Synchronization Concepts: Review Questions - lyuanschool/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 for 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