Re: [hpoj-devel] kernel drivers broken with SMP

[Burkhard K. <bu...@bu...>]

From: Burkhard Kohl <bu...@bu...>
Message-Id: <200...@bu...>
Subject: Re: [hpoj-devel] kernel drivers broken with SMP
In-Reply-To: <200009180732.AAA13385@axel.local> from David Paschal at "Sep 18,
	2000 00:32:56 am"
To: hpo...@li... 
Date: Tue, 19 Sep 2000 20:39:54 +0200 (CEST)
X-Mailer: ELM [version 2.4ME+ PL60 (25)]

David Paschal
> Hi, Gerhard and Burkhard.  Thanks for providing the information regarding
> the SMP and 2.4-kernel problems, which seem to be interrelated.  You seem
> to have a much better understanding of kernel issues than I do.  If either
> or both of you would be willing to work towards a solution to these problems,
> that would be greatly appreciated, and would leave me more time to develop
> scanning support for the scrollfed MFPs, which I started working on last week.
> :-)
> 
I started to work on the SMP/2.4 issues - might take some time, since
I can do this only in my spare time. But I have to point out that I 
have no SMP system to test on and that I am less than familiar with 
the locking necessities of socket related issues. And I am not what 
would be called a *real* kernel hacker.

> ger...@mc... said:
> > 1. A driver, that has been compiled for an UP kernel cannot be used
> > with
> >    an SMP kernel (and vice versa).
> >    An SMP module must be compiled using kernel header files
> >    which are configured for SMP (-> CONFIG_SMP) and with the
> >    compiler flag -D__SMP__
> 
> >    Is the current Makefile prepared to compile either SMP or UP
> > modules? 
> Good point.  Currently, ieee12844/Makefile.in starts with the following lines:
> 	SMP=
> 	# SMP=-D__SMP__
> 
> 	CFLAGS = -O @INCLUDE_CMDLINE@ -Wall -Wstrict-prototypes -D__KERNEL__ \
> 		 -DMODULE -DEXPORT_SYMTAB $(SMP)
> As it stands now, the __SMP__ symbol is not passed to kernel includes.
> So, Alexander, one thing you could try is uncommenting out the second line.
> If you modify Makefile, then you can recompile right away but the change
> will be lost the next time you run the ./configure script.  If you modify
> Makefile.in, then you will need to re-run ./configure before you try
> recompiling.  Since this problem appears in all versions, you might as well
> use the latest (0.6).
This could be cured by looking at CONFIG_SMP from <linux/config.h> and 
defining __SMP__ accordingly before inclusion of any other header
files. I can take care of that.

If anyone wants to compile an SMP-module although the kernel is
configured non-SMP and vice versa, he/she has to edit the Makefile.

Burkhard
-- 
Burkhard Kohl			bu...@bu...