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SIG34-EX1: On a machine with persistent signal handlers, it is safe for a handler to modify the behavior for its own signal. This would include having the signal be ignored, reset to default behavior, or handled by a different handler. A handler assigning itself to its own signal is also safe, as it is a no-op. The handler is impervious to a race condition because Since multiple invocations of its signal will merely cause it to "interrupt itself", the handler is impervious to a race condition until it manages to reassign its signal.
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