ref: 91e0b9594c2852d446d238a1678231be4d1c13b5
dir: /lib/thread/condvar+openbsd:6.2.myr/
use std use sys use "atomic" use "common" use "futex" use "mutex" pkg thread = type cond = struct _mtx : mutex# _seq : ftxtag ;; const mkcond : (mtx : mutex# -> cond) const condwait : (cond : cond# -> void) const condsignal : (cond : cond# -> void) const condbroadcast : (cond : cond# -> void) ;; const mkcond = {mtx -> [._mtx = mtx, ._seq = 0] } const condwait = {cond var mtx = cond._mtx var seq = xget(&cond._seq) mtxunlock(mtx) ftxwait(&cond._seq, seq, -1) /* In the event of a broadcast, we need to atomically set the mutex to contended. This allows us to pass responsibility for waking up the potential other waiters from the requeue operation on to the unlocker of the mutex. */ mtxcontended(mtx) } const condsignal = {cond : cond# xadd(&cond._seq, 1) ftxwake(&cond._seq) } const condbroadcast = {cond : cond# xadd(&cond._seq, 1) sys.futex((&cond._seq : uint32#), sys.Futexrequeue, 1, (0x7fffffff : sys.timespec#), (&cond._mtx._state : uint32#)) }