Description: Blocking is a condition where a process cannot continue its execution because it is waiting for a resource that is being used by another process. This phenomenon is common in operating systems and databases, where multiple processes may attempt to access the same resources simultaneously. Blocking can lead to a decrease in system performance, as the processes involved remain in a waiting state, resulting in inefficient use of system resources. There are different types of blocking, such as mutual blocking, where two or more processes block each other, and wait blocking, where a process waits indefinitely for a resource that is never released. Proper management of blocking is crucial to ensure the efficiency and stability of computer systems, and various strategies are implemented to prevent and resolve blocking situations, such as the use of deadlock detection algorithms and recovery techniques.
History: The concept of blocking in computer systems dates back to the early developments of operating systems in the 1960s. As systems became more complex and multitasking processes became common, issues related to concurrent access to shared resources emerged. In 1971, Edsger Dijkstra introduced the concept of ‘blocking’ in his work on process synchronization, laying the groundwork for the development of deadlock prevention and detection algorithms. Since then, research in this area has evolved, leading to various techniques and models for managing blocking in operating systems and databases.
Uses: Blocking is used in computing systems to manage access to shared resources such as memory, files, and input/output devices. In databases, blocking is essential to ensure data integrity during concurrent transactions. Additionally, it is applied in concurrent programming to prevent race conditions and ensure that processes execute in an orderly manner. Blocking management techniques are crucial in high-concurrency environments, such as web servers and distributed applications, where multiple users may attempt to access the same resources simultaneously.
Examples: An example of blocking can be observed in a database management system where two transactions attempt to update the same row in a table. If the first transaction locks the row for its update, the second transaction will remain waiting until the first completes its operation. Another example is found in computing systems, where a process attempting to access a network resource that is already in use by another process may become blocked until the resource is released.
