Data Races and the Memory Model数据竞争和内存模型

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// from https://golang.org/issue/42598
type module struct {
	v int
}

func foo() {
	mods := []*module{
		&module{v: 0},
		&module{v: 1},
		&module{v: 2},
	}
	type token struct{}
	sem := make(chan token, runtime.GOMAXPROCS(0))
	for _, m := range mods {
		add := func(m *module) {
			sem <- token{}
			go func() {
				*m = module{v: 42} // write
				<-sem
			}()
		}
		add(m) // read
	}
	// Fill semaphore channel to wait for all tasks to finish.
	for n := cap(sem); n > 0; n-- {
		sem <- token{}
	}
}