Re: [PATCH] lockdep: debug_show_all_locks & debug_show_held_locks vs. debug_locks

Peter Zijlstra
2007-03-22T07:23:25Z

On Thu, 2007-03-22 at 07:57 +0100, Jarek Poplawski wrote:
> 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>

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

> ---
>
> 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);
> }
>