Interprocess Communication in Operating Systems

Chapter 3: Processes

• Processes in an operating system are represented and scheduled in various ways.
• Processes are created and terminated using system calls.
• Processes can communicate through Interprocess Communication (IPC).
• Two models of IPC are: shared memory and message passing.
• The Producer-Consumer problem demonstrates cooperating processes.
• Two variations of the producer-consumer problem are unbounded-buffer and bounded-buffer.
• In shared memory, processes access a dynamically allocated shared memory block.
• In message passing, processes send messages to each other.
• A race condition occurs when multiple processes access and modify shared data concurrently.
• Solutions for avoiding race conditions in shared memory systems exist.
• IPC methods exist as a message passing capability..
• Communication links can be established in various ways: direct and indirect communication methods
• Direct communication links are associated with only one pair, while indirect communication links use mailboxes or ports.

IPC in Shared Memory

• Shared memory is an area of memory that processes use to communicate without operating system intervention
• Synchronization mechanisms are necessary for controlling access to the shared memory to avoid race conditions.
• These mechanisms ensure consistency and prevent data corruption.
• Synchronization is discussed in depth in Chapters 6 and 7.

Bounded-Buffer – Shared-Memory Solution

• A fixed-size buffer is used for communication between producer and consumer processes.
• A counter tracks full buffers

Producer Process (Shared Memory)

• The producer continually produces items.
• It checks if the buffer is full. If it's not, it adds the produced item to the buffer and increments the in-counter,

Consumer Process (Shared Memory)

• The consumer continually consumes items.
• It checks if the buffer is empty. If it's not, it takes the item from the buffer and increments the out-counter.

IPC – Message Passing

• Processes use messages to communicate.
• Functions send(message) and receive(message) are used to exchange messages
• Message size is either fixed or variable.
• Communication links can use different implementations: direct and indirect methods.

Message Passing (Cont.)

• Processes establish a communication link to exchange messages.
• Implementation issues: links, number of links between communicating processes, capacity of a link and its directionality.

Synchronization

• Message passing can be blocking or non-blocking. (synchronous or asynchronous).
• Blocking operations block the sender until the message is received.
• Non-blocking operations let the sender continue without waiting.

Producer-Consumer: Message Passing

• The producer sends messages containing produced items.
• The consumer receives messages, consumes the items and acknowledges.

Buffering

• Message queues are used for buffering, implementing message queue capacities.
• There are three types of ways messages can be buffered: zero capacity,bounded capacity and unbounded capacity queues.

Examples of IPC Systems – Windows

• Windows uses the LPC (Local Procedure Call) facility.
• Communication channels are established using ports.

Sockets

• A socket is an endpoint for communication combining IP address with a port number used by various network services.
• Windows uses sockets for inter-process communication.

Socket Communication

• Sockets allow communication between processes on different machines.

Sockets in Java

• Java has socket classes for various kinds of socket communications

Remote Procedure Calls (RPC)

• RPC abstracts procedure calls between processes over a network
• Uses ports for differentiation between services and stubs (client-side proxy).

Remote Procedure Calls (Cont.)

• The client stub locates the server and marshals parameters
• Server stub unpacks the marshalled parameters and executes the procedure on the server.

Execution of RPC

• A detailed description is shown on how each of the stages in the RPC process proceeds.

This quiz explores the concepts of interprocess communication (IPC) in operating systems, including the characteristics and types of communication between processes. It covers various models and system calls related to process cooperation and message passing mechanisms. Test your knowledge on key IPC operations and typical issues faced in these systems.