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线程安全问题
假设我要要计算一个用户的积分，为了能够尽快算出用户所有的积分数，我们开启了协程
main.go
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| package main
import (
"fmt"
"sync"
"test/user"
)
func main() {
newuser:= user.User{
Point: 1,
}
wg := sync.WaitGroup{}
wg.Add(2)
go func() {
defer wg.Done()
for i:=0; i<10000; i++ {
newuser.Add()
}
}()
go func() {
defer wg.Done()
for i:=0; i<10000; i++ {
newuser.Minus()
}
}()
wg.Wait()
point := newuser.Get()
fmt.Println(point)
}
|
user/user.go
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| package user
type User struct {
Point int64
}
func (user *User) Add() {
user.Point ++
}
func (user *User) Minus() {
user.Point --
}
func (user *User) Get() int64 {
return user.Point
}
|
结果计算的用户积分每次都不一样，正常情况下应该是 1
加锁处理
user/user.go
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| package user
import "sync"
type User struct {
Point int64
lock sync.Mutex
}
func (user *User) Add() {
user.lock.Lock()
defer user.lock.Unlock()
user.Point ++
}
func (user *User) Minus() {
user.lock.Lock()
defer user.lock.Unlock()
user.Point --
}
func (user *User) Get() int64 {
return user.Point
}
|
使用channel模拟锁
nain.go
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| package main
import (
"fmt"
"sync"
"test/user"
)
func main() {
newuser:= user.User{
Point: 1,
Lock: user.NewMutex(),
}
wg := sync.WaitGroup{}
wg.Add(2)
go func() {
defer wg.Done()
for i:=0; i<10000; i++ {
newuser.Add()
}
}()
go func() {
defer wg.Done()
for i:=0; i<10000; i++ {
newuser.Minus()
}
}()
wg.Wait()
point := newuser.Get()
fmt.Println(point)
}
|
user/user.go
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| package user
type Mutex struct {
ch chan struct{}
}
func NewMutex() *Mutex {
return &Mutex{ch: make(chan struct{}, 1)}
}
func (this *Mutex) Lock() {
this.ch <- struct{}{}
}
func (this *Mutex) UnLock() {
select {
case <-this.ch:
default:
panic("unlock error")
}
}
type User struct {
Point int64
Lock *Mutex
}
func (user *User) Add() {
user.Lock.Lock()
defer user.Lock.UnLock()
user.Point ++
}
func (user *User) Minus() {
user.Lock.Lock()
defer user.Lock.UnLock()
user.Point --
}
func (user *User) Get() int64 {
return user.Point
}
|