linux-kernel - [PATCH] lockdep: debug_show_all_locks & debug_show_held_locks vs. debug

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Message-ID: <20070322065759.GB1466@ff.dom.local>
Date:	Thu, 22 Mar 2007 07:57:59 +0100
From:	Jarek Poplawski <jarkao2@...pl>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Neil Brown <neilb@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Folkert van Heusden <folkert@...heusden.com>,
	linux-kernel@...r.kernel.org,
	"J\. Bruce Fields" <bfields@...ldses.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] lockdep: debug_show_all_locks &  debug_show_held_locks vs. debug_locks


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@...heusden.com>
Inspired-by: Oleg Nesterov <oleg@...sign.ru>
Signed-off-by: Jarek Poplawski <jarkao2@...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);
 }
 
-
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