shithub: mc

ref: cae230b08fabfc63c60be35b932fcc9f8c1cb303
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#))
}