Messages in this thread | | | Date | Wed, 29 Mar 2017 11:11:14 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/5] locking: Introduce range reader/writer lock |
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On Mon, Mar 06, 2017 at 09:03:26PM -0800, Davidlohr Bueso wrote: > +/* > + * Implementation of read/write range locks. > + * > + * We keep interval tree of locked and to-be-locked ranges. When new range lock > + * is requested, we add its interval to the tree and store number of intervals > + * intersecting it to 'blocking_ranges'. > + * > + * When a range is unlocked, we again walk intervals that intersect with the > + * unlocked one and decrement their 'blocking_ranges'. We wake up owner of any > + * range lock whose 'blocking_ranges' drops to 0. For the shared case, the > + * 'blocking_ranges' is only incremented if the intersecting range is not marked > + * as a reader.
Not a word about fairness and starvation... Such important topics for lock primitives.
In order to mitigate some of the tree walk overhead for > + * non-intersecting ranges, the tree's min/max values are maintained and consulted > + * in O(1) in the fastpath. > + */
Maybe that ought not be here, doesn't seem like a fundamental design point and would thus be better suited for a comment near where this implementation detail is located ?
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