Kernel lock exclusion is actually needed in the boot sequence,

so we need to make init_idle() aware of it so that it gets the
preempt_count initialization right.

init/main.c

@@ -338,6 +338,7 @@ asmlinkage void __init start_kernel(void)
  * Interrupts are still disabled. Do necessary setups, then
  * enable them
  */
+	lock_kernel();
 	printk(linux_banner);
 	setup_arch(&command_line);
 	setup_per_cpu_areas();
@@ -405,8 +406,6 @@ asmlinkage void __init start_kernel(void)
 
 	init_idle(current, smp_processor_id());
 
-	lock_kernel();
-
 	/* 
 	 *	We count on the initial thread going ok 
 	 *	Like idlers init is an unlocked kernel thread, which will

kernel/sched.c

@@ -1438,7 +1438,7 @@ void __init init_idle(task_t *idle, int cpu)
 	idle->prio = MAX_PRIO;
 	idle->state = TASK_RUNNING;
 	idle->thread_info->cpu = cpu;
-	idle->thread_info->preempt_count = 0;
+	idle->thread_info->preempt_count = (idle->lock_depth >= 0);
 	double_rq_unlock(idle_rq, rq);
 	set_tsk_need_resched(idle);
 	__restore_flags(flags);