Re: [PATCH 1/5] locking: Introduce range reader/writer lock

[Davidlohr Bueso]

On Wed, 29 Mar 2017, Peter Zijlstra wrote:

> On Mon, Mar 06, 2017 at 09:03:26PM -0800, Davidlohr Bueso wrote:
> > +static __always_inline int
> > +__range_read_lock_common(struct range_rwlock_tree *tree,
> > +			 struct range_rwlock *lock, long state)
> > +{
> > +	struct interval_tree_node *node;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&tree->lock, flags);
> > +	lock->reader = true;
> > +
> > +	if (!__range_intersects_intree(tree, lock))
> > +		goto insert;
> > +
> > +	node = interval_tree_iter_first(&tree->root, lock->node.start,
> > +					 lock->node.last);
> > +	while (node) {
> > +		struct range_rwlock *blocked_lock;
> > +		blocked_lock = range_entry(node, struct range_rwlock, node);
> > +
> > +		if (!blocked_lock->reader)
> > +			lock->blocking_ranges++;
> > +		node = interval_tree_iter_next(node, lock->node.start,
> > +					       lock->node.last);
> > +	}
> > +insert:
> > +	__range_tree_insert(tree, lock);
> > +
> > +	lock->task = current;
> > +	spin_unlock_irqrestore(&tree->lock, flags);
> > +
> > +	return wait_for_ranges(tree, lock, state);
> > +}
>
> Another thing; this implementation lacks lockdep annotations and has 0
> other debugging features.

True.

> Is there something that makes the normal rwsem lockdep annotation not
> work for this?

Not that I know of. Let me look into it.