mutexes _ golang

In the previous example we saw how to manage simple counter state using atomic operations. For more complex state we can use a mutex to safetly access data across multiple goroutines

package main

import (
    "fmt"
    "math/rand"
    "runtime"
    "sync"
    "sync/atomic"
    "time"
)

func main() {

    var state = make(map[int]int)

    var mutex = &sync.Mutex{}

    var ops int64 = 0

    for r := 0; r <= 100; r++ {
        go func() {
            total := 0
            for {
                key := rand.Intn(5)
                mutex.Lock()
                total += state[key]
                mutex.Unlock()
                atomic.AddInt64(&ops, 1)

                runtime.Gosched()
            }
        }()
    }

    for w := 0; w < 10; w++ {
        go func() {
            for {
                key := rand.Intn(5)
                val := rand.Intn(100)
                mutex.Lock()
                state[key] = val
                mutex.Unlock()
                atomic.AddInt64(&ops, 1)
                runtime.Gosched()
            }
        }()
    }

    time.Sleep(time.Second)

    opsFinal := atomic.LoadInt64(&ops)

    fmt.Println("ops: ", opsFinal)

    mutex.Lock()
    fmt.Println("state :", state)
    mutex.Unlock()
}

ops:  4738109
state : map[0:40 2:43 3:90 1:13 4:7]

总结 :

　　1: ...