Re: [tip: locking/core] lockdep: Fix usage_traceoverflow

Peter Zijlstra
2020-10-27T12:48:49Z

On Tue, Oct 27, 2020 at 01:30:56PM +0100, Peter Zijlstra wrote:
> This seems to make it happy. Not quite sure that's the best solution.
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 3e99dfef8408..81295bc760fe 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -4411,7 +4405,9 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
> break;
>
> case LOCK_USED:
> - debug_atomic_dec(nr_unused_locks);
> + case LOCK_USED_READ:
> + if ((hlock_class(this)->usage_mask & (LOCKF_USED|LOCKF_USED_READ)) == new_mask)
> + debug_atomic_dec(nr_unused_locks);
> break;
>
> default:

This also works, and I think I likes it better.. anyone?

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 3e99dfef8408..e603e86c0227 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4396,6 +4390,9 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
if (unlikely(hlock_class(this)->usage_mask & new_mask))
goto unlock;

+ if (!hlock_class(this)->usage_mask)
+ debug_atomic_dec(nr_unused_locks);
+
hlock_class(this)->usage_mask |= new_mask;

if (new_bit < LOCK_TRACE_STATES) {
@@ -4403,19 +4400,10 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
return 0;
}

- switch (new_bit) {
- case 0 ... LOCK_USED-1:
+ if (new_bit < LOCK_USED) {
ret = mark_lock_irq(curr, this, new_bit);
if (!ret)
return 0;
- break;
-
- case LOCK_USED:
- debug_atomic_dec(nr_unused_locks);
- break;
-
- default:
- break;
}