Chapter 10

Question 1

IPC

Answer 1

Allow processes to communicate with each other and synchro their actions. This communication is done through the shared mem, which allows to exchange data by writing to or reading from a common mem space.

Question 2

Message based communication

Answer 2

Send(destination, message)
Receive(source, message)

Question 3

Synchro methods of the communication - synchronous message exchange (rendezvous)

Answer 3

Recipient blocks until the message is received and the sender also blocks until it receives an acknowledgement message

Question 4

Synchro methods of the communication - asynchronous message exchange

Answer 4

Sender sends the message to the OS and immediately resumes its operation without waiting for an acknowledgement message, blocking is optional in both sides, buffering is always required because the message needs to be temporary stored until the recipient is ready to process it.

Question 5

Addressing modes of the communication

Answer 5

1. Direct addressing: message is sent directly to a specific process by using process ID.
2. Indirect addressing: message is sent through an intermediary mechanism that stores and forwards the message such as pipes. Messages are stored in mailbox or buffer, from where the recipient can retrieve them.
3. Then we have Unica multicast and broadcast..

Question 6

Properties of messages of the communication

Answer 6

Message format and transmission mode

Question 7

Signals

Answer 7

Are interrupts recreated in software, they are like interrupts to notify processes of events and they are a minimal form of IPC. Processes can send signals using kill( ).

Signal handling always takes place at the transition from kernel to user mode.

If the receiving process is in RUNNING state, signal handling is started immediately
If the receiving process is in READY state, signal is registered in PCB and as soon as the process starts running, the signal handling takes place
If the receiving process is in BLOCKED state, waiting for an event. The I/O call is aborted and the process is set to READY.