Sorry, hunk with corresponding preempt_enable was lost, sending patch again.

This patch fixes deadlock of stop_machine() vs. synchronous IPI send.
The problem is that stop_machine() disables interrupts before disabling 
preemption on other CPUs. So if another CPU is preempted and then calls 
something like flush_tlb_all() it will deadlock with CPU doing 
stop_machine() and which can't process IPI due to disabled IRQs.

I changed stop_machine() to do the same things exactly as it does on 
other CPUs, i.e. it should disable preemption first on _all_ CPUs 
including itself and only after that disable IRQs.

Signed-Off-By: Kirill Korotaev <dev@sw.ru>

Kirill