shithub: mc

ref: 74d91a0021de012908cfdb35fb61a1473a376130
dir: /lib/thread/mutex.myr/

use std

use "atomic"

pkg thread =
	type mutex = struct
		_state	: uint32
	;;	

	const mkmtx	: (-> mutex)
	const mtxlock	: (mtx : mutex# -> void)
	const mtxtrylock	: (mtx : mutex# -> bool)
	const mtxunlock	: (mtx : mutex# -> void)
;;

const mkmtx = {
	-> [._state = 0]
}

/* a shitty spinlock */
const mtxlock = {mtx
	/* first fast */
	for var i = 0; i < 1000; i++
		if xcas(&mtx._state, 0, 1) == 0
			-> void
		;;
		std.nanosleep(0)
	;;
	
	/* then slower */
	for var i = 0; i < 1000; i++
		if xcas(&mtx._state, 0, 1) == 0
			-> void
		;;
		std.nanosleep(10_000) /* 10 us */
	;;

	/* even slower */
	for var i = 0; i < 1000; i++
		if xcas(&mtx._state, 0, 1) == 0
			-> void
		;;
		std.nanosleep(100_000) /* 100 us */
	;;

	/* I'm rip van winkle! */
	while true
		if xcas(&mtx._state, 0, 1) == 0
			-> void
		;;
		std.nanosleep(1000_000) /* 1 ms */
	;;
}

const mtxtrylock = {mtx
	-> xcas(&mtx._state, 0, 1) == 0
}

	
const mtxunlock = {mtx
	xset(&mtx._state, 0)
}