printk, lockdep: Disable lock debugging on zap_locks()

zap_locks() is used by printk() in a last ditch effort to get data
out, clearly we cannot trust lock state after this so make it disable
lock debugging.

Also don't treat printk recursion through lockdep as a normal
recursion bug but try hard to get the lockdep splat out.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kqxwmo4xz37e1s8w0xopvr0q@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/printk.c b/kernel/printk.c
index 1455a0d..6d08794 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -688,6 +688,7 @@
 
 	oops_timestamp = jiffies;
 
+	debug_locks_off();
 	/* If a crash is occurring, make sure we can't deadlock */
 	raw_spin_lock_init(&logbuf_lock);
 	/* And make sure that we print immediately */
@@ -856,7 +857,7 @@
 		 * recursion and return - but flag the recursion so that
 		 * it can be printed at the next appropriate moment:
 		 */
-		if (!oops_in_progress) {
+		if (!oops_in_progress && !lockdep_recursing(current)) {
 			recursion_bug = 1;
 			goto out_restore_irqs;
 		}