Examples of communication safety

Asynchronous Library Calls 1

• The following shows the correct sequence of communication operations

Asynchronous Library Calls 2

• The following shows an incorrect sequence of communication operations

• Deadlock results in this case.
• Need to differentiate between messages sent in library routine and rest of application.

Synchronous Library Calls 1

• In this case the library call is made synchronously.
• Still have problems if there are communication operations outstanding on entry.
• Intended behavior:

Synchronous Library Calls 2

• Possible behavior:

  

• Again we must separate communication operations inside the library from those in the rest of the application.