x86: add C1E aware idle function, fix

On Tue, 17 Jun 2008, Rafael J. Wysocki wrote:
>
> BTW, with the C1E patches reverted I don't get the
> WARNING: at /home/rafael/src/linux-next/kernel/smp.c:215 smp_call_function_single+0x3d/0xa2
> in the log.  Thomas?

The BROADCAST_FORCE notification uses smp_function_call and therefor
must be run with interrupts enabled.

While at it, add a comment for the BROADCAST_EXIT notifier as well.

Reported-and-bisected-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>