Busy Waiting

CORE DEFINITION

In software engineering, busy waiting (also known as spinning; English: Busy waiting, busy-looping, spinning) is a technique based on a process repeatedly checking whether a condition is true, which may be keyboard input or whether a lock is available. Busy waiting can also be used to generate an arbitrary time delay, if the system does not provide a method to generate a specific length of time, then busy waiting is needed. Different computer processors vary greatly in speed, especially some processors are designed to dynamically adjust their rate based on external factors (such as load on the operating system). Therefore, busy waiting as a time delay technique is prone to unpredictable and even inconsistent results, unless the implementation code determines the speed at which the processor executes the 'do nothing' loop, or the loop code explicitly checks the real-time clock. In some cases, busy waiting is an effective strategy, especially on operating systems that implement spinlock designs for symmetric multiprocessing. However, in general, busy waiting is an anti-pattern that should be avoided; processor time should be used to perform other tasks rather than being wasted on useless activity.