futex_wait - Wait on a futex.
#include <zircon/syscalls.h>
zx_status_t zx_futex_wait(zx_futex_t* value_ptr, int current_value,
zx_time_t deadline);
Waiting on a futex (or acquiring it) causes a thread to sleep until
the futex is made available by a call to zx_futex_wake
. Optionally,
the thread can also be woken up after the deadline (with respect
to ZX_CLOCK_MONOTONIC) passes.
futex_wait() returns ZX_OK on success.
ZX_ERR_INVALID_ARGS value_ptr is not a valid userspace pointer, or value_ptr is not aligned.
ZX_ERR_BAD_STATE current_value does not match the value at value_ptr.
ZX_ERR_TIMED_OUT The thread was not woken before deadline passed.