while it works
well with a 2.4. I'll try myself later on my 735/99 which is down atm.


I'd like to add that despite the scsi problem, I can't still produce
livecd (the gentoo installation cd) using 2.6 because of the numerous
default config. If I remember correctly, if I enable some HIL stuff,
the kernel loops or crash at boot on my b180l.

> If you are one of those people who really care about 2.4 support,
> please speak up now! 

Personaly, I don't care about 2.4 even if 2.6 doesn't have SMP. With a
2.4, my D270 compiles things slower with SMP than without. I also have
other problems with SMP like packet loss to localhost, making portmap
and other socket daeùon unusable.


hth

-- 
Guy Martin
Gentoo Linux - HPPA port Lead / IPv6 team
Lug Charleroi (Belgium)

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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Michael S. Zick]

On Tue May 25 2004 05:21, Guy Martin wrote:
> On Mon, 24 May 2004 11:32:27 -0700
> > please speak up now!
>
> Personaly, I don't care about 2.4 even if 2.6 doesn't have SMP. With a
> 2.4, my D270 compiles things slower with SMP than without.=20

Hmm... Probably related to the slow fork/exec on hppa and the effect
of SMP load balancing in kernel scheduler -
There has been continuous work to improve fork/exec - I don't know if
the changes have been applied to 2.4.x systems - others on this list
will know.

> I also have=20
> other problems with SMP like packet loss to localhost, making portmap
> and other socket dae=F9on unusable.
2.4?? or 2.6??  (2.6.x has i/o scheduling)

Mike
>
>
> hth
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Guy Martin]

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On Tue, 25 May 2004 12:12:03 -0500
"Michael S. Zick" <mszick@goquest.com> wrote:

> On Tue May 25 2004 05:21, Guy Martin wrote:
> > On Mon, 24 May 2004 11:32:27 -0700
> > > please speak up now!
> >
> > Personaly, I don't care about 2.4 even if 2.6 doesn't have SMP. With
> > a 2.4, my D270 compiles things slower with SMP than without. 
> 
> Hmm... Probably related to the slow fork/exec on hppa and the effect
> of SMP load balancing in kernel scheduler -
> There has been continuous work to improve fork/exec - I don't know if
> the changes have been applied to 2.4.x systems - others on this list
> will know.

Afaik, it was applied to kernel post 2.6.3.

> > I also have 
> > other problems with SMP like packet loss to localhost, making
> > portmap and other socket daeùon unusable.
> 2.4?? or 2.6??  (2.6.x has i/o scheduling)

This is with a 2.4 SMP kernel on my D270/2. The problem disapear when I
use a non-SMP kernel.

-- 
Guy Martin
Gentoo Linux - HPPA port Lead / IPv6 team
Lug Charleroi (Belgium)

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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[John David Anglin]

> Just make it clear in the release notes and let the compile fail on
> 2.4 with an #error, IMHO. Does that sound too lazy ?-)

Yes.  It's a runtime issue and nobody seems to read the release notes.

Dave
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Grant Grundler]

On Mon, May 24, 2004 at 05:47:31PM -0400, John David Anglin wrote:
> > Just make it clear in the release notes and let the compile fail on
> > 2.4 with an #error, IMHO. Does that sound too lazy ?-)
> 
> Yes.  It's a runtime issue and nobody seems to read the release notes.

In other words, the next Debian release based on gcc 3.5 or later
will require a 2.6 parisc kernel?

If that's the case, we are looking several years out and I personally
don't see a problem with it. Folks can continue to run "sarge"
for a long time after that if they are happy with it.

Gentoo folks will have to "pin" the compiler rev if they want
to use 2.4 kernels.

I trust we don't have to worry about HPUX, HP-RT, or MPE and
issues with gcc/java? :^)

thanks,
grant
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Randolph Chung]

> In other words, the next Debian release based on gcc 3.5 or later
> will require a 2.6 parisc kernel?

Not require, but some features will only work properly with a 2.6.x
kernel. Some features may cause unexpected behaviors with 2.4 kernels.

Let me explain this in a bit more detail.

As Dave mentioned, there is a case in gcc which is currently broken when
running 2.4 kernels, because sigcontext handling was broken in 2.4
kernels for 64-bit kernels. Carlos fixed this in 2.6.x (thanks Carlos).

The signal trampoline layout also changed in 2.6.x kernels, breaking 
backward compatibility for userspace applications that need to process 
the signal context structure. This has come up not only for gcc but for
some other applications (this topic comes up from time to time on 
debian-hppa).

Currently there is code in gcc to handle 32-bit 2.4 kernels, 32-bit 2.6
kernels and 64-bit 2.6 kernels. However, it appears that with 2.4
kernels there are still some bugs related to either mmap, signal
handling or unaligned trap handling that causes the gcc testsuite to
hang the machine from time to time. If you run a 64-bit 2.4 kernel than
some of the gcc unwinding stuff will not work at all.

It is certainly possible to fix this, if someone is so inclined.... but
there are many bugs to fix in 2.6, and i still have 70+ gdb bugs to fix
:) so it'll have to be someone else....

In a grand scheme of things, there is just a small portion of userspace
that will not work properly with a 2.4 kernel. Probably 95+% of users
will not notice... but it is still broken, and we need to make sure this
is clear and people understand that if something doesn't work, the only
"solution" may be to upgrade to 2.6.x kernels (unless someone steps up
to say they will maintain the 2.4.x kernel series for hppa). gcc is just
one example of where this will come up, there are probably some other
cases where things will be fixed with 2.6 kernels and won't work with
2.4. I don't think anyone will break anything intentionally for 2.4, but
most of the active developers are probably doing most of their work on
2.6, so 2.4 is not nearly as well tested.

I should also point out that, really, this is nothing new, we've
probably been operating in this mode for the last year; it's just
never been made explicit.. :)

thanks,
randolph
-- 
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Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[John David Anglin]

> I trust we don't have to worry about HPUX, HP-RT, or MPE and
> issues with gcc/java? :^)

Well, it shouldn't be too much additional work to support gcc/java
under HPUX.  There have been some experiments with unwinding signal
frames for Ada.

Dave
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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[James Bottomley]

On Tue, 2004-05-25 at 00:42, Randolph Chung wrote:
> I should also point out that, really, this is nothing new, we've
> probably been operating in this mode for the last year; it's just
> never been made explicit.. :)

Well, I think it's basically the democracy of open source.  I did quite
a few (although by no means all) of the kernel fixes to get the
gcc/glibc tests to pass on 2.6, I have no interest in fixing it on 2.4,
but if someone else cares enough, they will...

James


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Re: [parisc-linux] Support for 2.4.x kernels on hppa

[Carlos O'Donell]

> As Dave mentioned, there is a case in gcc which is currently broken when
> running 2.4 kernels, because sigcontext handling was broken in 2.4
> kernels for 64-bit kernels. Carlos fixed this in 2.6.x (thanks Carlos).
> 
> The signal trampoline layout also changed in 2.6.x kernels, breaking 
> backward compatibility for userspace applications that need to process 
> the signal context structure. This has come up not only for gcc but for
> some other applications (this topic comes up from time to time on 
> debian-hppa).
> 
> Currently there is code in gcc to handle 32-bit 2.4 kernels, 32-bit 2.6
> kernels and 64-bit 2.6 kernels. However, it appears that with 2.4
> kernels there are still some bugs related to either mmap, signal
> handling or unaligned trap handling that causes the gcc testsuite to
> hang the machine from time to time. If you run a 64-bit 2.4 kernel than
> some of the gcc unwinding stuff will not work at all.

Thanks for all the help! Yeah, the sigcontext fixes wouldn't have been
possible without James Bottomley's cleanups. A backport of all that code
is a lengthy project, with a lot of reboot cycles.

Since sigcontext is an opaque structures, and we don't have
set/get/make/swap context calls we only broke those programs that parsed
sigcontext by themselves. I apologize for that, but it was the only way
to implement restartable system calls without a race condition (or
rather 2 race conditions, we still have a race I think).

c.

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