* Bart Van Assche <bvanass...@acm.org> wrote:
> If lockdep_register_key() and lockdep_unregister_key() are called with
> debug_locks == false then the following warning is reported:
>
> WARNING: CPU: 2 PID: 15145 at kernel/locking/lockdep.c:4920
> lockdep_unregister_key+0x1ad/0x240
>
> That warning is reported because lockdep_unregister_key() ignores the
> value of 'debug_locks' and because the behavior of lockdep_register_key()
> depends on whether or not 'debug_locks' is set. Fix this inconsistency
> by making lockdep_register_key() unconditionally register lock keys.
>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Will Deacon <will.dea...@arm.com>
> Cc: Waiman Long <long...@redhat.com>
> Cc: shenghui <shh...@foxmail.com>
> Reported-by: shenghui <shh...@foxmail.com>
> Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer
> in use") # v5.1-rc1.
> Signed-off-by: Bart Van Assche <bvanass...@acm.org>
> ---
> kernel/locking/lockdep.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index d2d65bbfae01..a228509b62f1 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -1027,15 +1027,16 @@ void lockdep_register_key(struct lock_class_key *key)
> hash_head = keyhashentry(key);
>
> raw_local_irq_save(flags);
> - if (!graph_lock())
> - goto restore_irqs;
> + arch_spin_lock(&lockdep_lock);
> + current->lockdep_recursion = 1;
> hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
> if (WARN_ON_ONCE(k == key))
> goto out_unlock;
> }
> hlist_add_head_rcu(&key->hash_entry, hash_head);
> out_unlock:
> - graph_unlock();
> + current->lockdep_recursion = 0;
> + arch_spin_unlock(&lockdep_lock);
> restore_irqs:
> raw_local_irq_restore(flags);
> }
So why don't we add a debug_locks test to lockdep_unregister_key()
instead? The general principle to bring lockdep to a screeching halt when
bugs are detected, ASAP.
Thanks,
Ingo
