On Mon, 2006-11-20 at 23:02 +0100, Ingo Molnar wrote:
>   http://redhat.com/~mingo/realtime-preempt/patch-2.6.19-rc6-rt5

if I don't put in .config 
CONFIG_HOTPLUG_CPU=y

I got  
UPD     include/linux/compile.h
arch/x86_64/kernel/vsyscall.c: In function 'vsyscall_init':
arch/x86_64/kernel/vsyscall.c:334: error: 'cpu_vsyscall_notifier' undeclared (first use in this function)
arch/x86_64/kernel/vsyscall.c:334: error: (Each undeclared identifier is reported only once
arch/x86_64/kernel/vsyscall.c:334: error: for each function it appears in.)
make[1]: *** [arch/x86_64/kernel/vsyscall.o] Error 1

Now with CONFIG_HOTPLUG_CPU=y I got:
  UPD     include/linux/compile.h
kernel/fork.c:72: error: section of 'tasklist_lock' conflicts with previous declaration
make[1]: *** [kernel/fork.o] Error 1
make: *** [kernel] Error 2
error: Bad exit status from /var/tmp/rpm-tmp.64648 (%build)

Other curious thing now I have a way to reproduce an hang on my system
is build kernel with -j165 for build parallelism

Just in case send my .config in attach:

Thanks,
-- 
Sérgio M.B.