Process Coordination

Process coordination consists of synchronization and mutual exclusion, which were discussed earlier. We will now study different techniques for process coordination. We first make a few definitions related to process coordination.

Critical Section

Instructions that must be executed while another activity is excluded will be called a critical section. For instance in an earlier example we saw that the statement:

A[n++] = item

Consider the following situation: Process p1 is in a critical section c1 waiting for process p2 to get out of a critical section c2. Process p2, meanwhile, is waiting for process p1 to get out of c1. Both p1 and p2 are stuck: each is waiting to get into a critical section being executed by the other. This sort of circular waiting is called a deadlock. In Europe, it is known by the more striking name of ``deadly embrace''.

Another problem related to process coordination is starvation. This problem arises when one or more processes waiting for a critical section are never allowed to enter the region.

Different process coordination techniques are often judged on the basis of their ability to prevent these two problems.

• Disabling Context Switching
• Busy Waiting
• Semaphores
  • Implementation
• Monitors
• Path Expressions
• Synchronous Message Passing