Logical Concurrency Control From Sequential Proofs

In this paper, we consider the problem of making a sequential library

safe for concurrent clients. Informally, given a sequential library that

works satisfactorily when invoked by a sequential client, we wish to

synthesize concurrency control code for the library that ensures that

it will work satisfactorily even when invoked by a concurrent client

(which may lead to overlapping executions of the library's procedures).

Formally, we consdier a sequential library annotated with

assertions along with a proof that these assertions hold in a sequential

execution. We show how such a proof can be used to derive a

concurrency control for the library that guarantees that the library's

execution will satisfy the same assertions even when invoked by a

concurrent client. Secondly, we generalize this result by considering

2-state assertions that correspond to relations over a pair of program

states. Such assertions can be used (as postconditions) to specify the

desired functionality of procedures. Thus, the synthesized concurrency

control ensures that procedures have the desired functionality

even in a concurrent setting. Finally, we extend the approach to

guarantee linearizability: any concurrent execution of a procedure

is not only guaranteed to satisfy its specification, it also appears to

take effect instantaneously at some point during its execution. A notable

feature of our solution is that it is based on a logical notion of

interference between threads: the derived concurrency control prevents

threads from violating properties (by executing statements)

that are to be preserved at a given program point, rather than preventing

threads from accessing/modifying specific data.

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Publisher  Association for Computing Machinery, Inc.
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