[parisc-linux] A warning about NPTL pthreaddefs.h

[parisc-linux] A warning about NPTL pthreaddefs.h

[Carlos O'Donell]

Randolph,

A warning that the pthreaddefs.h might be horribly wrong. I remember a
long while ago adding padding the structures so they matched the size
of the linuxthread types (atleast the lock position).

This padding is not correct, we would need to pull into our tree the
static mutex initializers so they are correctly sized aswell.

If you look at the build logs there are warnings about this.

I'm trying a build with the lock padding removed, but it still fails
all over the place, but atleast this time there are no apparent
deadlocks!!! Yay!

Cheers,
Carlos.
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[parisc-linux] Re: A warning about NPTL pthreaddefs.h

[Randolph Chung]

> A warning that the pthreaddefs.h might be horribly wrong. I remember a
> long while ago adding padding the structures so they matched the size
> of the linuxthread types (atleast the lock position).
> 
> This padding is not correct, we would need to pull into our tree the
> static mutex initializers so they are correctly sized aswell.

fwiw,i don't think we need to worry about making the structs the same as 
linuxthreads (if that is even possible...), after all you cannot run a 
linuxthreads binary against nptl libs or vice versa...

randolph
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[parisc-linux] Re: A warning about NPTL pthreaddefs.h

[Carlos O'Donell]

On 7/17/06, Randolph Chung <randolph@tausq.org> wrote:
> > A warning that the pthreaddefs.h might be horribly wrong. I remember a
> > long while ago adding padding the structures so they matched the size
> > of the linuxthread types (atleast the lock position).
> >
> > This padding is not correct, we would need to pull into our tree the
> > static mutex initializers so they are correctly sized aswell.
>
> fwiw,i don't think we need to worry about making the structs the same as
> linuxthreads (if that is even possible...), after all you cannot run a
> linuxthreads binary against nptl libs or vice versa...

Yes, yes you are. Ulrich's first post of NPTL 1.0 says:
---
The thread library is designed to be binary compatible with the old
LinuxThreads implementation.  This compatibility obviously has some
limitations.  In places where the LinuxThreads implementation diverged
from the POSIX standard incompatibilities exist.  Users of the old
library have been warned from day one that this day will come and code
which added work-arounds for the POSIX non-compliance better be
prepared to remove that code.  The visible changes of the library
include:
---

And he goes on to list things which are not compatible.

Wether or not PARISC can do this is another question. It might not be
possible due to our lock[4] and LDCW linuxthreads implementation.

c.
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[parisc-linux] Re: A warning about NPTL pthreaddefs.h

[Carlos O'Donell]

On 7/17/06, Randolph Chung <randolph@tausq.org> wrote:
> > A warning that the pthreaddefs.h might be horribly wrong. I remember a
> > long while ago adding padding the structures so they matched the size
> > of the linuxthread types (atleast the lock position).
> >
> > This padding is not correct, we would need to pull into our tree the
> > static mutex initializers so they are correctly sized aswell.
>
> fwiw,i don't think we need to worry about making the structs the same as
> linuxthreads (if that is even possible...), after all you cannot run a
> linuxthreads binary against nptl libs or vice versa...

Regardless we still bomb out on a lot of the tests :)

c.
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Re: [parisc-linux] Re: A warning about NPTL pthreaddefs.h

[Jeff Bailey]

On Tue, Jul 18, 2006 at 08:19:12AM +0800, Randolph Chung wrote:
> >A warning that the pthreaddefs.h might be horribly wrong. I remember a
> >long while ago adding padding the structures so they matched the size
> >of the linuxthread types (atleast the lock position).
> >
> >This padding is not correct, we would need to pull into our tree the
> >static mutex initializers so they are correctly sized aswell.
> 
> fwiw,i don't think we need to worry about making the structs the same as 
> linuxthreads (if that is even possible...), after all you cannot run a 
> linuxthreads binary against nptl libs or vice versa...

On other platforms, LT binaries generally run on the NPTL libs.  If we
break this, then there'll be an interesting upgrade problem for the
distros tosolve that they haven't needed to do on other archs.

Tks,
Jeff Bailey

-- 
I do not agree with a word you say, but I will defend to the death your
right to say it. 
 - Voltaire
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Re: [parisc-linux] Re: A warning about NPTL pthreaddefs.h

[Carlos O'Donell]

On 7/18/06, Jeff Bailey <jbailey@raspberryginger.com> wrote:
> On other platforms, LT binaries generally run on the NPTL libs.  If we
> break this, then there'll be an interesting upgrade problem for the
> distros tosolve that they haven't needed to do on other archs.

It's technically possible... maybe...

1. Use 1 for locked, and 0 for unlocked in our integer sized locks (to match LT)
2. Add padding in the form of a union, aligned to 16.
3. Select the aligned lock word, but use CAS instead of LDCW.

This would give the same semantics as LT, and probably preserve binary
compatiblity. The only performance loss is calculated the aligned
word.

c.
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