go waitgroup_test 源码
golang waitgroup_test 代码
文件路径：/src/sync/waitgroup_test.go
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sync_test
import (
. "sync"
"sync/atomic"
"testing"
)
func testWaitGroup(t *testing.T, wg1 *WaitGroup, wg2 *WaitGroup) {
n := 16
wg1.Add(n)
wg2.Add(n)
exited := make(chan bool, n)
for i := 0; i != n; i++ {
go func() {
wg1.Done()
wg2.Wait()
exited <- true
}()
}
wg1.Wait()
for i := 0; i != n; i++ {
select {
case <-exited:
t.Fatal("WaitGroup released group too soon")
default:
}
wg2.Done()
}
for i := 0; i != n; i++ {
<-exited // Will block if barrier fails to unlock someone.
}
}
func TestWaitGroup(t *testing.T) {
wg1 := &WaitGroup{}
wg2 := &WaitGroup{}
// Run the same test a few times to ensure barrier is in a proper state.
for i := 0; i != 8; i++ {
testWaitGroup(t, wg1, wg2)
}
}
func TestWaitGroupMisuse(t *testing.T) {
defer func() {
err := recover()
if err != "sync: negative WaitGroup counter" {
t.Fatalf("Unexpected panic: %#v", err)
}
}()
wg := &WaitGroup{}
wg.Add(1)
wg.Done()
wg.Done()
t.Fatal("Should panic")
}
func TestWaitGroupRace(t *testing.T) {
// Run this test for about 1ms.
for i := 0; i < 1000; i++ {
wg := &WaitGroup{}
n := new(int32)
// spawn goroutine 1
wg.Add(1)
go func() {
atomic.AddInt32(n, 1)
wg.Done()
}()
// spawn goroutine 2
wg.Add(1)
go func() {
atomic.AddInt32(n, 1)
wg.Done()
}()
// Wait for goroutine 1 and 2
wg.Wait()
if atomic.LoadInt32(n) != 2 {
t.Fatal("Spurious wakeup from Wait")
}
}
}
func TestWaitGroupAlign(t *testing.T) {
type X struct {
x byte
wg WaitGroup
}
var x X
x.wg.Add(1)
go func(x *X) {
x.wg.Done()
}(&x)
x.wg.Wait()
}
func BenchmarkWaitGroupUncontended(b *testing.B) {
type PaddedWaitGroup struct {
WaitGroup
pad [128]uint8
}
b.RunParallel(func(pb *testing.PB) {
var wg PaddedWaitGroup
for pb.Next() {
wg.Add(1)
wg.Done()
wg.Wait()
}
})
}
func benchmarkWaitGroupAddDone(b *testing.B, localWork int) {
var wg WaitGroup
b.RunParallel(func(pb *testing.PB) {
foo := 0
for pb.Next() {
wg.Add(1)
for i := 0; i < localWork; i++ {
foo *= 2
foo /= 2
}
wg.Done()
}
_ = foo
})
}
func BenchmarkWaitGroupAddDone(b *testing.B) {
benchmarkWaitGroupAddDone(b, 0)
}
func BenchmarkWaitGroupAddDoneWork(b *testing.B) {
benchmarkWaitGroupAddDone(b, 100)
}
func benchmarkWaitGroupWait(b *testing.B, localWork int) {
var wg WaitGroup
b.RunParallel(func(pb *testing.PB) {
foo := 0
for pb.Next() {
wg.Wait()
for i := 0; i < localWork; i++ {
foo *= 2
foo /= 2
}
}
_ = foo
})
}
func BenchmarkWaitGroupWait(b *testing.B) {
benchmarkWaitGroupWait(b, 0)
}
func BenchmarkWaitGroupWaitWork(b *testing.B) {
benchmarkWaitGroupWait(b, 100)
}
func BenchmarkWaitGroupActuallyWait(b *testing.B) {
b.ReportAllocs()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
var wg WaitGroup
wg.Add(1)
go func() {
wg.Done()
}()
wg.Wait()
}
})
}
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