Process Management 1

Process Creation, Process Termination

 

Process Creation

• parent process creats children process
• Tree(Hierarchical structure) formation of processes
• processes require resource
  • Receive resources from the OS
  • share with parents
• share of resources
  1. A model in which parents and children share all resources
  2. A model that shares a part of it
  3. A model that you don't share at all
• Execution
  
  • Parent and child co-existence model
  • Model where the parent waits for the child to terminate
• Address space
  • child copies parent's space(binary and OS data)
  • child putting up a new program in that space
• Exemples of UNIX
  • 'fork()' system call creats new process
    • copy the parent exactly  as it is (OS data except PID + binary)
    • Address space allocation
  • putting up a new program to memory via exec() system call following fork

Process Termination

• The process performe the last command and then notified the OS(exit)
  • The child sends output data to parent (via wait)
  • Various resources in the process are returned to the OS
• The parent process terminates the child process
  • The child exceeds the limit of allocation resources
  • Task assigned to child no longer required
  • When the parent terminates
    
    • The OS does not allow the child to perform any more if the parent process ends
    • Phased termination