77 lines
2.1 KiB
Markdown
77 lines
2.1 KiB
Markdown
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### sync 包低级同步原语使用场景
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- 高性能的临界区（critical section）同步机制场景
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- 不想转移结构体对象所有权，但又要保证结构体内部状态数据的同步访问的场景
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### sync包原语使用注意事项
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- 不要将原语复制后使用
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- 用闭包或者传递原语变量的地址（指针）
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### mutex 互斥锁
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- 零值可用，不用初始化
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- Lock，Unlock
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- lock状态下任何goroutine加锁都会阻塞
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### RWMutex 读写锁
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- 零值可用，不用初始化
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- RLock，RUnlock 加读锁，解读锁
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- Lock，Unlock 加写锁，解写锁
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- 加读锁状态下，不会阻塞加读锁，会阻塞加写锁
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- 加写锁状态下，会阻塞加读锁与写锁的goroutine
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### sync.Cond 条件变量
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- sync.Cond是传统的条件变量原语概念在 Go 语言中的实现
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- 可以把一个条件变量理解为一个容器，这个容器中存放着一个或一组等待着某个条件成立的 Goroutine
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- 当条件成立后，处于等待状态的 Goroutine 将得到通知，并被唤醒继续进行后续的工作
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```go
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type signal struct{}
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var ready bool
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func worker(i int) {
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fmt.Printf("worker %d: is working...\n", i)
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time.Sleep(1 * time.Second)
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fmt.Printf("worker %d: works done\n", i)
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}
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func spawnGroup(f func(i int), num int, groupSignal *sync.Cond) <-chan signal {
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c := make(chan signal)
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var wg sync.WaitGroup
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for i := 0; i < num; i++ {
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wg.Add(1)
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go func(i int) {
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groupSignal.L.Lock()
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for !ready {
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groupSignal.Wait()
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}
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groupSignal.L.Unlock()
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fmt.Printf("worker %d: start to work...\n", i)
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f(i)
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wg.Done()
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}(i + 1)
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}
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go func() {
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wg.Wait()
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c <- signal(struct{}{})
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}()
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return c
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}
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func main() {
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fmt.Println("start a group of workers...")
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groupSignal := sync.NewCond(&sync.Mutex{})
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c := spawnGroup(worker, 5, groupSignal)
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time.Sleep(5 * time.Second) // 模拟ready前的准备工作
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fmt.Println("the group of workers start to work...")
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groupSignal.L.Lock()
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ready = true
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groupSignal.Broadcast()
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groupSignal.L.Unlock()
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<-c
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fmt.Println("the group of workers work done!")
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}
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```
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