What is process synchronization in operating systems? (2024)

Process synchronization can be classified into two main types: mutual exclusion and cooperation. Mutual exclusion means that only one process can access a critical section of code or a shared resource at a time, while other processes have to wait. This prevents race conditions, where the outcome of the execution depends on the order or timing of the processes. Cooperation means that multiple processes can work together to achieve a common goal, such as producing or consuming data, by communicating and synchronizing their actions. This requires coordination, where the processes agree on the order and timing of their operations.

Operating systems provide various mechanisms to implement process synchronization, such as locks, semaphores, monitors, message passing, and condition variables. These mechanisms allow processes to acquire and release access to shared resources, signal and wait for events, exchange information, and enforce ordering constraints. Depending on the mechanism, the synchronization can be done in user space or kernel space, and can be either busy-waiting or blocking. Busy-waiting means that a process repeatedly checks a condition until it becomes true, while blocking means that a process suspends its execution until it is notified by another process or the system.

Process synchronization is not a trivial task, as it involves solving several problems and challenges, such as deadlock, starvation, priority inversion, and concurrency bugs. Deadlock occurs when a set of processes are waiting for each other to release resources that they hold, and none of them can proceed. Starvation occurs when a process is indefinitely delayed from accessing a resource due to the scheduling or allocation policies. Priority inversion occurs when a high-priority process is blocked by a low-priority process that holds a resource that the high-priority process needs. Concurrency bugs occur when the synchronization mechanisms are incorrectly used or implemented, leading to unexpected or incorrect results.

Process synchronization can be illustrated by using some classic examples, such as the producer-consumer problem, the readers-writers problem, the dining philosophers problem, and the bounded buffer problem. The producer-consumer problem involves two processes that share a buffer, where one process produces data and the other process consumes data. The synchronization challenge is to ensure that the producer does not overflow the buffer and the consumer does not underflow the buffer. The readers-writers problem involves multiple processes that access a shared file, where some processes only read the file and some processes write to the file. The synchronization challenge is to allow multiple readers to access the file simultaneously, but only one writer at a time. The dining philosophers problem involves five processes that share five resources, where each process alternates between thinking and eating. The synchronization challenge is to prevent deadlock and starvation among the processes. The bounded buffer problem involves n processes that share a buffer of size m, where each process either inserts or removes an item from the buffer. The synchronization challenge is to ensure that the buffer is not empty when a process tries to remove an item, and not full when a process tries to insert an item.

Process synchronization is a key concept in operating systems that enables multiple processes to execute concurrently and correctly. By understanding the types, mechanisms, problems, and examples of process synchronization, you can appreciate how operating systems manage and coordinate the activities of processes that share resources and communicate with each other.

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

Computer Science

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