Busy Waiting

Busy Waiting

In software engineering, busy-waiting or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input is available, or if a lock is available. Spinning can also be used to generate an arbitrary time delay, a technique that was necessary on systems that lacked a method of waiting a specific length of time. On modern computers with widely differing processor speeds, spinning as a time delay technique often produces unpredictable results unless code is implemented to determine how quickly the processor can execute a "do nothing" loop.

Spinning can be a valid strategy in certain circumstances, most notably in the implementation of spinlocks within operating systems designed to run on SMP systems. In general, however, spinning is considered an anti-pattern and should be avoided, as processor time that could be used to execute a different task is instead wasted on useless activity.