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tion between the sender and receiver we are sending a small
OS_Message (the character ‘c’) in these two RTOS.
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In this alternative implementation we are sending the signals using
OS_Send and OS_Receive. Signals are now sent to OS_Message
queues. The sender sends the pointer to the SDL signal in an
OS_Message to the receiver’s OS_Queue. When the signal is received,
the SDL signal is unpacked and linked in to the receivers input queue.
The advantage with this implementation is that there is now synchronization
between the sender and the receiver. Any number of threads can
send signals at the same time to a specific receiver without having to
wait for a semaphore.
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We also provide an alternate run-time model, which is called a Tight integration
because the generated code interacts directly with the underlying
operating system when creating processes, sending signals, etc.
The SDL processes run as separate OS tasks as explained below. Scheduling
is handled by the OS and is normally time-sliced, priority based
and preemptive.
Communication takes place using the inter-process communications
mechanisms offered by the OS, normally message queues. This applies
to signals sent between SDL processes as well as signals sent to or received
from the environment. There are no environment functions, as illustrated
in Figure 560.
July 2003 Telelogic Tau 4.5 User’s Manual ,um-st1