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

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Message-ID: <20170329151447.GF27446@linux-80c1.suse>
Date:   Wed, 29 Mar 2017 08:14:47 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, akpm@...ux-foundation.org, jack@...e.cz,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/5] locking: Introduce range reader/writer lock

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.