我是码客
2022-11-05
unbuffered := make(chan int)
a := <- unbuffered // 阻塞
unbuffered := make(chan int)
// 1) 阻塞
a := <- unbuffered
// 2) 阻塞
unbuffered <-
// 3) 同步
go func() { <-unbuffered }()
unbuffered <- buffered := make(chan int, ) // 4) 阻塞 a := <- buffered // 5) 不阻塞 buffered <- // 6) buffer满，阻塞 buffered <-
c := make(chan int) close(c) fmt.Println(<-c) //接收并输出chan类型的零值，这里int是0
func TryReceive(c <-chan int) (data int, more, ok bool) {
select {
case data, more = <- c:
return data, more, true
}
default:
return , true, false
}func TryReceiveWithTimeout(c <-chan int, duration time.Duration) (data int, more, ok bool) {
select {
case data, more = <-c:
return data, more, true
case <- time.After(duration):
return , true, false
}
}package main import (
"fmt"
"runtime"
"time"
) var i int64 = func main() {
runtime.GOMAXPROCS()
go func() {
for {
fmt.Println("i is", i)
time.Sleep(time.Second)
}
}() for {
i +=
}
}
==================
WARNING: DATA RACE
Read at 0x00000121e848 by goroutine :
main.main.func1()
/Users/saas/src/awesomeProject/datarace/main.go: +0x3e
Previous write at 0x00000121e848 by main goroutine:
main.main()
/Users/saas/src/awesomeProject/datarace/main.go: +0x7b
Goroutine (running) created at:
main.main()
/Users/saas/src/awesomeProject/datarace/main.go: +0x4f
==================package main import (
"fmt"
"runtime"
"sync"
"time"
) var i int64 = func main() {
runtime.GOMAXPROCS()
var m sync.Mutex
go func() {
for {
m.Lock()
fmt.Println("i is", i)
m.Unlock()
time.Sleep(time.Second)
}
}() for {
m.Lock()
i +=
m.Unlock()
}
}
package main import (
"fmt"
"runtime"
"time"
) var i int64 = func main() {
runtime.GOMAXPROCS()
c := make(chan int64)
go func() {
for {
fmt.Println("i is", <-c)
time.Sleep(time.Second)
}
}() for {
i +=
c<-i
}
}
type Spinlock struct {
state *int32
}
const free = int32()
func (l *Spinlock) Lock() {
for !atomic.CompareAndSwapInt32(l.state, free, ) { //如果state等于0就赋值为42
runtime.Gosched() //让出CPU
}
}
func (l *Spinlock) Unlock(){
atomic.StoreInt32(l.state, free) // 所有操作state变量的操作都应该是原子的
}func restore(repos []string) error {
errChan := make(chan error, )
sem := make(chan int, ) // four jobs at once
var wg sync.WaitGroup
wg.Add(len(repos))
for _, repo := range repos {
sem <-
go func() {
defer func() {
wg.Done()
<- sem
}()
if err := fetch(repo); err != nil {
errChan <- err
}
}()
}
wg.Wait()
close(sem)
close(errChan)
return <- errChan
}func restore(repos []string) error {
errChan := make(chan error, )
sem := make(chan int, ) // four jobs at once
var wg sync.WaitGroup
wg.Add(len(repos))
for _, repo := range repos {
go worker(repo, sem, &wg, errChan)
}
wg.Wait()
close(errChan)
return <- errChan
}
Func worker(repo string, sem chan int, wg *sync.WaitGroup, errChan chan err) {
defer wg.Done()
sem <-
if err := fetch(repo); err != nil {
select {
case errChan <- err:
// we are the first worker to fail
default:
// some other failure has already happened, drop this one
}
}
<- sem
}