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Section 9: Tasks and Synchronization

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The execution of an Ada program consists of the execution of one or more tasks. Each task represents a separate thread of control that proceeds independently and concurrently between the points where it interacts with other tasks. The various forms of task interaction are described in this section, and include:
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In addition, tasks can communicate indirectly by reading and updating (unprotected) shared variables, presuming the access is properly synchronized through some other kind of task interaction.

Static Semantics

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The properties of a task are defined by a corresponding task declaration and task_body, which together define a program unit called a task unit

Dynamic Semantics

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Over time, tasks proceed through various states. A task is initially inactive; upon activation, and prior to its termination it is either blocked (as part of some task interaction) or ready to run. While ready, a task competes for the available execution resources that it requires to run. 
NOTES
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1  Concurrent task execution may be implemented on multicomputers, multiprocessors, or with interleaved execution on a single physical processor. On the other hand, whenever an implementation can determine that the required semantic effects can be achieved when parts of the execution of a given task are performed by different physical processors acting in parallel, it may choose to perform them in this way.

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