2021-02-20:手写代码:读写锁。
福哥答案2021-02-20:
四大方法:读加锁,读解锁,写加锁,写解锁。读加锁里有写加锁,读解锁里有写解锁。代码有写线程饥饿现象,但实现简单。
代码用golang编写,代码如下:
package main
import (
"fmt"
"sync"
"time"
)
func main() {
fdd := FddRWMutex{}
go func() {
i := 0
for k := 0; k < 5; k++ {
go func() {
j := i
i++
fdd.RLock()
fmt.Println("读操作", j)
time.Sleep(5 * time.Second)
fdd.RUnlock()
}()
time.Sleep(3 * time.Second)
}
}()
time.Sleep(1000)
fdd.Lock()
fmt.Println("写操作------------------------------------------")
fdd.Unlock()
fmt.Println("有写线程饥饿现象")
}
type FddRWMutex struct {
w sync.Mutex
r sync.Mutex
readerCount int
}
func (rw *FddRWMutex) RLock() {
rw.r.Lock()
rw.readerCount++
if rw.readerCount == 1 {
rw.w.Lock()
}
rw.r.Unlock()
}
func (rw *FddRWMutex) RUnlock() {
rw.r.Lock()
rw.readerCount--
if rw.readerCount == 0 {
rw.w.Unlock()
}
rw.r.Unlock()
}
func (rw *FddRWMutex) Lock() {
rw.w.Lock()
}
func (rw *FddRWMutex) Unlock() {
rw.w.Unlock()
}
执行结果如下:
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