implement SafeWaitGroup without race issue

This commit is contained in:
hzxuzhonghu 2017-11-02 19:25:35 +08:00
parent b47e0f8399
commit 6bca31cb49
4 changed files with 286 additions and 0 deletions

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load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
go_library(
name = "go_default_library",
srcs = [
"doc.go",
"waitgroup.go",
],
importpath = "k8s.io/apimachinery/pkg/util/waitgroup",
visibility = ["//visibility:public"],
)
go_test(
name = "go_default_test",
srcs = ["waitgroup_test.go"],
importpath = "k8s.io/apimachinery/pkg/util/waitgroup",
library = ":go_default_library",
)
filegroup(
name = "package-srcs",
srcs = glob(["**"]),
tags = ["automanaged"],
visibility = ["//visibility:private"],
)
filegroup(
name = "all-srcs",
srcs = [":package-srcs"],
tags = ["automanaged"],
visibility = ["//visibility:public"],
)

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/*
Copyright 2017 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
// Package waitgroup implements SafeWaitGroup wrap of sync.WaitGroup.
// Add with positive delta when waiting will fail, to prevent sync.WaitGroup race issue.
package waitgroup // import "k8s.io/apimachinery/pkg/util/waitgroup"

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/*
Copyright 2017 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package waitgroup
import (
"fmt"
"sync"
)
// SafeWaitGroup must not be copied after first use.
type SafeWaitGroup struct {
wg sync.WaitGroup
mu sync.RWMutex
// wait indicate whether Wait is called, if true,
// then any Add with positive delta will return error.
wait bool
}
// Add adds delta, which may be negative, similar to sync.WaitGroup.
// If Add with a positive delta happens after Wait, it will return error,
// which prevent unsafe Add.
func (wg *SafeWaitGroup) Add(delta int) error {
wg.mu.RLock()
if wg.wait && delta > 0 {
return fmt.Errorf("Add with postive delta after Wait is forbidden")
}
wg.mu.RUnlock()
wg.wg.Add(delta)
return nil
}
// Done decrements the WaitGroup counter.
func (wg *SafeWaitGroup) Done() {
wg.wg.Done()
}
// Wait blocks until the WaitGroup counter is zero.
func (wg *SafeWaitGroup) Wait() {
wg.mu.Lock()
wg.wait = true
wg.mu.Unlock()
wg.wg.Wait()
}

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/*
Copyright 2017 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
// Package waitgroup test cases reference golang sync.WaitGroup https://golang.org/src/sync/waitgroup_test.go.
package waitgroup
import (
"runtime"
"sync/atomic"
"testing"
)
func TestWaitGroup(t *testing.T) {
wg1 := &SafeWaitGroup{}
wg2 := &SafeWaitGroup{}
n := 16
wg1.Add(n)
wg2.Add(n)
exited := make(chan bool, n)
for i := 0; i != n; i++ {
go func(i int) {
wg1.Done()
wg2.Wait()
exited <- true
}(i)
}
wg1.Wait()
for i := 0; i != n; i++ {
select {
case <-exited:
t.Fatal("SafeWaitGroup released group too soon")
default:
}
wg2.Done()
}
for i := 0; i != n; i++ {
<-exited // Will block if barrier fails to unlock someone.
}
}
func TestWaitGroupNegativeCounter(t *testing.T) {
defer func() {
err := recover()
if err != "sync: negative WaitGroup counter" {
t.Fatalf("Unexpected panic: %#v", err)
}
}()
wg := &SafeWaitGroup{}
wg.Add(1)
wg.Done()
wg.Done()
t.Fatal("Should panic")
}
func TestWaitGroupAddFail(t *testing.T) {
wg := &SafeWaitGroup{}
wg.Add(1)
wg.Done()
wg.Wait()
if err := wg.Add(1); err == nil {
t.Errorf("Should return error when add positive after Wait")
}
}
func BenchmarkWaitGroupUncontended(b *testing.B) {
type PaddedWaitGroup struct {
SafeWaitGroup
pad [128]uint8
}
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
for p := 0; p < procs; p++ {
go func() {
var wg PaddedWaitGroup
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
wg.Add(1)
wg.Done()
}
}
c <- true
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func benchmarkWaitGroupAddDone(b *testing.B, localWork int) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
var wg SafeWaitGroup
for p := 0; p < procs; p++ {
go func() {
foo := 0
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
wg.Add(1)
for i := 0; i < localWork; i++ {
foo *= 2
foo /= 2
}
wg.Done()
}
}
c <- foo == 42
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func BenchmarkWaitGroupAddDone(b *testing.B) {
benchmarkWaitGroupAddDone(b, 0)
}
func BenchmarkWaitGroupAddDoneWork(b *testing.B) {
benchmarkWaitGroupAddDone(b, 100)
}
func benchmarkWaitGroupWait(b *testing.B, localWork int) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
var wg SafeWaitGroup
wg.Add(procs)
for p := 0; p < procs; p++ {
go wg.Done()
}
for p := 0; p < procs; p++ {
go func() {
foo := 0
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
wg.Wait()
for i := 0; i < localWork; i++ {
foo *= 2
foo /= 2
}
}
}
c <- foo == 42
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func BenchmarkWaitGroupWait(b *testing.B) {
benchmarkWaitGroupWait(b, 0)
}
func BenchmarkWaitGroupWaitWork(b *testing.B) {
benchmarkWaitGroupWait(b, 100)
}