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Development of real-time scheduling components
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Memory protection in a threaded system
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POSIX signals in threaded environment
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Author(s):
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Alfons Crespo
(UPVLC),
Ismael Ripoll
(UPVLC),
Miguel Masmano
(UPVLC) and
Josep Vidal
(UPVLC).
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Participants:
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Universidad Politecnica de Valencia.
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Description:
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The signal mechanism is the method used in POSIX to deliver asynchronous events to a running process. Signals are similar in concept to a hardware interrupt: when a signal is delivered to a process, the normal flow of the process is interrupted and the signal handler function is called, once the handler function finishes the process continues with its original execution flow. Signals were designed and developed to work in a UNIX heavy process environment, where each process has its own protected memory space, its priority (or round-robing quantum), a single process state, etc. In this execution environment, every process has its own set of signals handlers and blocking mask. In a system where the execution entities are not processes but threads that share most of their state, the original definition (and operation) of signals is no longer valid. The POSIX standard has tried to extend the signal semantic for threads. The authors of this paper believe that the standard can be improved. A better combination of signals and threads can be defined.
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Keywords:
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POSIX threads, POSIX signals, Real-Time Linux
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[more ...]
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