Question

in 5-6 sentences

1) What is a race condition? Provide an example.

2) What do we mean by a critical section of code?

3) What do we mean by process or thread synchronization?

Answer 1

Ans 1 : A race condition is a problem that occurs when a system attempts to perform two or more operations at the same time, but because of the nature of the system, the operations must be done in the proper sequence to be done correctly.

Race condition example :

i) b=4

ii) b=b-2

iii) d=b+1

If the above operations executed in the proper sequence then d=3 ,but if the iii operation executed before ii then d = 5 .

Ans 2: Critical section of code is a code segment in which if there are group of coordinating processes then at a given point of time, only one process must be executing its critical section. If any other process also wants to execute its critical section, it must wait until the first one finishes its execution. There are solution to critical section problem :

a) Mutual Exclusion : Only one process can be in its critical section at a given point of time.

b) Progress :If no process is in its critical section and there are thread available then any one thread can enter the critical section and finishes its execution .

c) Bounded Waiting: After a process makes a request for getting into its critical section, there is a limit for how many other processes can get into their critical section, before this process's request is granted. So after the limit is reached, system must grant the process permission to get into its critical section.

Ans 3:Thread synchronization is defined as a mechanism which ensures that two or more concurrent processes or threads do not simultaneously execute some particular program segment known as critical section. Processes' access to critical section is controlled by using synchronization techniques.

For example, suppose that there are three processes, namely A, B, and C. All three of them are concurrently executing, and they need to share a common resource (critical section) . Synchronization should be used here to avoid any conflicts for accessing this shared resource. Hence, when Process A and B both try to access that resource, it should be assigned to only one process at a time. If it is assigned to Process A, the other process (Process B) needs to wait until Process A frees that resource.