Futex

futex_waitv Blocks on Multiple Futex Words in One Wait

A traditional futex wait names one futex word. That maps cleanly to a mutex or condition whose blocking state is represented by one shared 32-bit value. Some synchronization designs instead need a thread to sleep until any member of several independent states changes. futex_waitv() provides that vector wait. The caller supplies an array of wait descriptors, each containing a futex address and an expected value. The kernel checks the vector and blocks only while every entry still matches its expected state.