Question

This week's problems are about another concurrent processing problem: race conditions.

1. Find out what a race condition is, and explain in your own words what goes wrong.

2. Which of the generic architectures considered in lectures is most susceptible to race conditions. Explain your reasoning -- why do you believe that your chosen architecture is most susceptible?

3. Be creative, but realistic: Describe an example (of your own creation) of a system that would be susceptible to a race condition, and what might happen to cause the race condition in your imagined system. Then explain what might be the effect of that race condition in your particular system. The goal in this last part is to imagine a real-world system and to describe it in a way that the marker can understand as well as showing how it could be affected by a race condition.

Answer 1

A race condition is a unprepared situation which occurs when two or more than two systems or threads tackle to perform two or more than two two operations at the same time or we can say that device or threads can fetch shared data and try to modifying or change it but according to the environment of device the operation perform its task correctly when its done in proper sequence.

For Example:

If a process calls a function that's proposed to increase a value (k) which is stored in a database. The function will fetch the current value from database (D) and store it in memory as a variable (E) then increment it (F) and finally write the updated value to database (G). This function's execution is a sequence of steps D-G.

Race condition will happen if process 1 calls this function and proceeds to step F. Meanwhile, it gets preempted by the operating system and another process 2 gets its chance to run. Process 2 calls the same function, completes all the steps D-G and returns. When process 1 resumes, it continues from step F using an old value (k), not process 2  result (k+1).

Race condition would not have happened if process 1 had completed all steps without preemption; or process 2 had been prevented from executing the function until process 1 had completed all steps.