Mutex
Mutex
Mutex 代表 Mutual Exclusion(互斥)。互斥提供了一种并发安全的方式来表示对共享资源访问的独占。下面是一个简单的两个 goroutine，它们试图增加和减少一个公共值，并使用 Mutex 来同步访问：
var count int
var lock sync.Mutex
increment := func() {
lock.Lock() // 1
defer lock.Unlock() // 2
count++
fmt.Printf("Incrementing: %d\n", count)
}
decrement := func() {
lock.Lock() // 1
defer lock.Unlock() // 2
count--
fmt.Printf("Decrementing: %d\n", count)
}
// Increment
var arithmetic sync.WaitGroup
for i := 0; i <= 5; i++ {
arithmetic.Add(1)
go func() {
defer arithmetic.Done()
increment()
}()
}
// Decrement
for i := 0; i <= 5; i++ {
arithmetic.Add(1)
go func() {
defer arithmetic.Done()
decrement()
}()
}
arithmetic.Wait()
fmt.Println("Arithmetic complete.")
很多时候我们希望对某个对象屏蔽并发访问，可以将 Mutex 添加伪结构体的某个属性：
package main
import (
"fmt"
"sync"
"time"
)
type User struct {
Name string
Locker *sync.Mutex
}
func (u *User) SetName(wati *sync.WaitGroup, name string) {
defer func() {
fmt.Println("Unlock set name:", name)
u.Locker.Unlock()
wati.Done()
}()
u.Locker.Lock()
fmt.Println("Lock set name:", name)
time.Sleep(1 * time.Second)
u.Name = name
}
func (u *User) GetName(wati *sync.WaitGroup) {
defer func() {
fmt.Println("Unlock get name:", u.Name)
u.Locker.Unlock()
wati.Done()
}()
u.Locker.Lock()
fmt.Println("Lock get name:", u.Name)
time.Sleep(1 * time.Second)
}
func main() {
user := User{}
user.Locker = new(sync.Mutex)
wait := &sync.WaitGroup{}
names := []string{"a", "b", "c"}
for _, name := range names {
wait.Add(2)
go user.SetName(wait, name)
go user.GetName(wait)
}
wait.Wait()
}