Concurrency: ThreadInteraction & Deadlocks

Question 1

What are 2 types of synchronization?

Answer 1

• Mutual Exclusion (Wechselseitiger Ausschluss), allows max 1 thread to access the shared resource at once
• Condition Synchronization (Zustandssynchronisation): thread waits for a specific condition, another thread executes methods to produce this condition

Question 2

What’s the purpose of the “synchronized” statement?

Answer 2

To mark critical sections within the code in order to guarantee mutual exclusion

Question 3

What are the 2 possible forms of the synchronized statement?

Answer 3

• Synchronized Method

- Synchronized Block

Question 4

What’s the purpose of a monitor?

Answer 4

A monitor acts as a Lock for exclusive access right. Max. 1 thread can own the monitor.

1. Acquire monitor at start of synchronized block
2. Within synchronized block
3. Release monitor

Question 5

If we choose to call a synchronized block from another synchronized block, which case is less risky:

a) use the same monitor object
b) use different monitor object

Answer 5

a) use the same monitor object won’t block a thread. If it’s 2 different monitors there’s the risk of a deadlock

Question 6

What’s the purpose of condition synchronization?

Answer 6

To control the cooperation of threads.