getcpu_amd64.s

// func GetCpuForThread() uint64
TEXT ·GetCpuForThread(SB),7,$0
	MOVQ $0xB,AX
	XORQ CX,CX
	CPUID
	MOVQ DX,ret+0(FP)
	RET

mutex.go

package mutex

import (
	"bytes"
	"fmt"
	"sync"
)

func GetCpuForThread() uint64

type InstrumentedMutex struct {
	sync.Mutex
	counts map[uint64]int
}

func (m *InstrumentedMutex) Lock() {
	m.Mutex.Lock()
	if m.counts == nil {
		m.counts = make(map[uint64]int)
	}
	m.counts[GetCpuForThread()]++
}

func (m *InstrumentedMutex) UnLock() {
	if m.counts == nil {
		m.counts = make(map[uint64]int)
	}
	m.counts[GetCpuForThread()]++
	m.Mutex.Unlock()
}

func (m *InstrumentedMutex) String() string {
	var buf bytes.Buffer
	for k, v := range m.counts {
		buf.WriteString(fmt.Sprintf("%2d: %d", k, v))
	}
	return buf.String()
}

mutex_test.go

package mutex

import (
	"runtime"
	"sync"
	"testing"
)

type counter struct {
	InstrumentedMutex
	count int
}

func (c *counter) Increment() {
	c.InstrumentedMutex.Lock()
	c.count++
	c.InstrumentedMutex.Unlock()
}

func work(c *counter, wg *sync.WaitGroup) {
	for i := 0; i < 100; i++ {
		c.Increment()
	}
	wg.Done()
}

func Test_Counter(t *testing.T) {
	runtime.GOMAXPROCS(runtime.NumCPU())
	var wg sync.WaitGroup
	var c counter
	for i := 0; i < 50; i++ {
		wg.Add(1)
		go work(&c, &wg)
	}
	wg.Wait()
	t.Log(c.String())
}

test_output.txt

$ go test -v
=== RUN Test_Counter
--- PASS: Test_Counter (0.00 seconds)
mutex_test.go:36: 	 0: 764 7: 194 3: 544 6: 821 2: 703 5: 494 1: 705 4: 775
PASS
ok  	_/Users/donovanhide/Desktop/4656676	0.024s