Scheduling

Question 1

What does Thread Scheduling deal with?

Answer 1

Thread scheduling deals with allocating threads to CPUs and deciding how long each thread will execute.

Question 2

Give a brief descrirtion of a thread when it is in a New State

Answer 2

A thread object has been created, but the thread as such does not yet exist because ‘start’ has not been called yet.

Question 3

Give a brief descrirtion of a thread when it is in a Runnable State

Answer 3

After ‘start’ has been called on a thread it moves into the ‘runnable’ state – this is the default state for a thread. Many threads might be in the ‘runnable’ state but only one (per cpu) will actually be executing. (The scheduler determines which threads will actually ‘run’).

Question 4

Give a brief descrirtion of a thread when it is in a Blocked State

Answer 4

If a thread executes a sleep(), wait(), or join() method, or when it is blocked when trying to read data, or when it is waiting for a lock on a synchronized object, it moves into the ‘blocked’ state. When it unblocks, it moves into the runnable state.

Question 5

Give a brief descrirtion of a thread when it is in a Terminated State

Answer 5

When a thread’s run() method finished it moves to the terminated state (i.e. the ‘thread’ terminates).

Question 6

Name atleast one situation where the schedular will run a different thread

Answer 6

One of the currently executing threads exits the Runnable state, i.e. it enters the blocked state (via a ‘wait’ or ‘sleep’ or ‘yield’ etc.) or it terminates.

A higher priority thread than one of the currently running threads enters the Runnable state. The lower priority thread is preempted and the higher priority thread is run.