Final answer:
The possible outputs of the program are 2 and 1, depending on the order of thread execution. This is an example of a race condition.
Step-by-step explanation:
The possible outputs of the following two threads running concurrently are:
- Output 1: 2
- In this scenario, thread A is executed first and increments the value of x to 1. However, before thread A can print the value of x, it is preempted by the scheduler. Then, thread B is executed and increments the value of x from 0 to 1. Finally, thread A is resumed and prints the value of x which is 1. Therefore, the printed output is 2.
- Output 2: 1
- In this scenario, thread B is executed first and increments the value of x to 1. However, before thread B can print the value of x, it is preempted by the scheduler. Then, thread A is executed and increments the value of x from 0 to 1. Finally, thread B is resumed and prints the value of x which is 1. Therefore, the printed output is 1.
This is an example of a race condition because the output of the program depends on the relative ordering and timing of the thread executions. The final value of x depends on which thread gets preempted and resumed first by the scheduler.
Complete question is:
In the following program, assume x starts in 0 and is a shared variable for both threads. What are possible outputs of the following two threads running concurrently? Explain how each output is produced (i.e. which order the threads are executed and when they are preempted by the scheduler algorithm to produce the result). Explain why this is an example of a race condition.
A B
x=x+1 x=x+1
print (x)