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Concurrency in Operating System

In this article, you will learn the concurrency in the operating system with its principles, issues, advantages and disadvantages.

What is Concurrency?

It refers to the execution of multiple instruction sequences at the same time. It occurs in an operating system when multiple process threads are executing concurrently. These threads can interact with one another via shared memory or message passing. Concurrency results in resource sharing, which causes issues like deadlocks and resource scarcity. It aids with techniques such as process coordination, memory allocation, and execution schedule to maximize throughput.

Principles of Concurrency

Today's technology, like multi-core processors and parallel processing, allows multiple processes and threads to be executed simultaneously. Multiple processes and threads can access the same memory space, the same declared variable in code, or even read or write to the same file.

The amount of time it takes a process to execute cannot be simply estimated, and you cannot predict which process will complete first, enabling you to build techniques to deal with the problems that concurrency creates.

Interleaved and overlapping processes are two types of concurrent processes with the same problems. It is impossible to predict the relative speed of execution, and the following factors determine it:

  1. The way operating system handles interrupts
  2. Other processes' activities
  3. The operating system's scheduling policies

Problems in Concurrency

There are various problems in concurrency. Some of them are as follows:

1. Locating the programming errors

It's difficult to spot a programming error because reports are usually repeatable due to the varying states of shared components each time the code is executed.

2. Sharing Global Resources

Sharing global resources is difficult. If two processes utilize a global variable and both alter the variable's value, the order in which the many changes are executed is critical.

3. Locking the channel

It could be inefficient for the OS to lock the resource and prevent other processes from using it.

4. Optimal Allocation of Resources

It is challenging for the OS to handle resource allocation properly.

Issues of Concurrency

Various issues of concurrency are as follows:

1. Non-atomic

Operations that are non-atomic but interruptible by several processes may happen issues. A non-atomic operation depends on other processes, and an atomic operation runs independently of other processes.

2. Deadlock

In concurrent computing, it occurs when one group member waits for another member, including itself, to send a message and release a lock. Software and hardware locks are commonly used to arbitrate shared resources and implement process synchronization in parallel computing, distributed systems, and multiprocessing.

3. Blocking

A blocked process is waiting for some event, like the availability of a resource or completing an I/O operation. Processes may block waiting for resources, and a process may be blocked for a long time waiting for terminal input. If the process is needed to update some data periodically, it will be very undesirable.

4. Race Conditions

A race problem occurs when the output of a software application is determined by the timing or sequencing of other uncontrollable events. Race situations can also happen in multithreaded software, runs in a distributed environment, or is interdependent on shared resources.

5. Starvation

A problem in concurrent computing is where a process is continuously denied the resources it needs to complete its work. It could be caused by errors in scheduling or mutual exclusion algorithm, but resource leaks may also cause it.

Concurrent system design frequently requires developing dependable strategies for coordinating their execution, data interchange, memory allocation, and execution schedule to decrease response time and maximize throughput.

Advantages and Disadvantages of Concurrency in Operating System

Various advantages and disadvantages of Concurrency in Operating systems are as follows:


1. Better Performance

It improves the operating system's performance. When one application only utilizes the processor, and another only uses the disk drive, the time it takes to perform both apps simultaneously is less than the time it takes to run them sequentially.

2. Better Resource Utilization

It enables resources that are not being used by one application to be used by another.

3. Running Multiple Applications

It enables you to execute multiple applications simultaneously.


  1. It is necessary to protect multiple applications from each other.
  2. It is necessary to use extra techniques to coordinate several applications.
  3. Additional performance overheads and complexities in OS are needed for switching between applications.

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