SMP module compilation on UP?

Hi,

Is it possible to build an SMP module on a machine running a UP kernel (or vice versa)? We of course get unresolved symbols during module load due to the smp prefix on the ksyms, and haven't seen how to get around it. (Defining __SMP__ does not cut it, though I believe this used to work a while ago).

Please reply to me as well as to the list.

Thanks,
-mark

Yes. It does not matter what kernel you are running. What's important is that you configure your sources. Configure your kernel for SMP and do a 'make dep', then compile your module.

     Rafael

Is this the only way - to keep two separately configured kernel source trees? No way to do it via some flag?

thanks,
-mark

With 2.4, yes. You need a complete set of kernel source for every set of config files you use because the object code is written to the source directory. With 2.5 you can have a single source tree and multiple object trees, one for each config that you are working on.

In either case you must keep separate sets of objects for each config, mixing objects from different configs in a single tree is a recipe for disaster.

Use cp -al to replicate your kernel source tree before configuring. It creates a tree with hard links, so you don't waste disk space. Just don't forget to unlink() the files, if you edit them manually. (*)

garloff@garloff:~/Physics/numerix $ type unlink
unlink is a function
unlink ()

{ 
    for name in $*;
    do
	test -f $name && { 
	    mv $name $name~$PPID;
	    cp -pd $name~$PPID $name;
	    rm $name~$PPID
	};
    done
}

(*) If you use emacs, you don't need to unlink before edit. The backup file
will stay linked, but the edited is unique. patch does unlink, so patching is no problem. vi does NOT unlink.

Regards,

Kurt Garloff  <[email protected]>                          Eindhoven, NL
GPG key: See mail header, key servers         Linux kernel development
SuSE GmbH, Nuernberg, FRG                               SCSI, Security

Build - yes. Load - no. Not unless you like your kernel exploding into a million tiny pieces. You can compile anything from anywhere, you can even compile the kernel from other operating systems. But loading an SMP module into a UP system or vice versa guarantees data mismatches.

Why not just run an SMP kernel on UP machine? Yes, there may be minor performance penalty but that may be irrelevant for you if it lets you build and load SMP modules on that machine. With a UP kernel running, you will be able to build SMP modules but not load them.

Khalid

====================================================================
Khalid Aziz                             Linux Development Laboratory
(970)898-9214                                        Hewlett-Packard
[email protected]                                    Fort Collins, CO