Synchronization Concepts: Review Questions - angrave/SystemProgramming GitHub Wiki

Note thread-programming synchronization problems are on a separate wiki page. This page focuses on conceptual topics. Question numbers subject to change

Q1

What do each of the Coffman conditions mean? (e.g. can you provide a definition of each one)

• Hold and wait
• Circular wait
• No pre-emption
• Mutual exclusion

Q2

Give a real life example of breaking each Coffman condition in turn. A situation to consider: Painters, paint and paint brushes. Hold and wait Circular wait No pre-emption Mutual exclusion

Q3

Identify when Dining Philosophers code causes a deadlock (or not). For example, if you saw the following code snippet which Coffman condition is not satisfied?

// Get both locks or none.
pthread_mutex_lock(a);
if (pthread_mutex_trylock(b)) { /* failed */
    pthread_mutex_unlock(a);
    ...
}

Q4

How many processes are blocked?

• P1 acquires R1
• P2 acquires R2
• P1 acquires R3
• P2 waits for R3
• P3 acquires R5
• P1 acquires R4
• P3 waits for R1
• P4 waits for R5
• P5 waits for R1

Q5

How many of the following statements are true for the reader-writer problem?

• There can be multiple active readers
• There can be multiple active writers
• When there is an active writer the number of active readers must be zero
• If there is an active reader the number of active writers must be zero
• A writer must wait until the current active readers have finished