• Also known as Spinning
  • A Process (进程) or Thread repeatedly checks a condition without giving up the CPU until the condition is satisfied

Simple and efficient synchronisation mechanism

Shines when condition is expected to be met very quickly. Like Process (进程) waiting for input from the keyboard.


Can waste Clock Cycle if the condition is not met quickly. For example, a lot of CPU cycles is wasted when a process or thread tries to have a Spinlock on an IO Device, but another process or thread is using the Device Controller to retrieves a large amount of data from IO device.


  • Also known as 自旋锁
  • A type of Busy Waiting specifically used as a lock mechanism where a Thread repeatedly checks and attempts to acquire a lock until it becomes available
  • This is in contrast to Semaphore (信号量) or Mutex (互斥体), which releases the CPU and allows other threads to run while waiting for the condition to be met
  • Usually used to protect short critical sections in a Kernel or Device Driver