handle recursive calls to bust_spinlocks()

Various architectures may call bust_spinlocks() recursively; the function
itself, however, doesn't appear to be meant to be called in this manner.
Nevertheless, this doesn't appear to be a problem as long as
bust_spinlocks(0) doesn't get called twice in a row (otherwise,
unblank_screen() may enter the scheduler).  However, at least on i386 die()
has been capable of returning (and on other architectures this should
really be that way, too) when notify_die() returns NOTIFY_STOP.

Short of getting a reply to a respective query, this patch makes
bust_spinlocks() increment/decrement oops_in_progress, and wake klogd only
when the count drops back to zero.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/bust_spinlocks.c

@@ -17,12 +17,12 @@
 void __attribute__((weak)) bust_spinlocks(int yes)
 {
 	if (yes) {
-		oops_in_progress = 1;
+		++oops_in_progress;
 	} else {
 #ifdef CONFIG_VT
 		unblank_screen();
 #endif
-		oops_in_progress = 0;
+		if (--oops_in_progress == 0)
 			wake_up_klogd();
 	}
 }