futex_requeue - Wake some number of threads waiting on a futex, and move more waiters to another wait queue.
#include <zircon/syscalls.h>
zx_status_t zx_futex_requeue(const zx_futex_t* value_ptr, uint32_t wake_count,
int current_value, const zx_futex_t* requeue_ptr,
uint32_t requeue_count);
Requeuing is a generalization of waking. First, the kernel verifies that the value in current_value matches the value of the futex at value_ptr, and if not reports ZX_ERR_BAD_STATE. After waking wake_count threads, requeue_count threads are moved from the original futex's wait queue to the wait queue corresponding to requeue_ptr, another futex.
This requeueing behavior may be used to avoid thundering herds on wake.
futex_requeue() returns ZX_OK on success.
ZX_ERR_INVALID_ARGS value_ptr isn't a valid userspace pointer, or value_ptr is the same futex as requeue_ptr, or value_ptr or requeue_ptr is not aligned, or requeue_ptr is NULL but requeue_count is positive.
ZX_ERR_BAD_STATE current_value does not match the value at value_ptr.