Appropriate Busy-wait Usage
See also: SpinlockIn low-level programming, busy-waits may actually be desirable. It may not be desirable or practical to implement interrupt-driven processing for every hardware device, particularly those that are seldom accessed. Sometimes it is necessary to write some sort of control data to hardware and then fetch device status resulting from the write operation, status that may not become valid until a number of machine cycles have elapsed following the write. The programmer could call an operating system delay function, but doing so may consume more time than would be expended in spinning for a few clock cycles waiting for the device to return its status.
Read more about this topic: Busy Waiting
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