Operating Systems Ii - Process Interaction Question

Front 1

Direct process communication

Back 1

Processes must name each other explicitly:
send (P, message) – send a message to process P receive(Q, message) – receive a message from process Q

Links are established automatically

A link is associated with exactly one pair of communicating processes

Exactly one link between each pairs

The link may be unidirectional, but is usually bi-directional

Front 2

Indirect process communication

Back 2

Messages are directed and received from mailboxes (ports)

Each mailbox has a unique id

Processes can communicate only if they share a mailbox
Link established only if processes share a common mailbox

A link may be associated with many processes

Each pair of processes may share several communication links

Link may be unidirectional or bi-directional

Front 3

List the three main process control issues.

Back 3

1. Need for mutual exclusion

2. Deadlock

3. Starvation.

Front 4

Detail mutual exclusion

Back 4

2 or more processes need access to a non-sharable resource.

The resource is a critical resource; portion of the program that uses it is a critical section of the program.

OS may not understand and enforce this restriction because the requirements may not be obvious.

Front 5

Detail deadlock

Back 5

Two processes are waiting for the same resources.

Neither will release the resource that it already owns until it has acquired the other resource and performed the function requiring both resources.

Front 6

Detail starvation

Back 6

OS may grant access to resources to a number of processes while neglecting others.

Front 7

List three degrees of process awareness

Back 7

1. Processes unaware of each other

2. Processes indirectly aware of each other

3. Processes directly aware of each other

Front 8

Processes unaware of each other control problems

Back 8

Mutual exclusion, deadlock & starvation

Front 9

Processes indirectly aware of each other control problems

Back 9

Mutual exclusion, deadlock, starvation & data coherence

Front 10

Processes directly aware of each other control problems

Back 10

Deadlock & starvation