Operating System Concepts Chapter 3

Process Creation

• Parent processes can create child processes, forming a hierarchical tree structure.
• Each process is identified by a unique process identifier (PID).
• Resource sharing between parent and child can vary:
  • All resources shared.
  • Subset of parent’s resources shared.
  • No resources shared.
• Execution strategies involve concurrency or parent waiting for child termination.
• Child processes may duplicate the parent's address space or load a different program.
• In UNIX, the fork() system call generates a new process, while exec() replaces the child's memory space.

Process Termination

• Processes terminate by executing the last statement and invoking exit(), returning status data to the parent via wait().
• Operating systems reclaim resources upon termination.
• Parents can abort child processes if:
  • Resources exceeded or task is no longer needed.
  • Parent is terminating, prohibiting child continuation.
• Some OS enforce child termination upon parent exit.

Multiprocess Architecture

• Single-process browsers may crash due to issues in any single site.
• Google Chrome utilizes a multiprocess model, consisting of:
  • A browser process for UI and I/O management.
  • Renderer processes for rendering web pages per site, operating in sandboxed environments.
  • Separate processes for each browser plug-in.

Interprocess Communication (IPC)

• Processes can be independent or cooperating; cooperating processes interact and share data.
• IPC facilitates:
  • Information sharing.
  • Speeding up computation.
  • Promoting modularity and convenience.
• Two main IPC models:
  • Shared memory.
  • Message passing.

IPC Mechanisms

• Message Passing:

  • Allows processes to communicate and synchronize.
  • Operations include send(message) and receive(message).
  • Message sizes can be fixed or variable.
  • Establishes a communication link between processes for exchanging messages.

• Shared Memory:

  • A shared memory region enables processes to communicate at user-controlled levels.
  • Synchronization mechanisms are needed for concurrent access by multiple processes.

Example IPC System – Windows

• Employs message-passing through Local Procedure Call (LPC) for inter-process communication.
• Communication involves setting up ports as channels for message exchange.
• The client-server communication process includes connection requests and port creation.

Client-Server Communication Models

• Sockets:

  • Serve as endpoints for communication, combining IP addresses and ports.
  • All ports below 1024 are classified as well-known ports.
  • Loopback address is frequently used for local communication.

• Remote Procedure Calls (RPC):

  • Abstract the function call process between networked systems.
  • Involves client-side and server-side stubs for parameter management and execution.

• Pipes:

  • Facilitate communication, with considerations for directionality and process relationship.
  • Ordinary Pipes:
    • Unidirectional, requiring a parent-child relationship; used for standard producer-consumer models.
  • Named Pipes:
    • Bidirectional communication without requiring a parent-child relationship; accessible across processes and platforms.

This quiz focuses on the concepts of process creation and termination in operating systems. It covers how parent processes create child processes and the management of these processes through identifiers. Test your understanding of resource sharing options and the hierarchical nature of process management.