Paused

The PAUSE instruction (x86) or YIELD (ARM) hints to the CPU that the current thread is in a spin-wait loop. Without it, the CPU's speculative execution engine fills the pipeline with spin iterations, which must all be discarded when the lock becomes available.

PAUSE also reduces power consumption and avoids causing memory order violations that slow down both the spinning core and the core holding the lock. The effect is most visible under contention with multiple threads competing for the same lock.

References:

• Intel - PAUSE Instruction
• ARM - YIELD Instruction