Symmetry-Aware Predicate Abstraction for Shared-Variable Concurrent Programs

<p>This thesis explores two kinds of program logics that have become important for modern program verification - separation logic, for reasoning about programs that use pointers to build mutable data structures, and rely guarantee reasoning, for reasoning about shared variable concurrent programs. We look more closely into the motivations for merging these two kinds of logics into a single formalism that exploits the benefits of both approaches - local, modular, and explicit reasoning about interference between threads in a shared memory concurrent program. We discuss in detail two such formalisms - RGSep and Local Rely Guarantee (LRG), in particular we analyse how each formalism models program state and treats the distinction between global state (shared by all threads) and local state (private to a given thread) and how each logic models actions performed by threads on shared state, and look into the proof rules specifically for reasoning about atomic blocks of code. We present full examples of proofs in each logic and discuss their differences. This thesis also illustrates how a weakest precondition semantics for separation logic can be used to carry out calculational proofs. We also note how in essence these proofs are data abstraction proofs showing that a data structure implements some abstract data type, and relate this idea to a classic data abstraction technique by Hoare. Finally, as part of the thesis we also present a survey of tools that are currently available for doing manual or semi-automated proofs as well as program analyses with separation logic and rely guarantee.</p>

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Program Verification with Separation Logic and Rely Guarantee

10.26686/wgtn.17060108.v1 ◽

2021 ◽

Author(s):

◽

Allan Tabilog

Keyword(s):

Program Verification ◽

Separation Logic ◽

Concurrent Programs ◽

Abstract Data Type ◽

Data Abstraction ◽

Global State ◽

Shared Variable ◽

Concurrent Program ◽

Abstract Data ◽

Shared State

<p>This thesis explores two kinds of program logics that have become important for modern program verification - separation logic, for reasoning about programs that use pointers to build mutable data structures, and rely guarantee reasoning, for reasoning about shared variable concurrent programs. We look more closely into the motivations for merging these two kinds of logics into a single formalism that exploits the benefits of both approaches - local, modular, and explicit reasoning about interference between threads in a shared memory concurrent program. We discuss in detail two such formalisms - RGSep and Local Rely Guarantee (LRG), in particular we analyse how each formalism models program state and treats the distinction between global state (shared by all threads) and local state (private to a given thread) and how each logic models actions performed by threads on shared state, and look into the proof rules specifically for reasoning about atomic blocks of code. We present full examples of proofs in each logic and discuss their differences. This thesis also illustrates how a weakest precondition semantics for separation logic can be used to carry out calculational proofs. We also note how in essence these proofs are data abstraction proofs showing that a data structure implements some abstract data type, and relate this idea to a classic data abstraction technique by Hoare. Finally, as part of the thesis we also present a survey of tools that are currently available for doing manual or semi-automated proofs as well as program analyses with separation logic and rely guarantee.</p>

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Delay-Bounded Scheduling Without Delay!

Computer Aided Verification - Lecture Notes in Computer Science ◽

10.1007/978-3-030-81685-8_18 ◽

2021 ◽

pp. 380-402

Author(s):

Andrew Johnson ◽

Thomas Wahl

Keyword(s):

Predicate Abstraction ◽

Finite Domain ◽

Concurrent Programs ◽

Prior Work ◽

Safety Properties ◽

Bug Detection ◽

Delay Bound ◽

Deterministic Scheduling ◽

Variable Domains ◽

Bug Finding

AbstractWe consider the broad problem of analyzing safety properties of asynchronous concurrent programs under arbitrary thread interleavings. Delay-bounded deterministic scheduling, introduced in prior work, is an efficient bug-finding technique to curb the large cost associated with full scheduling nondeterminism. In this paper we first present a technique to lift the delay bound for the case of finite-domain variable programs, thus adding to the efficiency of bug detection the ability to prove safety of programs under arbitrary thread interleavings. Second, we demonstrate how, combined with predicate abstraction, our technique can both refute and verify safety properties of programs with unbounded variable domains, even for unbounded thread counts. Previous work has established that, for non-trivial concurrency routines, predicate abstraction induces a highly complex abstract program semantics. Our technique, however, never statically constructs an abstract parametric program; it only requires some abstract-states set to be closed under certain actions, thus eliminating the dependence on the existence of verification algorithms for abstract programs. We demonstrate the efficiency of our technique on many examples used in prior work, and showcase its simplicity compared to earlier approaches on the unbounded-thread Ticket Lock protocol.

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