Quiescent Consistency: Defining and Verifying Relaxed Linearizability

Derrick, John; Dongol, Brijesh; Schellhorn, Gerhard; Tofan, Bogdan; Travkin, Oleg; Wehrheim, Heike

doi:10.1007/978-3-319-06410-9_15

Cited by 14 publications

(37 citation statements)

References 22 publications

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“…The notion of quiescent consistency we have considered is based on the definition by Derrick et al [11], which is a formalisation of Shavit's definition [35]. This definition allows operation calls by the same process to be reordered, i.e., sequential consistency [31] is not necessarily preserved.…”

Section: Discussionmentioning

confidence: 99%

“…The queue only satisfies quiescent consistency if Deq is blocking, i.e., waits until an element is found in the queue. The diffracting queue is not quiescent consistent if Deq returns on empty (see [11] for details). Figure 2.…”

Section: A Quiescent Consistent Queuementioning

confidence: 99%

“…History h1 is not linearizable [24] because the dequeues by processes 4 and 5 violate the FIFO order of enqueues by processes 2 and 3, and linearizability does not allow non-overlapping operations to be reordered (see [11] for details). However, h1 is quiescent consistent because quiescent consistency allows operations between two consecutive quiescent states to be reordered even if they do not overlap.…”

Section: A Quiescent Consistent Queuementioning

confidence: 99%

“…A concurrent object satisfies C iff each of its histories is correct with respect to C. These two notions give rise to two distinct verification problems: the former gives rise to a membership problem, and the latter a correctness problem. In this paper, we study the decidability and complexity of both membership and correctness for systems in which the condition C above is quiescent consistency [11,35].…”

Section: Introductionmentioning

confidence: 99%

“…Quiescent consistency allows events of a concurrent object's history between two consecutive quiescent states to be reordered (when mapping to a sequential history) but disallows reorderings for events separated by a quiescent state [11,15,35]. For both membership and correctness, we consider two versions of the problem: an unrestricted version with no limits between two quiescent states and a restricted version that assumes a fixed upper bound on the number of events between two quiescent states.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Decidability and Complexity for Quiescent Consistency

Dongol

Hierons

2016

Proceedings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science

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Quiescent consistency is a notion of correctness for a concurrent object that gives meaning to the object's behaviours in quiescent states, i.e., states in which none of the object's operations are being executed. The condition enables greater flexibility in object design by allowing more behaviours to be admitted, which in turn allows the algorithms implementing quiescent consistent objects to be more efficient (when executed in a multithreaded environment).Quiescent consistency of an implementation object is defined in terms of a corresponding abstract specification. This gives rise to two important verification questions: membership (checking whether a behaviour of the implementation is allowed by the specification) and correctness (checking whether all behaviours of the implementation are allowed by the specification). In this paper, we consider the membership and correctness conditions for quiescent consistency, as well as a restricted form that assumes an upper limit on the number of events between two quiescent states. We show that the membership problem for unrestricted quiescent consistency is NP-complete and that the correctness problem is decidable, coNEXPTIME-hard, and in EXPSPACE. For the restricted form, we show that membership is in PTIME, while correctness is PSPACE-complete.

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Section: Discussionmentioning

confidence: 99%

Section: A Quiescent Consistent Queuementioning

confidence: 99%

Section: A Quiescent Consistent Queuementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Decidability and Complexity for Quiescent Consistency

Dongol

Hierons

2016

Proceedings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science

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Verifying Visibility-Based Weak Consistency

Krishna

Emmi

Enea

et al. 2020

Programming Languages and Systems

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Multithreaded programs generally leverage e cient and thread-safe concurrent objects like sets, key-value maps, and queues. While some concurrentobject operations are designed to behave atomically, each witnessing the atomic e ects of predecessors in a linearization order, others forego such strong consistency to avoid complex control and synchronization bottlenecks. For example, contains (value) methods of key-value maps may iterate through key-value entries without blocking concurrent updates, to avoid unwanted performance bottlenecks, and consequently overlook the e ects of some linearization-order predecessors. While such weakly-consistent operations may not be atomic, they still o er guarantees, e.g., only observing values that have been present. In this work we develop a methodology for proving that concurrent object implementations adhere to weak-consistency speci cations. In particular, we consider (forward) simulation-based proofs of implementations against relaxedvisibility speci cations, which allow designated operations to overlook some of their linearization-order predecessors, i.e., behaving as if they never occurred. Besides annotating implementation code to identify linearization points, i.e., points at which operations' logical e ects occur, we also annotate code to identify visible operations, i.e., operations whose e ects are observed; in practice this annotation can be done automatically by tracking the writers to each accessed memory location. We formalize our methodology over a general notion of transition systems, agnostic to any particular programming language or memory model, and demonstrate its application, using automated theorem provers, by verifying models of Java concurrent object implementations.

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On the Correctness Problem for Serializability

König

Wehrheim

2021

Theoretical Aspects of Computing – ICTAC 2021

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Quiescent Consistency: Defining and Verifying Relaxed Linearizability

Cited by 14 publications

References 22 publications

Decidability and Complexity for Quiescent Consistency

Decidability and Complexity for Quiescent Consistency

Verifying Visibility-Based Weak Consistency

On the Correctness Problem for Serializability

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