Interprocess Communication Overview

Interprocess Communication

• Processes can be independent or cooperating.
• Independent processes do not affect each other.
• Cooperating processes can affect each other and share data.

Reasons for Cooperating Processes

• Information sharing: Processes can access shared files concurrently.
• Computation speedup: Parallel execution allows for faster processing on multi-processor systems.
• Modularity: Dividing a system into modules (processes or threads) enhances structure and maintainability.
• Convenience: Users can work on multiple applications simultaneously.

Interprocess Communication (IPC)

• Necessary for cooperating processes to communicate.
• Two main models of IPC:
  • Shared memory: Shared data resides in the memory space of the process that created it.
  • Message passing: Processes exchange messages to communicate.

Communication Models

• Shared Memory:
  • Faster than message passing.
  • Less complex to implement.
  • System calls are only needed for establishing memory regions.
• Message Passing:
  • Easier to implement in distributed systems.
  • Better for exchanging small messages.
  • Requires more system calls, which can be less efficient.

Process Creation

• Parent and child processes can execute concurrently.
• Parent process can wait for the child to terminate using the wait() system call.
• The child process can inherit the parent's address space, allowing for shared data.

Process Creation using UNIX Systems

• The fork() system call creates a new process by duplicating the parent's address space.
• The exec() system call replaces a process's memory space with a new program.
• The wait() system call blocks the parent process until the child process terminates.

Process Termination

• A process can terminate itself using the exit() system call.
• A parent can terminate a child process using the abort() system call.
  • Reasons for termination include resource exhaustion, task completion, or parent termination.
• Orphan processes are child processes whose parent has terminated.

Process Termination (Cont.)

• A child can terminate its parent process using the wait() system call.
• Zombie processes are terminated processes whose parent process has not yet called wait().
• Init/Systemd process handles orphan processes by adopting them and periodically invoking wait().
• This ensures the release of process identifiers and process table entries.

Communication Link

• Links can be physical (e.g., shared memory, hardware bus).
• Links can be logical (e.g., logical properties of the link).
• Communication links enable communication and synchronization between processes.

Direct Communication

• Processes must explicitly name each other during communication.
  • send(P, message) sends a message to process P.
  • receive(Q, message) receives a message from process Q.
• Direct communication links can be:
  • Automatic: Links are established automatically.
  • Unidirectional or Bi-directional: Data flow can be one-way or two-way.
• Each pair of communicating processes has only one link.

Synchronization

• Message passing can be blocking (synchronous) or non-blocking (asynchronous).
• Blocking send: Sender waits until the message is received.
• Blocking receive: Receiver waits until a message is available.
• Non-blocking send: Sender sends the message and continues executing.
• Non-blocking receive: Receiver receives a valid message or null.

Buffering

• Messages reside in a temporary buffer (queue) during communication.
• Buffering can be:
  • Zero capacity: No messages can wait in the queue.
  • Bounded capacity: Limited number of messages allowed in the queue.
  • Unbounded capacity: Infinite number of messages allowed in the queue.

This quiz explores the concepts of interprocess communication (IPC), focusing on independent and cooperating processes. It covers reasons for cooperation, the benefits of shared memory, and message passing models. Test your knowledge on how processes communicate and the advantages of concurrent processing.