关于 golang 互斥锁的一个疑问

下面是 go playground 的输出。
func passes lock by value: sync.Mutex
这一句，锁不能用值传递，改成全局变量或者放在结构体里面再试。

./prog.go:38:8: call of func(i int, m sync.Mutex) {
fmt.Println("Not lock: ", i)
mutex.Lock()
fmt.Println("Lock: ", i)
time.Sleep(time.Second)
fmt.Println("Unlock: ", i)
mutex.Unlock()
defer wait.Done()
} copies lock value: sync.Mutex
./prog.go:30:20: func passes lock by value: sync.Mutex
./prog.go:58:8: call of func(c *counter, m sync.Mutex) {
m.Lock()
defer m.Unlock()
c.value++
wg.Done()
} copies lock value: sync.Mutex
./prog.go:53:25: func passes lock by value: sync.Mutex
Go vet exited.

数数：1000

play.go

gramyang

2019-07-08 13:51:25 +08:00

@Maboroshii 不行

gramyang

2019-07-08 14:00:00 +08:00

@Maboroshii 把锁换成指针传递后可以了。。。。。

Maboroshii

2019-07-08 14:01:23 +08:00

@gramyang #2

type counter struct {
sync.Mutex
value int
}

func test2() {
runtime.GOMAXPROCS(1)
var wg sync.WaitGroup
wg.Add(1000)
c := new(counter)
c.value=0
for i := 0; i < 1000; i++ {
go func(c *counter) {
c.Lock()
defer c.Unlock()
c.value++
wg.Done()
}(c)
}
wg.Wait()
fmt.Println("数数：", c.value)
}

func main() {
test2()
}

xeaglex

2019-07-08 17:18:14 +08:00

[官方文档]( https://godoc.org/sync) 第一段话说了：

> Values containing the types defined in this package should not be copied.

pubby

2019-07-08 18:06:24 +08:00

想起了以前偷懒这样写

client := &http.Client{}
t := *( http.DefaultTransport.(*http.Transport))
t.TLSClientConfig = &tls.Config{InsecureSkipVerify: true}
client.Transport = http.RoundTripper(&t)

结果高并发时 http 内部锁随机炸