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// Copyright 2012 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 race_test
import (
"runtime"
"sync"
"testing"
"time"
)
func TestNoRaceWaitGroup(t *testing.T) {
var x int
var wg sync.WaitGroup
n := 1
for i := 0; i < n; i++ {
wg.Add(1)
j := i
go func() {
x = j
wg.Done()
}()
}
wg.Wait()
}
func TestRaceWaitGroup(t *testing.T) {
var x int
var wg sync.WaitGroup
n := 2
for i := 0; i < n; i++ {
wg.Add(1)
j := i
go func() {
x = j
wg.Done()
}()
}
wg.Wait()
}
func TestNoRaceWaitGroup2(t *testing.T) {
var x int
var wg sync.WaitGroup
wg.Add(1)
go func() {
x = 1
wg.Done()
}()
wg.Wait()
x = 2
}
// incrementing counter in Add and locking wg's mutex
func TestRaceWaitGroupAsMutex(t *testing.T) {
var x int
var wg sync.WaitGroup
c := make(chan bool, 2)
go func() {
wg.Wait()
time.Sleep(100 * time.Millisecond)
wg.Add(+1)
x = 1
wg.Add(-1)
c <- true
}()
go func() {
wg.Wait()
time.Sleep(100 * time.Millisecond)
wg.Add(+1)
x = 2
wg.Add(-1)
c <- true
}()
<-c
<-c
}
// Incorrect usage: Add is too late.
func TestRaceWaitGroupWrongWait(t *testing.T) {
c := make(chan bool, 2)
var x int
var wg sync.WaitGroup
go func() {
wg.Add(1)
runtime.Gosched()
x = 1
wg.Done()
c <- true
}()
go func() {
wg.Add(1)
runtime.Gosched()
x = 2
wg.Done()
c <- true
}()
wg.Wait()
<-c
<-c
}
// A common WaitGroup misuse that can potentially be caught be the race detector.
// For this simple case we must emulate Add() as read on &wg and Wait() as write on &wg.
// However it will have false positives if there are several concurrent Wait() calls.
func TestRaceFailingWaitGroupWrongAdd(t *testing.T) {
c := make(chan bool, 2)
var wg sync.WaitGroup
go func() {
wg.Add(1)
wg.Done()
c <- true
}()
go func() {
wg.Add(1)
wg.Done()
c <- true
}()
wg.Wait()
<-c
<-c
}
func TestNoRaceWaitGroupMultipleWait(t *testing.T) {
c := make(chan bool, 2)
var wg sync.WaitGroup
go func() {
wg.Wait()
c <- true
}()
go func() {
wg.Wait()
c <- true
}()
wg.Wait()
<-c
<-c
}
func TestNoRaceWaitGroupMultipleWait2(t *testing.T) {
c := make(chan bool, 2)
var wg sync.WaitGroup
wg.Add(2)
go func() {
wg.Done()
wg.Wait()
c <- true
}()
go func() {
wg.Done()
wg.Wait()
c <- true
}()
wg.Wait()
<-c
<-c
}
// Correct usage but still a race
func TestRaceWaitGroup2(t *testing.T) {
var x int
var wg sync.WaitGroup
wg.Add(2)
go func() {
x = 1
wg.Done()
}()
go func() {
x = 2
wg.Done()
}()
wg.Wait()
}
func TestNoRaceWaitGroupPanicRecover(t *testing.T) {
var x int
var wg sync.WaitGroup
defer func() {
err := recover()
if err != "sync: negative WaitGroup counter" {
t.Fatalf("Unexpected panic: %#v", err)
}
x = 2
}()
x = 1
wg.Add(-1)
}
// TODO: this is actually a panic-synchronization test, not a
// WaitGroup test. Move it to another *_test file
// Is it possible to get a race by synchronization via panic?
func TestNoRaceWaitGroupPanicRecover2(t *testing.T) {
var x int
var wg sync.WaitGroup
ch := make(chan bool, 1)
var f func() = func() {
x = 2
ch <- true
}
go func() {
defer func() {
err := recover()
if err != "sync: negative WaitGroup counter" {
}
go f()
}()
x = 1
wg.Add(-1)
}()
<-ch
}
func TestNoRaceWaitGroupTransitive(t *testing.T) {
x, y := 0, 0
var wg sync.WaitGroup
wg.Add(2)
go func() {
x = 42
wg.Done()
}()
go func() {
time.Sleep(1e7)
y = 42
wg.Done()
}()
wg.Wait()
_ = x
_ = y
}
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