Difference between Spinlock and Mutex in Operating System

When many processes access and modify the same data simultaneously, the outcome is specified by the sequence in which the processes are completed. It's known as a racing condition. Multiple processes or threads running simultaneously may cause a race condition, and as a result, it may lead to data inconsistency. Spinlock and mutex are two strategies for synchronizing processes or threads in the operating system.

In this article, you will learn about the difference between Spinlock and Mutex in the operating system. But before discussing the differences, you must know about Spinlock and Mutex in the operating system.

What is a Spinlock?

A locking mechanism is called a spinlock. It permits a thread to wait until the lock becomes accessible. In other words, a thread spins or waits in a loop until the lock becomes accessible. After obtaining the lock, the thread may hold the spinlock until releasing it. In some systems, if the thread holding the lock is blocked or enters a state of sleep, the spinlock could be automatically launched.

A spinlock also prevents overhead from context switching or operating system process rescheduling. Moreover, it is an effective mechanism for temporarily blocking threads. As a result, most OS kernels employ spinlocks. However, if a thread holds a spinlock for an extended time, other threads may be unable to execute. Other threads may attempt to acquire the lock repeatedly in this state, while the thread holding the lock doesn't start to release it. Usually, it may happen in single processor systems.

What is Mutex?

The mutex is another locking method in OS. A process obtains the mutex condition before using the shared resource. After that, the lock is released by the process. Similarly, only one process may access the shared resource at a time. As a result of this locking mechanism, only one process may run in the vital part at a time.

When the process requires using a shared resource or access to a shared variable, it uses the acquire() procedure to occupy the lock. After the critical section's execution is complete, the lock is released using the release() method. The other processes are unable to utilize the shared variable in the critical area, while one process has the lock. They have to wait till the mutex is unlocked in line.

Key differences between Spinlock and Mutex in the operating system

Here, you will learn about the various key differences between Spinlock and Mutex in OS. Some main differences between Spinlock and Mutex in OS are as follows:

1. Spinlock is a type of lock that causes a thread attempting to obtain it to check for its availability while waiting in a loop continuously. On the other hand, a mutex is a program object designed to allow different processes may take turns sharing the same resource.
2. The spinlock temporarily prevents a thread from moving. In contrast, the mutex may block a thread for an extended amount of time.
3. Spinlock is useful for limited critical sections; else, it wastes the CPU cycles. On the other hand, the mutex is useful for crucial extended areas where frequent context switching would add overhead.
4. Spinlock makes no use of context switching. In contrast, mutex involves context switching.
5. The process in spinlock may not sleep while waiting for the lock. In contrast, the process in mutex may sleep while waiting for the lock.
6. Spinlock disables preemption. On the other hand, mutex supports preemption.

Head-to-head comparison between the Spinlock and Mutex in Operating System

The OS has various head-to-head comparisons between Spinlock and Mutex in the operating system. Some comparisons of the Spinlock and Mutex in the operating system are as follows:

Conclusion

In summary, mutex and spinlock are two methods for synchronizing processes or threads. The key distinction between mutex and spinlock is that the spinlock requires a thread attempting to acquire the lock to wait in a loop and periodically check for its availability. In contrast, mutex allows multiple processes to share a resource alternately. Both spinlock and mutex are locking techniques, but the workings of these techniques are different.