Operating System – CodeWindow.in

In an operating system, a system call is a request made by a user-level process to the kernel to perform a specific operation on behalf of the process. System calls can be categorized into two types: blocking and non-blocking system calls.

Blocking system calls are those that cause the calling process to be blocked until the requested operation is completed. In other words, when a process makes a blocking system call, the kernel may put the process into a blocked state until the requested operation is finished. The process will remain blocked and will not execute any code until the system call returns with the desired result. Examples of blocking system calls include read(), write(), and accept().

On the other hand, non-blocking system calls return immediately, regardless of whether the requested operation has completed or not. If the operation has not completed, the system call will return an error indicating that the operation is still in progress. The calling process can continue executing other code while waiting for the operation to complete. The process can check the status of the operation using other system calls such as select() or poll(). Examples of non-blocking system calls include fcntl() with the O_NONBLOCK flag and socket() with the SOCK_NONBLOCK flag.

The choice between blocking and non-blocking system calls depends on the requirements of the application. Blocking system calls simplify programming by allowing applications to wait for the requested operation to complete before continuing execution. However, they may cause delays and reduce overall system performance, especially in multi-threaded or multi-process environments. Non-blocking system calls can increase system performance by allowing applications to perform other tasks while waiting for I/O operations to complete. However, they require more complex programming logic to handle asynchronous I/O events.