#golang #geektime

mutex.go

package main

import "time"
import "sync"
import "flag"
import "os"
import "log"
import "runtime"
import "runtime/pprof"
import "runtime/trace"
import "fmt"
import "testing"

var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to `file`")
var memprofile = flag.String("memprofile", "", "write memory profile to `file`")
var mutexprofile = flag.String("mutexprofile", "", "write memory profile to `file`")

func TestMutex(t *testing.T) {
	flag.Parse()

	f, _ := os.Create("trace.out")
	defer f.Close()
	trace.Start(f)
	defer trace.Stop()

	runtime.SetMutexProfileFraction(1)

	if *cpuprofile != "" {
		f, err := os.Create(*cpuprofile)
		if err != nil {
			log.Fatal("could not create CPU profile: ", err)
		}
		defer f.Close() // error handling omitted for example
		if err := pprof.StartCPUProfile(f); err != nil {
			log.Fatal("could not start CPU profile: ", err)
		}
		defer pprof.StopCPUProfile()
	}

	// ... rest of the program ...

	if *memprofile != "" {
		f, err := os.Create(*memprofile)
		if err != nil {
			log.Fatal("could not create memory profile: ", err)
		}
		defer f.Close() // error handling omitted for example
		runtime.GC()    // get up-to-date statistics
		if err := pprof.WriteHeapProfile(f); err != nil {
			log.Fatal("could not write memory profile: ", err)
		}
	}

	var acquired1 int
	var acquired2 int

	done := make(chan bool, 1)
	var mu sync.Mutex

	// goroutine1
	go func() {
		for {
			select {
			case <-done:
				return
			default:
				mu.Lock()
				acquired1++
				time.Sleep(100 * time.Microsecond)
				mu.Unlock()
			}
		}
	}()

	// goroutine2
	for i := 0; i < 1000; i++ {
		time.Sleep(100 * time.Microsecond)
		mu.Lock()
		acquired2++
		mu.Unlock()
	}
	done <- true
	fmt.Printf("mutex1 acquired times %d\n", acquired1)
	fmt.Printf("mutex2 acquired times %d\n", acquired2)
}