Title
Proving Highly-Concurrent Traversals Correct
Abstract
Modern highly-concurrent search data structures, such as search trees, obtain multi-core scalability and performance by having operations traverse the data structure without any synchronization. As a result, however, these algorithms are notoriously difficult to prove linearizable, which requires identifying a point in time in which the traversal's result is correct. The problem is that traversing the data structure as it undergoes modifications leads to complex behaviors, necessitating intricate reasoning about all interleavings of reads by traversals and writes mutating the data structure. In this paper, we present a general proof technique for proving unsynchronized traversals correct in a significantly simpler manner, compared to typical concurrent reasoning and prior proof techniques. Our framework relies only on sequential properties of traversals and on a conceptually simple and widely-applicable condition about the ways an algorithm's writes mutate the data structure. Establishing that a target data structure satisfies our condition requires only simple concurrent reasoning, without considering interactions of writes and reads. This reasoning can be further simplified by using our framework. To demonstrate our technique, we apply it to prove several interesting and challenging concurrent binary search trees: the logical-ordering AVL tree, the Citrus tree, and the full contention-friendly tree. Both the logical-ordering tree and the full contention-friendly tree are beyond the reach of previous approaches targeted at simplifying linearizability proofs.
Year
DOI
Venue
2020
10.1145/3428196
Proceedings of the ACM on Programming Languages
Keywords
DocType
Volume
concurrent data structures,linearizability,proof framework,traversal,traversal correctness
Journal
4
Issue
ISSN
Citations 
OOPSLA
2475-1421
0
PageRank 
References 
Authors
0.34
0
7
Name
Order
Citations
PageRank
Yotam M. Y. Feldman163.10
Artem Khyzha2242.85
Constantin Enea324926.95
Adam Morrison425421.37
Aleksandar Nanevski558327.01
Noam Rinetzky642130.69
Sharon Shoham734226.67