2.4.x and SMP fails to compile (`current' undefined)

2.4.x and SMP fails to compile (`current' undefined)

[David Ford]

A person just brought up a problem in #kernelnewbies, building an SMP
kernel doesn't work very well, current is undefined.  I don't have more
time to debug it but I'll strip the config and put it up at
http://stuph.org/smp-config

-d

--
  There is a natural aristocracy among men. The grounds of this are virtue and talents. Thomas Jefferson
  The good thing about standards is that there are so many to choose from. Andrew S. Tanenbaum



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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Stephen Frost]

[-- Attachment #1: Type: text/plain, Size: 349 bytes --]

* David Ford (david@linux.com) wrote:
> A person just brought up a problem in #kernelnewbies, building an SMP
> kernel doesn't work very well, current is undefined.  I don't have more
> time to debug it but I'll strip the config and put it up at
> http://stuph.org/smp-config

	They're trying to compile SMP for Athlon/K7 (CONFIG_MK7=y).

		Stephen

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Re: 2.4.x and SMP fails to compile (`current' undefined)

[David Ford]

Mhm.  Is it worth the effort to make a dependancy on the CPU type for SMP?

</idle questions>

-d

Stephen Frost wrote:

> * David Ford (david@linux.com) wrote:
> > A person just brought up a problem in #kernelnewbies, building an SMP
> > kernel doesn't work very well, current is undefined.  I don't have more
> > time to debug it but I'll strip the config and put it up at
> > http://stuph.org/smp-config
>
>         They're trying to compile SMP for Athlon/K7 (CONFIG_MK7=y).

--
  There is a natural aristocracy among men. The grounds of this are virtue and talents. Thomas Jefferson
  The good thing about standards is that there are so many to choose from. Andrew S. Tanenbaum



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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Peter Samuelson]

[David Ford]
> Mhm.  Is it worth the effort to make a dependancy on the CPU type for
> SMP?

Yes.  'make config' should not allow unsupported configurations, at
least where convenient.

So - are any of the other chip types also incompatible with SMP support
(the Winchips, maybe)?

Peter

--- 2.4.1/arch/i386/config.in~	Tue Jan 30 14:46:04 2001
+++ 2.4.1/arch/i386/config.in	Wed Jan 31 01:08:00 2001
@@ -154,7 +154,10 @@
 
 bool 'Math emulation' CONFIG_MATH_EMULATION
 bool 'MTRR (Memory Type Range Register) support' CONFIG_MTRR
-bool 'Symmetric multi-processing support' CONFIG_SMP
+# AMD SMP - not yet
+if [ "$CONFIG_MK6" != "y" -a "$CONFIG_MK7" != "y" ]; then
+   bool 'Symmetric multi-processing support' CONFIG_SMP
+fi
 if [ "$CONFIG_SMP" != "y" ]; then
    bool 'APIC and IO-APIC support on uniprocessors' CONFIG_X86_UP_IOAPIC
    if [ "$CONFIG_X86_UP_IOAPIC" = "y" ]; then
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Tom Leete]

David Ford wrote:
> 
> Mhm.  Is it worth the effort to make a dependancy on the CPU type for SMP?
> 
> </idle questions>
> 
> -d
> 
> Stephen Frost wrote:
> 
> > * David Ford (david@linux.com) wrote:
> > > A person just brought up a problem in #kernelnewbies, building an SMP
> > > kernel doesn't work very well, current is undefined.  I don't have more
> > > time to debug it but I'll strip the config and put it up at
> > > http://stuph.org/smp-config
> >
> >         They're trying to compile SMP for Athlon/K7 (CONFIG_MK7=y).
> 

It's not an incompatibility with the k7 chip, just bad code in
include/asm-i386/string.h. in_interrupt() cannot be called from there.

I have posted a patch here many times since last May. Most recent was
Saturday.

Tom
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Peter Samuelson]

[Tom Leete]
> It's not an incompatibility with the k7 chip, just bad code in
> include/asm-i386/string.h.

So you're saying SMP *is* supported on Athlon?  Do motherboards exist?

Peter
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Tom Leete]

Peter Samuelson wrote:
> 
> [Tom Leete]
> > It's not an incompatibility with the k7 chip, just bad code in
> > include/asm-i386/string.h.
> 
> So you're saying SMP *is* supported on Athlon?  Do motherboards exist?
> 
> Peter

No, I'm saying that SMP locking etc. is compatible with Athlon. The failure
to build is not a workaround but a coding error. SMP builds for UP machines
are supposed to work.

Tom
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Peter Samuelson]

[Tom Leete]
> No, I'm saying that SMP locking etc. is compatible with Athlon.  The
> failure to build is not a workaround but a coding error.  SMP builds
> for UP machines are supposed to work.

Yes, but if SMP for Athlons is not supported, what is the point in
allowing CONFIG_SMP + CONFIG_MK7 (or CONFIG_SMP + CONFIG_MK6)?  Such a
kernel will not run on *any* SMP system, since AMD kernels do not work
on Intel.  If an AMD user really wants to carry around SMP baggage for
no reason, let him use CONFIG_M586TSC.

This is like offering MCA-bus drivers for 'make config' on SPARC.
Sure, they might compile, but nobody will have any use for them.  Thus,
we ensure that they never appear on the menus in the first place.

Peter
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Olaf Titz]

> Yes, but if SMP for Athlons is not supported, what is the point in
> allowing CONFIG_SMP + CONFIG_MK7 (or CONFIG_SMP + CONFIG_MK6)?  Such a
> kernel will not run on *any* SMP system, since AMD kernels do not work
> on Intel.  If an AMD user really wants to carry around SMP baggage for
> no reason, let him use CONFIG_M586TSC.

Authors of drivers or other kernel add-on code often have to test
their stuff on a variety of configurations. _Especially_ on an SMP
kernel even if all they have is UP.

Olaf
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[David Lang]

about the third story down is one mentioning SMP athlon boards actually
starting to show up

http://www.aceshardware.com/Spades/list_news.php?category=AMD

David Lang

On Wed, 31
Jan 2001, Tom Leete wrote:

> Date: Wed, 31 Jan 2001 05:48:31 -0500
> From: Tom Leete <tleete@mountain.net>
> To: Peter Samuelson <peter@cadcamlab.org>
> Cc: David Ford <david@linux.com>, Stephen Frost <sfrost@snowman.net>,
>      LKML <linux-kernel@vger.kernel.org>
> Subject: Re: 2.4.x and SMP fails to compile (`current' undefined)
>
> Peter Samuelson wrote:
> >
> > [Tom Leete]
> > > It's not an incompatibility with the k7 chip, just bad code in
> > > include/asm-i386/string.h.
> >
> > So you're saying SMP *is* supported on Athlon?  Do motherboards exist?
> >
> > Peter
>
> No, I'm saying that SMP locking etc. is compatible with Athlon. The failure
> to build is not a workaround but a coding error. SMP builds for UP machines
> are supposed to work.
>
> Tom
> --
> The Daemons lurk and are dumb. -- Emerson
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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>
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Peter Samuelson]

[David Lang]
> about the third story down is one mentioning SMP athlon boards
> actually starting to show up

Cool!  I want one.  So ... is there any way to know if and when Linux
kernel support will be available?  I assume AMD doesn't follow the MPS
1.x standards.

Peter
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Alan Cox]

> Cool!  I want one.  So ... is there any way to know if and when Linux
> kernel support will be available?  I assume AMD doesn't follow the MPS
> 1.x standards.

As far as I am aware they will be following the software interface. 

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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Pavel Machek]

Hi!

> > It's not an incompatibility with the k7 chip, just bad code in
> > include/asm-i386/string.h.
> 
> So you're saying SMP *is* supported on Athlon?  Do motherboards exist?

Check today's slashdot ;-).
								Pavel
-- 
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Alan Cox]

> It's not an incompatibility with the k7 chip, just bad code in
> include/asm-i386/string.h. in_interrupt() cannot be called from there.

The string.h code was fine, someone came along and put in a ridiculous loop
in the include dependancies and broke it. Nobody has had the time to untangle
it cleanly since

> I have posted a patch here many times since last May. Most recent was
> Saturday.

uninlining the code is too high a cost.
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Tom Leete]

Alan Cox wrote:
> 
> > It's not an incompatibility with the k7 chip, just bad code in
> > include/asm-i386/string.h. in_interrupt() cannot be called from there.
> 
> The string.h code was fine, someone came along and put in a ridiculous loop
> in the include dependancies and broke it. Nobody has had the time to untangle
> it cleanly since

Yes, bitrot. I don't see a rearrangement of system headers happening in 2.4.
I'm pretty sure if I committed such a patch it would have no measurable
lifetime.

> 
> > I have posted a patch here many times since last May. Most recent was
> > Saturday.
> 
> uninlining the code is too high a cost.

I question that. Athlon does branch prediction on call targets, function
calls are cheap. 3dnow saves 25%-50% of cycles on a copy. How many function
calls can be paid for with 1000 cycles or so?

My patch still inlines the standard string const_memcpy for the case of
small known length.

If I configure SMP for a UP box, performance is clearly not my first
concern. If I have a real SMP Athlon system, performance should not improve
by only using one processor.

How about we get it to build before we optimize it?

Regards,
Tom

-- 
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Andre Hedrick]

Make it and I will care and post it on kernel.org for you.
I need that patch soon.

On Thu, 1 Feb 2001, Tom Leete wrote:

> Alan Cox wrote:
> > 
> > > It's not an incompatibility with the k7 chip, just bad code in
> > > include/asm-i386/string.h. in_interrupt() cannot be called from there.
> > 
> > The string.h code was fine, someone came along and put in a ridiculous loop
> > in the include dependancies and broke it. Nobody has had the time to untangle
> > it cleanly since
> 
> Yes, bitrot. I don't see a rearrangement of system headers happening in 2.4.
> I'm pretty sure if I committed such a patch it would have no measurable
> lifetime.
> 
> > 
> > > I have posted a patch here many times since last May. Most recent was
> > > Saturday.
> > 
> > uninlining the code is too high a cost.
> 
> I question that. Athlon does branch prediction on call targets, function
> calls are cheap. 3dnow saves 25%-50% of cycles on a copy. How many function
> calls can be paid for with 1000 cycles or so?
> 
> My patch still inlines the standard string const_memcpy for the case of
> small known length.
> 
> If I configure SMP for a UP box, performance is clearly not my first
> concern. If I have a real SMP Athlon system, performance should not improve
> by only using one processor.
> 
> How about we get it to build before we optimize it?
> 
> Regards,
> Tom
> 
> -- 
> The Daemons lurk and are dumb. -- Emerson
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> 

Andre Hedrick
Linux ATA Development

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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Tom Leete]

Andre Hedrick wrote:
> 
> Make it and I will care and post it on kernel.org for you.
> I need that patch soon.
> 
> On Thu, 1 Feb 2001, Tom Leete wrote:
> 
> > Alan Cox wrote:
> > > The string.h code was fine, someone came along and put in a ridiculous loop
> > > in the include dependancies and broke it. Nobody has had the time to untangle
> > > it cleanly since
> >
> > Yes, bitrot. I don't see a rearrangement of system headers happening in 2.4.
> > I'm pretty sure if I committed such a patch it would have no measurable
> > lifetime.

Hi Andre,

I meant that nobody should be reshuffling 2.4 headers now, didn't intend to
sound like I take that personally.

I'll take a look. I may be able to do something with include guards or other
#defines + multiple passes. We already have the multiple passes.

I think my arguments for the present patch are good. I'm making a mod of
Arjan's athlon.c to see if I'm right. If you have a suggestion for another
benchmark, I'd like to hear about it. Whatever the results, I'll post them
here.

Glad if whatever comes out is useful to you.

Cheers,
Tom

-- 
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Alan Cox]

> > uninlining the code is too high a cost.
> 
> I question that. Athlon does branch prediction on call targets, function
> calls are cheap. 3dnow saves 25%-50% of cycles on a copy. How many function
> calls can be paid for with 1000 cycles or so?
> 
> My patch still inlines the standard string const_memcpy for the case of
> small known length.

We have a very large number of memcpy's of unknown short length (often in
interrupts) that are close to branches. A lot of

	if(foo==NULL)
		return
	memcpy(..

stuff for example.

Im more than happy for someone to do the benches and prove me wrong

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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Tom Leete]

Alan Cox wrote:
> 
> We have a very large number of memcpy's of unknown short length (often in
> interrupts) that are close to branches. A lot of
> 
>         if(foo==NULL)
>                 return
>         memcpy(..
> 
> stuff for example.
> 
> Im more than happy for someone to do the benches and prove me wrong

Agreed, that is a bad case, and there is overhead for it in my patch. I'm
putting together some metrics, will post results here.

Regards,
Tom

-- 
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[David Lang]

probably not now that SMP athlon boards are supposed to be starting to be
available.

David Lang

On Tue, 30 Jan 2001, David Ford wrote:

> Date: Tue, 30 Jan 2001 20:37:02 -0800
> From: David Ford <david@linux.com>
> To: Stephen Frost <sfrost@snowman.net>
> Cc: LKML <linux-kernel@vger.kernel.org>
> Subject: Re: 2.4.x and SMP fails to compile (`current' undefined)
>
> Mhm.  Is it worth the effort to make a dependancy on the CPU type for SMP?
>
> </idle questions>
>
> -d
>
> Stephen Frost wrote:
>
> > * David Ford (david@linux.com) wrote:
> > > A person just brought up a problem in #kernelnewbies, building an SMP
> > > kernel doesn't work very well, current is undefined.  I don't have more
> > > time to debug it but I'll strip the config and put it up at
> > > http://stuph.org/smp-config
> >
> >         They're trying to compile SMP for Athlon/K7 (CONFIG_MK7=y).
>
> --
>   There is a natural aristocracy among men. The grounds of this are virtue and talents. Thomas Jefferson
>   The good thing about standards is that there are so many to choose from. Andrew S. Tanenbaum
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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Re: 2.4.x and SMP fails to compile (`current' undefined)

[Jeff Garzik]

On Wed, 31 Jan 2001, David Lang wrote:
> probably not now that SMP athlon boards are supposed to be starting to be
> available.

They already are...  there is a dual Athlon box at the MDK booth here at
LinuxWorld.

	Jeff




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