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// 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 (
"reflect"
"runtime"
. "sync"
"testing"
"time"
)
func TestCondSignal(t *testing.T) {
var m Mutex
c := NewCond(&m)
n := 2
running := make(chan bool, n)
awake := make(chan bool, n)
for i := 0; i < n; i++ {
go func() {
m.Lock()
running <- true
c.Wait()
awake <- true
m.Unlock()
}()
}
for i := 0; i < n; i++ {
<-running // Wait for everyone to run.
}
for n > 0 {
select {
case <-awake:
t.Fatal("goroutine not asleep")
default:
}
m.Lock()
c.Signal()
m.Unlock()
<-awake // Will deadlock if no goroutine wakes up
select {
case <-awake:
t.Fatal("too many goroutines awake")
default:
}
n--
}
c.Signal()
}
func TestCondSignalGenerations(t *testing.T) {
var m Mutex
c := NewCond(&m)
n := 100
running := make(chan bool, n)
awake := make(chan int, n)
for i := 0; i < n; i++ {
go func(i int) {
m.Lock()
running <- true
c.Wait()
awake <- i
m.Unlock()
}(i)
if i > 0 {
a := <-awake
if a != i-1 {
t.Fatalf("wrong goroutine woke up: want %d, got %d", i-1, a)
}
}
<-running
m.Lock()
c.Signal()
m.Unlock()
}
}
func TestCondBroadcast(t *testing.T) {
var m Mutex
c := NewCond(&m)
n := 200
running := make(chan int, n)
awake := make(chan int, n)
exit := false
for i := 0; i < n; i++ {
go func(g int) {
m.Lock()
for !exit {
running <- g
c.Wait()
awake <- g
}
m.Unlock()
}(i)
}
for i := 0; i < n; i++ {
for i := 0; i < n; i++ {
<-running // Will deadlock unless n are running.
}
if i == n-1 {
m.Lock()
exit = true
m.Unlock()
}
select {
case <-awake:
t.Fatal("goroutine not asleep")
default:
}
m.Lock()
c.Broadcast()
m.Unlock()
seen := make([]bool, n)
for i := 0; i < n; i++ {
g := <-awake
if seen[g] {
t.Fatal("goroutine woke up twice")
}
seen[g] = true
}
}
select {
case <-running:
t.Fatal("goroutine did not exit")
default:
}
c.Broadcast()
}
func TestRace(t *testing.T) {
x := 0
c := NewCond(&Mutex{})
done := make(chan bool)
go func() {
c.L.Lock()
x = 1
c.Wait()
if x != 2 {
t.Error("want 2")
}
x = 3
c.Signal()
c.L.Unlock()
done <- true
}()
go func() {
c.L.Lock()
for {
if x == 1 {
x = 2
c.Signal()
break
}
c.L.Unlock()
runtime.Gosched()
c.L.Lock()
}
c.L.Unlock()
done <- true
}()
go func() {
c.L.Lock()
for {
if x == 2 {
c.Wait()
if x != 3 {
t.Error("want 3")
}
break
}
if x == 3 {
break
}
c.L.Unlock()
runtime.Gosched()
c.L.Lock()
}
c.L.Unlock()
done <- true
}()
<-done
<-done
<-done
}
func TestCondSignalStealing(t *testing.T) {
for iters := 0; iters < 1000; iters++ {
var m Mutex
cond := NewCond(&m)
// Start a waiter.
ch := make(chan struct{})
go func() {
m.Lock()
ch <- struct{}{}
cond.Wait()
m.Unlock()
ch <- struct{}{}
}()
<-ch
m.Lock()
m.Unlock()
// We know that the waiter is in the cond.Wait() call because we
// synchronized with it, then acquired/released the mutex it was
// holding when we synchronized.
//
// Start two goroutines that will race: one will broadcast on
// the cond var, the other will wait on it.
//
// The new waiter may or may not get notified, but the first one
// has to be notified.
done := false
go func() {
cond.Broadcast()
}()
go func() {
m.Lock()
for !done {
cond.Wait()
}
m.Unlock()
}()
// Check that the first waiter does get signaled.
select {
case <-ch:
case <-time.After(2 * time.Second):
t.Fatalf("First waiter didn't get broadcast.")
}
// Release the second waiter in case it didn't get the
// broadcast.
m.Lock()
done = true
m.Unlock()
cond.Broadcast()
}
}
func TestCondCopy(t *testing.T) {
defer func() {
err := recover()
if err == nil || err.(string) != "sync.Cond is copied" {
t.Fatalf("got %v, expect sync.Cond is copied", err)
}
}()
c := Cond{L: &Mutex{}}
c.Signal()
var c2 Cond
reflect.ValueOf(&c2).Elem().Set(reflect.ValueOf(&c).Elem()) // c2 := c, hidden from vet
c2.Signal()
}
func BenchmarkCond1(b *testing.B) {
benchmarkCond(b, 1)
}
func BenchmarkCond2(b *testing.B) {
benchmarkCond(b, 2)
}
func BenchmarkCond4(b *testing.B) {
benchmarkCond(b, 4)
}
func BenchmarkCond8(b *testing.B) {
benchmarkCond(b, 8)
}
func BenchmarkCond16(b *testing.B) {
benchmarkCond(b, 16)
}
func BenchmarkCond32(b *testing.B) {
benchmarkCond(b, 32)
}
func benchmarkCond(b *testing.B, waiters int) {
c := NewCond(&Mutex{})
done := make(chan bool)
id := 0
for routine := 0; routine < waiters+1; routine++ {
go func() {
for i := 0; i < b.N; i++ {
c.L.Lock()
if id == -1 {
c.L.Unlock()
break
}
id++
if id == waiters+1 {
id = 0
c.Broadcast()
} else {
c.Wait()
}
c.L.Unlock()
}
c.L.Lock()
id = -1
c.Broadcast()
c.L.Unlock()
done <- true
}()
}
for routine := 0; routine < waiters+1; routine++ {
<-done
}
}