我正在排隊(duì) 大約30%的運(yùn)行都會(huì)發(fā)生這種情況，其余的都完成了，沒(méi)有錯(cuò)誤。我想我使用WaitGroup的方式是錯(cuò)誤的，但不確定我做錯(cuò)了什么。也許有人可以幫助我識(shí)別我的錯(cuò)誤？謝謝！fatal error: all goroutines are asleep - deadlock!wg.Wait()package mainimport ( "fmt" "math/rand" "sync" "time")const ( numOfPhilosophers = 5 numOfMeals = 3 maxEaters = 2)var doOnce sync.Oncefunc main() { chopsticks := make([]sync.Mutex, 5) permissionChannel := make(chan bool) finishEating := make(chan bool) go permissionFromHost(permissionChannel,finishEating) var wg sync.WaitGroup wg.Add(numOfPhilosophers) for i:=1 ; i<=numOfPhilosophers ; i++ { go eat(i, chopsticks[i-1], chopsticks[i%numOfPhilosophers], &wg, permissionChannel, finishEating) } wg.Wait()}func eat(philosopherId int, left sync.Mutex, right sync.Mutex, wg *sync.WaitGroup, permissionChannel <-chan bool, finishEatingChannel chan<- bool) { defer wg.Done() for i:=1 ; i<=numOfMeals ; i++ { //lock chopsticks in random order if RandBool() { left.Lock() right.Lock() } else { right.Lock() left.Lock() } fmt.Printf("waiting for permission from host %d\n",philosopherId) <-permissionChannel fmt.Printf("starting to eat %d (time %d)\n", philosopherId, i) fmt.Printf("finish to eat %d (time %d)\n", philosopherId, i) //release chopsticks left.Unlock() right.Unlock() //let host know I am done eating finishEatingChannel<-true }}func permissionFromHost(permissionChannel chan<-bool, finishEating <-chan bool) { ctr := 0 for { select { case <-finishEating: ctr-- default: if ctr<maxEaters { ctr++ permissionChannel<-true } } }}func RandBool() bool { rand.Seed(time.Now().UnixNano()) return rand.Intn(2) == 1}編輯1：我修復(fù)了通過(guò)引用傳遞的互斥體。它沒(méi)有解決問(wèn)題。編輯2：我試圖使用緩沖通道，使其工作permissionChannel:=make(chan bool, numOfPhilosophers)編輯3：也@Jaroslaw例子使它工作
2 回答
蠱毒傳說(shuō)
TA貢獻(xiàn)1895條經(jīng)驗(yàn) 獲得超3個(gè)贊
最后一個(gè) goroutine 不會(huì)退出，當(dāng)它寫入通道時(shí)，它將在最后一次迭代中被阻止，因?yàn)樗鼪](méi)有消費(fèi)者。沒(méi)有消費(fèi)者的原因是函數(shù)中的選擇情況正在寫入，但沒(méi)有消費(fèi)者，因?yàn)樗诘却蛔x取，所以我們有一個(gè)死鎖。finishEatingChannelfinishEatingChannelpermissionFromHostpermissionChannel<-truepermissionChannel
您可以使權(quán)限從主機(jī)通道緩沖，它將解決此問(wèn)題。
您的代碼中還有一個(gè)錯(cuò)誤，您正在按值傳遞互斥體，這是不允許的
慕后森
TA貢獻(xiàn)1802條經(jīng)驗(yàn) 獲得超5個(gè)贊
該命令說(shuō)go vet
./main.go:26:13: call of eat copies lock value: sync.Mutex
./main.go:26:30: call of eat copies lock value: sync.Mutex
./main.go:31:34: eat passes lock by value: sync.Mutex
./main.go:31:52: eat passes lock by value: sync.Mutex
另一個(gè)問(wèn)題是，有時(shí) goroutines（哲學(xué)家）在嘗試發(fā)送確認(rèn)時(shí)會(huì)被阻止，因?yàn)樨?fù)責(zé)從此無(wú)緩沖通道讀取數(shù)據(jù)的 goroutine（主機(jī)）正忙于嘗試發(fā)送權(quán)限。以下是代碼的確切部分：finishEatingChannel
if ctr<maxEaters {
ctr++
// This goroutine stucks since the last philosopher is not reading from permissionChannel.
// Philosopher is not reading from this channel at is busy trying to write finishEating channel which is not read by this goroutine.
// Thus the deadlock happens.
permissionChannel<-true
}
死鎖是100%可重復(fù)的，當(dāng)只剩下一個(gè)哲學(xué)家需要吃兩次飯時(shí)。
固定版本的代碼：
package main
import (
"fmt"
"math/rand"
"sync"
"time"
)
const (
numOfPhilosophers = 5
numOfMeals = 3
maxEaters = 2
)
func main() {
chopsticks := make([]sync.Mutex, 5)
permissionChannel := make(chan bool)
finishEating := make(chan bool)
go permissionFromHost(permissionChannel, finishEating)
var wg sync.WaitGroup
wg.Add(numOfPhilosophers)
for i := 1; i <= numOfPhilosophers; i++ {
go eat(i, &chopsticks[i-1], &chopsticks[i%numOfPhilosophers], &wg, permissionChannel, finishEating)
}
wg.Wait()
}
func eat(philosopherId int, left *sync.Mutex, right *sync.Mutex, wg *sync.WaitGroup, permissionChannel <-chan bool, finishEatingChannel chan<- bool) {
defer wg.Done()
for i := 1; i <= numOfMeals; i++ {
//lock chopsticks in random order
if RandBool() {
left.Lock()
right.Lock()
} else {
right.Lock()
left.Lock()
}
fmt.Printf("waiting for permission from host %d\n", philosopherId)
<-permissionChannel
fmt.Printf("starting to eat %d (time %d)\n", philosopherId, i)
fmt.Printf("finish to eat %d (time %d)\n", philosopherId, i)
//release chopsticks
left.Unlock()
right.Unlock()
//let host know I am done eating
finishEatingChannel <- true
}
}
func permissionFromHost(permissionChannel chan<- bool, finishEating <-chan bool) {
ctr := 0
for {
if ctr < maxEaters {
select {
case <-finishEating:
ctr--
case permissionChannel <- true:
ctr++
}
} else {
<-finishEating
ctr--
}
}
}
func RandBool() bool {
rand.Seed(time.Now().UnixNano())
return rand.Intn(2) == 1
}
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