[PATCH] cpu_idle() startup race fix

Diagnosis from Christian Vogel <vogel@skunk.physik.uni-erlangen.de>

cpu_idle() tests pm_idle() just once then falls into the

	while (!need_resched())
		idle();

loop.

Problem is, that loop never terminates (need_resched() always returns false
on preemptive kernels).

The other problem is that ACPI updates pm_idle _after_ cpu_idle() has taken a
local copy.  So we always call default_idle(), even when pm_idle is pointing
at a new idle handler.

So fix it to pick up changed values of pm_idle() each time around the inner
loop.

arch/i386/kernel/process.c

@@ -138,12 +138,15 @@ void cpu_idle (void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
-		void (*idle)(void) = pm_idle;
-		if (!idle)
-			idle = default_idle;
-		irq_stat[smp_processor_id()].idle_timestamp = jiffies;
-		while (!need_resched())
+		while (!need_resched()) {
+			void (*idle)(void) = pm_idle;
+
+			if (!idle)
+				idle = default_idle;
+
+			irq_stat[smp_processor_id()].idle_timestamp = jiffies;
 			idle();
+		}
 		schedule();
 	}
 }