英文:
Deadlock in Housie Program. Producer-Consumer Pattern
问题
我正在尝试实现一个 housie 游戏，其中一个 goroutine 生成数字，另外三个 goroutine 检查这些数字是否在它们的令牌中，并在所有数字都被生成后通知生成者。我已经用以下方式在 Golang 中实现了它。这导致了死锁。有什么想法为什么会发生这种情况吗？这是一个“作业问题”，我只是为了更好地学习 Go 而实现它。
package main
import (
"fmt"
"math/rand"
)
type PersonID int
func contains(s []int, e int) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
func Person(called_number chan int, claim_prize chan PersonID, received chan bool, coupon []int, person_id PersonID) {
numFound := 0
for i := 0; i < len(coupon); i++ {
current_number := <-called_number
found := contains(coupon, current_number)
if found {
numFound++
}
if numFound == len(coupon) {
claim_prize <- person_id
} else {
received <- true
}
}
}
func main() {
var called_number chan int
var claim_prize chan PersonID
var received chan bool
tokens := make([][]int, 3)
for i := 0; i < 3; i++ {
tokens[i] = make([]int, 12)
for j := 0; j < 12; j++ {
num := rand.Intn(100) + 1
found := contains(tokens[i], num)
for found {
num = rand.Intn(100) + 1
found = contains(tokens[i], num)
}
tokens[i][j] = num
}
}
go Person(called_number, claim_prize, received, tokens[0], 0)
go Person(called_number, claim_prize, received, tokens[1], 1)
go Person(called_number, claim_prize, received, tokens[2], 2)
claimants := make([]PersonID, 0)
prev_called := make(map[int]bool)
for i := 0; i < 100; i++ {
if len(claimants) == 3 {
break
}
num := rand.Intn(100) + 1
_, ok := prev_called[num]
for ok {
num = rand.Intn(100) + 1
_, ok = prev_called[num]
}
prev_called[num] = true
called_number <- num
for j := 0; j < 3; j++ {
select {
case _ = <-received:
continue
case pid := <-claim_prize:
claimants = append(claimants, pid)
}
}
}
fmt.Println(claimants)
}
编辑：
确切的问题是生产者需要将数字发送给每个消费者。当消费者接收到其令牌中的所有数字时，它可以声明获奖。根据 @OneOfOne 的说法，我对程序进行了一些更改。更改的内容是现在为每个消费者都有一个单独的通道，并在它声明获奖后关闭它。以下是新程序，它仍然发生死锁。
package main
import (
"fmt"
"math/rand"
)
func contains(s []int, e int) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
func Person(called_number chan int, claim_prize chan int, received chan bool, coupon []int, person_id int) {
numFound := 0
for current_number := range called_number {
if contains(coupon, current_number) {
numFound++
}
if numFound == len(coupon) {
fmt.Println(person_id)
claim_prize <- person_id
} else {
received <- true
}
}
}
func main() {
var (
called_number1 = make(chan int, 1)
called_number2 = make(chan int, 1)
called_number3 = make(chan int, 1)
claim_prize = make(chan int, 1)
received = make(chan bool, 1)
)
tokens := make([][]int, 3)
for i := 0; i < 3; i++ {
tokens[i] = make([]int, 12)
for j := 0; j < 12; j++ {
num := rand.Intn(100) + 1
found := contains(tokens[i], num)
for found {
num = rand.Intn(100) + 1
found = contains(tokens[i], num)
}
tokens[i][j] = num
}
}
go Person(called_number1, claim_prize, received, tokens[0], 0)
go Person(called_number2, claim_prize, received, tokens[1], 1)
go Person(called_number3, claim_prize, received, tokens[2], 2)
claimants := make([]int, 0)
prev_called := make(map[int]bool)
for i := 0; i < 100; i++ {
if len(claimants) == 3 {
break
}
num := rand.Intn(100) + 1
_, ok := prev_called[num]
for ok {
num = rand.Intn(100) + 1
_, ok = prev_called[num]
}
prev_called[num] = true
if !contains(claimants, 0) {
called_number1 <- num
}
if !contains(claimants, 1) {
called_number2 <- num
}
if !contains(claimants, 2) {
called_number3 <- num
}
for j := 0; j < 3; j++ {
select {
case _ = <-received:
continue
case pid := <-claim_prize:
if pid == 0 { close(called_number1) }
if pid == 1 { close(called_number2) }
if pid == 2 { close(called_number3) }
claimants = append(claimants, pid)
}
}
}
fmt.Println(claimants)
}
编辑2：这仍然发生死锁，因为即使 goroutine 完成了，我也没有减少等待的通道数量。我进行了修改，现在一切正常运行。
<details>
<summary>英文:</summary>
I am trying to implement a housie game where a goroutine produces numbers, 3 other goroutines check if these are in their tokens and inform the producer if all their numbers were produced. I have implemented it in golang in the following way. This results in a deadlock. Any idea why this is happening? This is a "homework problem", I am just implementing it in go to learn go better.
package main
import (
"fmt"
"math/rand"
)
type PersonID int
func contains(s []int, e int) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
func Person(called_number chan int, claim_prize chan PersonID, received chan bool, coupon []int, person_id PersonID) {
numFound := 0
for i := 0; i < len(coupon); i++ {
current_number := <-called_number
found := contains(coupon, current_number)
if found {
numFound++
}
if numFound == len(coupon) {
claim_prize <- person_id
} else {
received <- true
}
}
}
func main() {
var called_number chan int
var claim_prize chan PersonID
var received chan bool
tokens := make([][]int, 3)
for i := 0; i < 3; i++ {
tokens[i] = make([]int, 12)
for j := 0; j < 12; j++ {
num := rand.Intn(100) + 1
found := contains(tokens[i], num)
for found {
num = rand.Intn(100) + 1
found = contains(tokens[i], num)
}
tokens[i][j] = num
}
}
go Person(called_number, claim_prize, received, tokens[0], 0)
go Person(called_number, claim_prize, received, tokens[1], 1)
go Person(called_number, claim_prize, received, tokens[2], 2)
claimants := make([]PersonID, 0)
prev_called := make(map[int]bool)
for i := 0; i < 100; i++ {
if len(claimants) == 3 {
break
}
num := rand.Intn(100) + 1
_, ok := prev_called[num]
for ok {
num = rand.Intn(100) + 1
_, ok = prev_called[num]
}
prev_called[num] = true
called_number <- num
for j := 0; j < 3; j++ {
select {
case _ = <-received:
continue
case pid := <-claim_prize:
claimants = append(claimants, pid)
}
}
}
fmt.Println(claimants)
}
EDIT:
The exact problem is that that the producer needs to send the number to each of the consumers. When a consumer receives all the numbers in it's token, it can claim the prize. Based on what @OneOfOne said, I have made some changes to the program. The changes are that now there is a separate channels for each of the consumers and I am closing it after it claims a prize. Below is the new program, it still deadlocks.
package main
import (
"fmt"
"math/rand"
)
func contains(s []int, e int) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
func Person(called_number chan int, claim_prize chan int, received chan bool, coupon []int, person_id int) {
numFound := 0
for current_number := range called_number {
if contains(coupon, current_number) {
numFound++
}
if numFound == len(coupon) {
fmt.Println(person_id)
claim_prize <- person_id
} else {
received <- true
}
}
}
func main() {
var (
called_number1 = make(chan int, 1)
called_number2 = make(chan int, 1)
called_number3 = make(chan int, 1)
claim_prize = make(chan int, 1)
received = make(chan bool, 1)
)
tokens := make([][]int, 3)
for i := 0; i < 3; i++ {
tokens[i] = make([]int, 12)
for j := 0; j < 12; j++ {
num := rand.Intn(100) + 1
found := contains(tokens[i], num)
for found {
num = rand.Intn(100) + 1
found = contains(tokens[i], num)
}
tokens[i][j] = num
}
}
go Person(called_number1, claim_prize, received, tokens[0], 0)
go Person(called_number2, claim_prize, received, tokens[1], 1)
go Person(called_number3, claim_prize, received, tokens[2], 2)
claimants := make([]int, 0)
prev_called := make(map[int]bool)
for i := 0; i < 100; i++ {
if len(claimants) == 3 {
break
}
num := rand.Intn(100) + 1
_, ok := prev_called[num]
for ok {
num = rand.Intn(100) + 1
_, ok = prev_called[num]
}
prev_called[num] = true
if !contains(claimants, 0) {
called_number1 <- num
}
if !contains(claimants, 1) {
called_number2 <- num
}
if !contains(claimants, 2) {
called_number3 <- num
}
for j := 0; j < 3; j++ {
select {
case _ = <-received:
continue
case pid := <-claim_prize:
if pid == 0 { close(called_number1) }
if pid == 1 { close(called_number2) }
if pid == 2 { close(called_number3) }
claimants = append(claimants, pid)
}
}
}
fmt.Println(claimants)
}
EDIT2: This still deadlocked because I was not reducing the number of channels to wait for even after the goroutines were completed. Did that and everything works.
</details>
# 答案1
**得分**: 2
几个问题：
1. 你正在使用一个空通道，所以它会永远阻塞，但出于某种原因它没有引发错误。
2. 另外，你的第二个内部循环会无限期地阻塞，因为它在等待读取，但没有发送任何内容。
3. 在 `Person` 的循环结束后，`called_number <- num` 会永远阻塞。
//编辑
部分可工作的代码：http://play.golang.org/p/3At5nuJTuk
但是逻辑有问题，你需要重新考虑一下。
<details>
<summary>英文:</summary>
Few problems:
1. You're using a nil channel, so it just blocks forever, for some reason it's not panicing.
2. Also, your second inner loop will block indefinitely because it's waiting to read but nothing is being sent.
3. After your `Person`'s loop ends, `called_number <- num` will block forever.
//edit
Kinda-working-code : http://play.golang.org/p/3At5nuJTuk
But the logic is flawed, you will have to rethink it.
</details>
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