Ch.7

Question 1

Conditions for deadlocks to occur ( deadlock characterization)

Answer 1

• mutual exclusion
• hold and wait
• no preemption
  Circular wait

Question 2

Methods for handling deadlocks we

Answer 2

• ensure that the system will never enter a deadlock
• allow the system to enter a deadlock state and then recover
• ignore the problem and pretend that deadlocks never occur in the system

Question 3

Deadlock detection

Answer 3

• allow system to enter deadlock state
• detection algorithm
• recovery scheme

Question 4

Instances of a resource type

Answer 4

Available

Allocation

Request

Question 5

Recovery a deadlock ways

Answer 5

• abort all deadlock process
• abort one process at a time until the deadlock circle is eliminated

Question 6

How to choose which process to abort

Answer 6

• process priority
• progress
• resources used
• res courses needed
• impact on system
• nature of the process

Question 7

Recovery from dead lock: resource preemption

Answer 7

• selecting a victim
• rollback

Starvation

Question 8

Every process uses a resource in three steps

Answer 8

Request

Use

Release

Question 9

Resource allocation graph

No cycles—> ???
Cycle exists—> ???

Answer 9

No deadlock

If only one instance per resource type—> dead lock

If several instances per resource type—> possibility of dead lock

Question 10

If a system is in a safe state—>??

If a system is in an unsafe state—>??

Avoidance—>??

Answer 10

No deadlocks

Possibility of deadlocks

Ensure that a system will never renter an unsafe state

Question 11

Single instance of a resource type use:—>??

Multiple instances per of a resource type use:—>??

Answer 11

Use a resource allocation graph

Use the bankers algorithm