INtime® 3.1 Software - tenAsys

Chapter 4: About RT programming
Synchronization
When one thread needs to run before another thread, it can use an exchange object to
signal the second thread when it has completed. For example, the thread that creates
the transaction summary in an automated teller application shouldn’t run until after
the threads that handle withdrawals and deposits run. The transaction summary thread
must synchronize with the other threads.
INtime software provides several objects for synchronization that accommodate a wide
variety of situations. The next figure illustrates using a semaphore to send a signal to
another thread.
Figure 4-6. Threads that use a semaphore for synchronization
A
B
Thread A, the running thread, preprocesses some data. Thread B needs to use the data after thread
A finishes.
When thread A finishes, it sends a signal (not data) to the semaphore.
When thread B receives the signal, it processes the data.
Mutual exclusion
INtime software includes regions that you can use to protect data from being accessed
by multiple threads at the same time. This is called mutual exclusion.
When an INtime application runs, multiple threads can concurrently access the same
data. This is useful in a multithreading system, such as a transaction processing system
where a large number of operators concurrently manipulate a common database.
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