ref: 330b2e6a59402d3a290629f409d77c2692973f3c
dir: /lib/thread/test/mutex.myr/
use std
use thread
use thrtestutil
const Nherd = 20
var val : uint64 = 0
var mtx : thread.mutex
var done
const main = {
	mtx = thread.mkmtx()
	done = thread.mkwg(Nherd)
	thrtestutil.mkherd(Nherd, incvar)
	thread.wgwait(&done)
	if val != 1000 * (Nherd : uint64)
		std.fatal("mutexes are broken, got {}\n", val)
	;;
}
const incvar = {
	for var i = 0; i < 1000; i++
		thread.mtxlock(&mtx)
		val++
		thread.mtxunlock(&mtx)
	;;
	thread.wgpost(&done)
}