Re: [PATCH v7 18/23] locking/lockdep: Add support for dynamic keys

[Peter Zijlstra]

On Thu, Feb 14, 2019 at 03:00:53PM -0800, Bart Van Assche wrote:
> +/* hash_entry is used to keep track of dynamically allocated keys. */
>  struct lock_class_key {
> +	struct hlist_node		hash_entry;
>  	struct lockdep_subclass_key	subkeys[MAX_LOCKDEP_SUBCLASSES];
>  };

I think we can make that:

struct lock_class_key {
	union {
		struct hlist_node		hash_entry;
		struct lockdep_subclass_key	subkeys[MAX_LOCKDEP_SUBCLASSES];
	};
};

I've added a patch to that effect at the end. IIRC we never actually
store anything in the subkeys, we just use the address.