[PATCH] Fix early __might_sleep() calls

From: Roger Luethi <rl@hellgate.ch>

__might_sleep prints warnings only after jiffies wrap (typically after 5
minutes of uptime).

kernel/sched.c

@@ -2849,7 +2849,7 @@ void __might_sleep(char *file, int line)
 	static unsigned long prev_jiffy;	/* ratelimiting */
 
 	if (in_atomic() || irqs_disabled()) {
-		if (time_before(jiffies, prev_jiffy + HZ))
+		if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
 			return;
 		prev_jiffy = jiffies;
 		printk(KERN_ERR "Debug: sleeping function called from invalid"