5.3 Sharing Resources in Multitasking Systems

5.3.1 Problems with Sharing Resources

Up to this point, our example systems have consisted of separate, independent tasks; these perform their functions without any interaction with other tasks. In reality, this situation is rarely met in practical systems; tasks almost always influence each other in some way or means. Let's look at the most common reason for this: task intercommunication, as shown in Figure 5.18:

Figure 5.18: Sharing resources in a multitasking system – example 1

Assume that the design requirement of this pressure control system calls for the control and alarming tasks to exchange and share information. To support such operations, we now include a data store, one that can be written to and read from. Stores like this are frequently formed as records (structs) and/or data arrays, being located in RAM.

Sharing resources in a multitasking system is not, in itself, a problem. What...