linux-kernel - Re: [PATCH v4 13/15] locking/lockdep: Add support for dynamic keys

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Date:   Fri, 14 Dec 2018 09:20:02 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, tj@...nel.org, longman@...hat.com,
        johannes.berg@...el.com, linux-kernel@...r.kernel.org,
        Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH v4 13/15] locking/lockdep: Add support for dynamic keys

On Tue, 2018-12-11 at 14:13 -0800, Bart Van Assche wrote:
> +/*
> + * Unregister a dynamically allocated key. Must not be called from interrupt
> + * context. The caller must ensure that freeing @key only happens after an RCU
> + * grace period.
> + */
> +void lockdep_unregister_key(struct lock_class_key *key)
> +{
> +	struct hlist_head *hash_head = keyhashentry(key);
> +	struct lock_class_key *k;
> +	struct pending_free *pf;
> +	unsigned long flags;
> +	bool found = false;
> +
> +	might_sleep();
> +
> +	if (WARN_ON_ONCE(static_obj(key)))
> +		return;
> +
> +	pf = get_pending_free_lock(&flags);
> +	if (WARN_ON_ONCE(!pf))
> +		return;
> +	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
> +		if (k == key) {
> +			hlist_del_rcu(&k->hash_entry);
> +			found = true;
> +			break;
> +		}
> +	}
> +	WARN_ON_ONCE(!found);
> +	__lockdep_free_key_range(pf, key, 1);
> +	schedule_free_zapped_classes(pf);
> +	graph_unlock();
> +	raw_local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL_GPL(lockdep_unregister_key);

Since is_dynamic_key() has been modified from using locking into using RCU, a
synchronize_rcu() call needs to be added at the end of lockdep_unregister_key().
I will repost this patch series if the 0-day test infrastructure is happy with
the new version.

Bart.