Golang Mutex.Lock方法代碼示例

func (cmd *serveEmbedCmd) run(ctx scope.Context, args []string) error {
	listener, err := net.Listen("tcp", cmd.addr)
	if err != nil {
		return err
	}

	closed := false
	m := sync.Mutex{}
	closeListener := func() {
		m.Lock()
		if !closed {
			listener.Close()
			closed = true
		}
		m.Unlock()
	}

	// Spin off goroutine to watch ctx and close listener if shutdown requested.
	go func() {
		<-ctx.Done()
		closeListener()
	}()

	if err := http.Serve(listener, cmd); err != nil {
		fmt.Printf("http[%s]: %s\n", cmd.addr, err)
		return err
	}

	closeListener()
	ctx.WaitGroup().Done()
	return ctx.Err()
}

// Run runs the query concurrently, and returns the results.
func (q *Query) Run() []interface{} {
	rand.Seed(time.Now().UnixNano())
	var w sync.WaitGroup
	var l sync.Mutex
	places := make([]interface{}, len(q.Journey))
	for i, r := range q.Journey {
		w.Add(1)
		go func(types string, i int) {
			defer w.Done()
			response, err := q.find(types)
			if err != nil {
				log.Println("Failed to find places:", err)
				return
			}
			if len(response.Results) == 0 {
				log.Println("No places found for", types)
				return
			}
			for _, result := range response.Results {
				for _, photo := range result.Photos {
					photo.URL = "https://maps.googleapis.com/maps/api/place/photo?" +
						"maxwidth=1000&photoreference=" + photo.PhotoRef + "&key=" + APIKey
				}
			}
			randI := rand.Intn(len(response.Results))
			l.Lock()
			places[i] = response.Results[randI]
			l.Unlock()
		}(r, i)
	}
	w.Wait() // wait for everything to finish
	return places
}

// Put implements the Putter interface.
func (mp *MultiPutter) Put(username string, creds map[string]interface{}) error {
	var (
		err error
		mu  sync.Mutex
		wg  sync.WaitGroup
	)

	for _, p := range mp.Putters {
		wg.Add(1)

		go func(p Putter) {
			defer wg.Done()

			if e := p.Put(username, creds); e != nil {
				mu.Lock()
				err = multierror.Append(err, e)
				mu.Unlock()
			}
		}(p)
	}

	wg.Wait()

	return err
}

// GetLookupdTopicChannels returns a []string containing a union of the channels
// from all the given lookupd for the given topic
func GetLookupdTopicChannels(topic string, lookupdHTTPAddrs []string) ([]string, error) {
	success := false
	allChannels := make([]string, 0)
	var lock sync.Mutex
	var wg sync.WaitGroup
	for _, addr := range lookupdHTTPAddrs {
		wg.Add(1)
		endpoint := fmt.Sprintf("http://%s/channels?topic=%s", addr, url.QueryEscape(topic))
		log.Printf("LOOKUPD: querying %s", endpoint)
		go func(endpoint string) {
			data, err := util.ApiRequest(endpoint)
			lock.Lock()
			defer lock.Unlock()
			defer wg.Done()
			if err != nil {
				log.Printf("ERROR: lookupd %s - %s", endpoint, err.Error())
				return
			}
			success = true
			// {"data":{"channels":["test"]}}
			channels, _ := data.Get("channels").StringArray()
			allChannels = util.StringUnion(allChannels, channels)
		}(endpoint)
	}
	wg.Wait()
	sort.Strings(allChannels)
	if success == false {
		return nil, errors.New("unable to query any lookupd")
	}
	return allChannels, nil
}

func (a *apiServer) runPipeline(pipelineInfo *pps.PipelineInfo) error {
	ctx, cancel := context.WithCancel(context.Background())
	a.lock.Lock()
	a.cancelFuncs[*pipelineInfo.Pipeline] = cancel
	a.lock.Unlock()
	var loopErr error
	//TODO this gets really weird with branching... we need to figure out what that looks like.
	mostRecentCommit := make(map[pfs.Repo]*pfs.Commit)
	var lock sync.Mutex
	var wg sync.WaitGroup
	for _, inputRepo := range pipelineInfo.InputRepo {
		inputRepo := inputRepo
		wg.Add(1)
		go func() {
			defer wg.Done()
			var lastCommit *pfs.Commit
			listCommitRequest := &pfs.ListCommitRequest{
				Repo:       inputRepo,
				CommitType: pfs.CommitType_COMMIT_TYPE_READ,
				From:       lastCommit,
				Block:      true,
			}
			commitInfos, err := a.pfsAPIClient.ListCommit(ctx, listCommitRequest)
			if err != nil && loopErr == nil {
				loopErr = err
				return
			}
			for _, commitInfo := range commitInfos.CommitInfo {
				lock.Lock()
				mostRecentCommit[*inputRepo] = commitInfo.Commit
				var commits []*pfs.Commit
				for _, commit := range mostRecentCommit {
					commits = append(commits, commit)
				}
				lock.Unlock()
				if len(commits) < len(pipelineInfo.InputRepo) {
					// we don't yet have a commit for every input repo so there's no way to run the job
					continue
				}
				outParentCommit, err := a.bestParent(pipelineInfo, commitInfo)
				if err != nil && loopErr == nil {
					loopErr = err
					return
				}
				_, err = a.jobAPIClient.CreateJob(
					ctx,
					&pps.CreateJobRequest{
						Spec: &pps.CreateJobRequest_Pipeline{
							Pipeline: pipelineInfo.Pipeline,
						},
						InputCommit:  []*pfs.Commit{commitInfo.Commit},
						OutputParent: outParentCommit,
					},
				)
			}
		}()
	}
	wg.Wait()
	return loopErr
}

// NewAddresses fetches EC2 IP address list from each region.
//
// If log is nil, defaultLogger is used instead.
func NewAddresses(clients *amazon.Clients, log logging.Logger) *Addresses {
	if log == nil {
		log = defaultLogger
	}
	a := newAddresses()
	var wg sync.WaitGroup
	var mu sync.Mutex // protects a.m
	for region, client := range clients.Regions() {
		wg.Add(1)
		go func(region string, client *amazon.Client) {
			defer wg.Done()
			addresses, err := client.Addresses()
			if err != nil {
				log.Error("[%s] fetching IP addresses error: %s", region, err)
				return
			}
			log.Info("[%s] fetched %d addresses", region, len(addresses))
			var ok bool
			mu.Lock()
			if _, ok = a.m[client]; !ok {
				a.m[client] = addresses
			}
			mu.Unlock()
			if ok {
				panic(fmt.Errorf("[%s] duplicated client=%p: %+v", region, client, addresses))
			}
		}(region, client)
	}
	wg.Wait()
	return a
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU()) // 모든 CPU 사용

	var mutex = new(sync.Mutex)    // 뮤텍스 생성
	var cond = sync.NewCond(mutex) // 뮤텍스를 이용하여 조건 변수 생성

	c := make(chan bool, 3) // 비동기 채널 생성

	for i := 0; i < 3; i++ {
		go func(n int) { // 고루틴 3개 생성
			mutex.Lock() // 뮤텍스 잠금, cond.Wait() 보호 시작
			c <- true    // 채널 c에 true를 보냄
			fmt.Println("wait begin : ", n)
			cond.Wait() // 조건 변수 대기
			fmt.Println("wait end : ", n)
			mutex.Unlock() // 뮤텍스 잠금 해제, cond.Wait() 보호 종료

		}(i)
	}

	for i := 0; i < 3; i++ {
		<-c // 채널에서 값을 꺼냄, 고루틴 3개가 모두 실행될 때까지 기다림
	}

	for i := 0; i < 3; i++ {
		mutex.Lock() // 뮤텍스 잠금, cond.Signal() 보호 시작
		fmt.Println("signal : ", i)
		cond.Signal()  // 대기하고 있는 고루틴을 하나씩 깨움
		mutex.Unlock() // 뮤텍스 잠금 해제, cond.Signal() 보고 종료
	}

	fmt.Scanln()
}

func benchmarkMutexLock(b *testing.B) {
	var lock sync.Mutex
	for i := 0; i < b.N; i++ {
		lock.Lock()
		lock.Unlock()
	}
}

func TestPseudoRandomSend(t *testing.T) {
	n := 100
	for _, chanCap := range []int{0, n} {
		c := make(chan int, chanCap)
		l := make([]int, n)
		var m sync.Mutex
		m.Lock()
		go func() {
			for i := 0; i < n; i++ {
				runtime.Gosched()
				l[i] = <-c
			}
			m.Unlock()
		}()
		for i := 0; i < n; i++ {
			select {
			case c <- 1:
			case c <- 0:
			}
		}
		m.Lock() // wait
		n0 := 0
		n1 := 0
		for _, i := range l {
			n0 += (i + 1) % 2
			n1 += i
		}
		if n0 <= n/10 || n1 <= n/10 {
			t.Errorf("Want pseudorandom, got %d zeros and %d ones (chan cap %d)", n0, n1, chanCap)
		}
	}
}

func main() {
	flag.Parse()

	if *zookeeper == "" {
		printUsageErrorAndExit("You have to provide a zookeeper connection string using -zookeeper, or the ZOOKEEPER_PEERS environment variable")
	}

	conf := kazoo.NewConfig()
	conf.Timeout = time.Duration(*zookeeperTimeout) * time.Millisecond

	kz, err := kazoo.NewKazooFromConnectionString(*zookeeper, conf)
	if err != nil {
		printErrorAndExit(69, "Failed to connect to Zookeeper: %v", err)
	}
	defer func() { _ = kz.Close() }()

	topics, err := kz.Topics()
	if err != nil {
		printErrorAndExit(69, "Failed to get Kafka topics from Zookeeper: %v", err)
	}
	sort.Sort(topics)

	var (
		wg     sync.WaitGroup
		l      sync.Mutex
		stdout = make([]string, len(topics))
	)

	for i, topic := range topics {
		wg.Add(1)
		go func(i int, topic *kazoo.Topic) {
			defer wg.Done()

			buffer := bytes.NewBuffer(make([]byte, 0))

			partitions, err := topic.Partitions()
			if err != nil {
				printErrorAndExit(69, "Failed to get Kafka topic partitions from Zookeeper: %v", err)
			}

			fmt.Fprintf(buffer, "Topic: %s\tPartitions: %d\n", topic.Name, len(partitions))

			for _, partition := range partitions {
				leader, _ := partition.Leader()
				isr, _ := partition.ISR()

				fmt.Fprintf(buffer, "\tPartition: %d\tReplicas: %v\tLeader: %d\tISR: %v\n", partition.ID, partition.Replicas, leader, isr)
			}

			l.Lock()
			stdout[i] = buffer.String()
			l.Unlock()
		}(i, topic)
	}

	wg.Wait()
	for _, msg := range stdout {
		fmt.Print(msg)
	}
}

func diameter(digests []string, diffStore diff.DiffStore) int {
	// TODO Parallelize.
	lock := sync.Mutex{}
	max := 0
	wg := sync.WaitGroup{}
	for {
		if len(digests) <= 2 {
			break
		}
		wg.Add(1)
		go func(d1 string, d2 []string) {
			defer wg.Done()
			dms, err := diffStore.Get(d1, d2)
			if err != nil {
				glog.Errorf("Unable to get diff: %s", err)
				return
			}
			localMax := 0
			for _, dm := range dms {
				if dm.NumDiffPixels > localMax {
					localMax = dm.NumDiffPixels
				}
			}
			lock.Lock()
			defer lock.Unlock()
			if localMax > max {
				max = localMax
			}
		}(digests[0], digests[1:2])
		digests = digests[1:]
	}
	wg.Wait()
	return max
}

func cacher(regMap map[*regexp.Regexp]string) func(string) string {
	var cache = make(map[string]string)
	var cacheMu sync.Mutex

	return func(ext string) string {
		cacheMu.Lock()
		defer cacheMu.Unlock()

		memoized, ok := cache[ext]
		if ok {
			return memoized
		}

		bExt := []byte(ext)
		for regEx, mimeType := range regMap {
			if regEx != nil && regEx.Match(bExt) {
				memoized = mimeType
				break
			}
		}

		cache[ext] = memoized
		return memoized
	}
}

// generic loop (executed in a goroutine) that periodically wakes up to walk
// the priority queue and call the callback
func (c *Channel) pqWorker(pq *pqueue.PriorityQueue, mutex *sync.Mutex, callback func(item *pqueue.Item)) {
	ticker := time.NewTicker(defaultWorkerWait)
	for {
		select {
		case <-ticker.C:
		case <-c.exitChan:
			goto exit
		}
		now := time.Now().UnixNano()
		for {
			mutex.Lock()
			item, _ := pq.PeekAndShift(now)
			mutex.Unlock()

			if item == nil {
				break
			}

			callback(item)
		}
	}

exit:
	log.Printf("CHANNEL(%s): closing ... pqueue worker", c.name)
	ticker.Stop()
}

func memoizeBytes() byteDescription {
	cache := map[int64]string{}
	suffixes := []string{"B", "KB", "MB", "GB", "TB", "PB"}
	maxLen := len(suffixes) - 1

	var cacheMu sync.Mutex

	return func(b int64) string {
		cacheMu.Lock()
		defer cacheMu.Unlock()

		description, ok := cache[b]
		if ok {
			return description
		}

		bf := float64(b)
		i := 0
		description = ""
		for {
			if bf/BytesPerKB < 1 || i >= maxLen {
				description = fmt.Sprintf("%.2f%s", bf, suffixes[i])
				break
			}
			bf /= BytesPerKB
			i += 1
		}
		cache[b] = description
		return description
	}
}

func main() {
	var mtx sync.Mutex
	var cnd *sync.Cond
	var cnds [N]*sync.Cond
	var mtxs [N]sync.Mutex
	cnd = sync.NewCond(&mtx)
	for i := 0; i < N; i++ {
		cnds[i] = sync.NewCond(&mtxs[i])
	}
	for i := 0; i < N; i++ {
		go func(me int, m *sync.Mutex, c1 *sync.Cond, c2 *sync.Cond) {
			fmt.Printf("Hello, world. %d\n", me)
			if me == 0 {
				cnd.Signal()
			}
			for j := 0; j < 10000000; j++ {
				m.Lock()
				c1.Wait()
				m.Unlock()
				c2.Signal()
			}
			if me == N-1 {
				cnd.Signal()
			}
		}(i, &mtxs[i], cnds[i], cnds[(i+1)%N])
	}
	mtx.Lock()
	cnd.Wait()
	mtx.Unlock()
	cnds[0].Signal()
	mtx.Lock()
	cnd.Wait()
	mtx.Unlock()
}