[PATCH] lockdep: debug_show_all_locks & debug_show_held_locks vs. debug_locks

[Jarek Poplawski <jarkao2@o2.pl>]

And here is some addition.

[PATCH] lockdep: debug_show_all_locks &  debug_show_held_locks vs. debug_locks
 
lockdep's data shouldn't be used when debug_locks == 0
because it's not updated after this, so it's more misleading
than helpful.

PS: probably lockdep's current-> fields should be reset after
it turns debug_locks off: so, after printing a bug report, but
before return from exported functions, but there are really
a lot of these possibilities (e.g. after DEBUG_LOCKS_WARN_ON),
so, something could be missed. (Of course direct use of this
fields isn't recommended either.)

Reported-by: Folkert van Heusden <folkert@vanheusden.com>
Inspired-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>

---

diff -Nurp 2.6.21-rc4-git4-/kernel/lockdep.c 2.6.21-rc4-git4/kernel/lockdep.c
--- 2.6.21-rc4-git4-/kernel/lockdep.c	2007-03-21 22:46:26.000000000 +0100
+++ 2.6.21-rc4-git4/kernel/lockdep.c	2007-03-21 23:05:17.000000000 +0100
@@ -2742,6 +2742,10 @@ void debug_show_all_locks(void)
 	int count = 10;
 	int unlock = 1;
 
+	if (unlikely(!debug_locks)) {
+		printk("INFO: lockdep is turned off.\n");
+		return;
+	}
 	printk("\nShowing all locks held in the system:\n");
 
 	/*
@@ -2785,6 +2789,10 @@ EXPORT_SYMBOL_GPL(debug_show_all_locks);
 
 void debug_show_held_locks(struct task_struct *task)
 {
+	if (unlikely(!debug_locks)) {
+		printk("INFO: lockdep is turned off.\n");
+		return;
+	}
 	lockdep_print_held_locks(task);
 }