Operations on Processes

The System must provide mechanisms for:

• process creation

• process termination

Process Creation

Parent process create Children processes, which may make more of their own, creating a Tree

Each Process has a Process Identifier (PID)

Resource Sharing Options:

• Parent and children share all resources

• Children share subset of parent’s resources

• Parent and child share no resources

Execution Options:

• Parent and children execute concurrently

• Parent waits until children terminate

A Child is ether:

• duplicate of the parents

• has a program loaded into it

fork() - system call creates a new process

exec() - replaces the processes memory space with a new process

wait() - parent process calls wait() while waiting for the child process to terminate

exit() - deletes child process, returns status data to wait command, resources are dealocated

Process Termination

1. Process is deleted

2. Resources are realocated

abort() - used when parent wants to stop child process

Reasons include:

• Child exceeded allocated resources

• Task assigned to child process no longer needed

• Parent is being terminated and therefore child processes are closed (cascading termination)

Zombie - there is no parent waiting

Orphan - parent process terminated without using wait()

Example of multiprocess architecture