Synchronising C/C++ and POWER

Sarkar, Susmit and Memarian, Kayvan and Owens, Scott and Batty, Mark and Sewell, Peter and Maranget, Luc and Alglave, Jade and Williams, Derek (2012) Synchronising C/C++ and POWER. In: PLDI '12: 33rd ACM SIGPLAN Conference on Programming Language Design and Implementation, 11th-16th June, 2012, Beijing, china. (The full text of this publication is not available from this repository)

The full text of this publication is not available from this repository. (Contact us about this Publication)
Official URL
http://dx.doi.org/10.1145/2254064.2254102

Abstract

Shared memory concurrency relies on synchronisation primitives: compare-and-swap, load-reserve/store-conditional (aka LL/SC), language-level mutexes, and so on. In a sequentially consistent setting, or even in the TSO setting of x86 and Sparc, these have well-understood semantics. But in the very relaxed settings of IBM®, POWER®, ARM, or C/C++, it remains surprisingly unclear exactly what the programmer can depend on. This paper studies relaxed-memory synchronisation. On the hardware side, we give a clear semantic characterisation of the load-reserve/store-conditional primitives as provided by POWER multiprocessors, for the first time since they were introduced 20 years ago; we cover their interaction with relaxed loads, stores, barriers, and dependencies. Our model, while not officially sanctioned by the vendor, is validated by extensive testing, comparing actual implementation behaviour against an oracle generated from the model, and by detailed discussion with IBM staff. We believe the ARM semantics to be similar. On the software side, we prove sound a proposed compilation scheme of the C/C++ synchronisation constructs to POWER, including C/C++ spinlock mutexes, fences, and read-modify-write operations, together with the simpler atomic operations for which soundness is already known from our previous work; this is a first step in verifying concurrent algorithms that use load-reserve/store-conditional with respect to a realistic semantics. We also build confidence in the C/C++ model in its own terms, fixing some omissions and contributing to the C standards committee adoption of the C++11 concurrency model.

Item Type: Conference or workshop item (Paper)
Subjects: Q Science > QA Mathematics (inc Computing science) > QA 76 Software, computer programming,
Divisions: Faculties > Science Technology and Medical Studies > School of Computing > Programming Languages and Systems Group
Depositing User: Scott Owens
Date Deposited: 24 Oct 2012 10:04
Last Modified: 18 Mar 2013 14:05
Resource URI: http://kar.kent.ac.uk/id/eprint/31892 (The current URI for this page, for reference purposes)
  • Depositors only (login required):