| [487198c] | 1 | Synchronous Programming with User-Level Threads in C∀ | 
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|  | 3 | When computations cannot be satisfied immediately, programmers must use | 
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|  | 4 | one of two paradigms, Synchronous Programming and Asynchronous Programming. | 
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|  | 5 | This presentation discusses the benefits Synchronous Programming over | 
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|  | 6 | Asynchronous Programming and what requirements exist to use this paradigm. | 
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|  | 7 | It also discusses how C∀, a concurrent and backwards-compatible extension | 
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|  | 8 | of the C programming language, has powerful tools available for simple and | 
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|  | 9 | efficient Synchronous Programming. These tools include user-level threads | 
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|  | 10 | and high-level locking mechanisms which simply solve common problems. | 
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|  | 11 | Finally, the presentation shows different techniques to combine these | 
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|  | 12 | features with existing code to either uses blocking operations provided by | 
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|  | 13 | the kernel or is built according to an asynchronous paradigm. | 
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|  | 23 | C∀ is a polymorphic, non-object-oriented, concurrent, backwards-compatible | 
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|  | 24 | extension of the C programming language. This paper discusses the design | 
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|  | 25 | philosophy and implementation of its advanced control-flow and concurrent/parallel | 
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|  | 26 | features, along with the supporting runtime written in C∀. These features | 
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|  | 27 | are created from scratch as ISO C has only low-level and/or unimplemented | 
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|  | 28 | concurrency, so C programmers continue to rely on library features like pthreads. | 
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|  | 29 | C∀ introduces modern language-level control-flow mechanisms, like generators, | 
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|  | 30 | coroutines, user-level threading, and monitors for mutual exclusion and | 
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|  | 31 | synchronization. The runtime provides significant programmer simplification | 
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|  | 32 | and safety by eliminating spurious wakeup and monitor barging. The runtime | 
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|  | 33 | also ensures multiple monitors can be safely acquired simultaneously (deadlock free), | 
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|  | 34 | and this feature is fully integrated with all monitor synchronization mechanisms. | 
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|  | 35 | All control-flow features integrate with the C∀ polymorphic type-system and | 
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|  | 36 | exception handling, while respecting the expectations and style of C programmers. | 
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|  | 37 | Experimental results show comparable performance of the new features with similar | 
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|  | 38 | mechanisms in other concurrent programming languages. | 
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|  | 39 | KEYWORDS | 
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|  | 40 | generator, coroutine, concurrency, parallelism, thread, monitor, runtime, C, C∀ (Cforall) | 
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