Hello,
There is a compile error if not compiling for SMP:

  gcc -Wp,-MD,arch/ia64/kernel/.mca.o.d -D__KERNEL__ -Iinclude -Wall
-Wstrict-prototypes -Wno-trigraphs -g -O2 -fno-strict-aliasing
-fno-common -pipe  -ffixed-r13 -mfixed-range=f10-f15,f32-f127
-falign-functions=32 -fomit-frame-pointer -nostdinc -iwithprefix include
-mconstant-gp   -DKBUILD_BASENAME=mca -DKBUILD_MODNAME=mca -c -o
arch/ia64/kernel/mca.o arch/ia64/kernel/mca.c
arch/ia64/kernel/mca.c: In function `init_handler_platform':
arch/ia64/kernel/mca.c:347: structure has no member named `write_lock'
arch/ia64/kernel/mca.c:359: structure has no member named `write_lock'
make[1]: *** [arch/ia64/kernel/mca.o] Error 1
make: *** [arch/ia64/kernel] Error 2

It's a bit obvious, in UP tasklist_lock doesn't contain any member :-(
The attached patch let the compilation go. However I don't think it
looks good, there is probably a cleaner way to solve this problem but my
knowledge about the locks is really too little...

Eric