locking, printk: Annotate logbuf_lock as raw

The logbuf_lock lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ merged and fixed it ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 027a03f..c96d500 100644
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -39,7 +39,7 @@
 	 * in addition to the one that will be printed by
 	 * the entity that is holding the lock already:
 	 */
-	if (!spin_trylock_irqsave(&rs->lock, flags))
+	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
 		return 0;
 
 	if (!rs->begin)
@@ -60,7 +60,7 @@
 		rs->missed++;
 		ret = 0;
 	}
-	spin_unlock_irqrestore(&rs->lock, flags);
+	raw_spin_unlock_irqrestore(&rs->lock, flags);
 
 	return ret;
 }