runtime: more chan tests

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/57390043

src/pkg/runtime/chan_test.go

@@ -9,8 +9,327 @@ import (
 	"sync"
 	"sync/atomic"
 	"testing"
+	"time"
 )
 
+func TestChan(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
+	N := 200
+	if testing.Short() {
+		N = 20
+	}
+	for chanCap := 0; chanCap < N; chanCap++ {
+		{
+			// Ensure that receive from empty chan blocks.
+			c := make(chan int, chanCap)
+			recv1 := false
+			go func() {
+				_ = <-c
+				recv1 = true
+			}()
+			recv2 := false
+			go func() {
+				_, _ = <-c
+				recv2 = true
+			}()
+			time.Sleep(time.Millisecond)
+			if recv1 || recv2 {
+				t.Fatalf("chan[%d]: receive from empty chan", chanCap)
+			}
+			// Ensure that non-blocking receive does not block.
+			select {
+			case _ = <-c:
+				t.Fatalf("chan[%d]: receive from empty chan", chanCap)
+			default:
+			}
+			select {
+			case _, _ = <-c:
+				t.Fatalf("chan[%d]: receive from empty chan", chanCap)
+			default:
+			}
+			c <- 0
+			c <- 0
+		}
+
+		{
+			// Ensure that send to full chan blocks.
+			c := make(chan int, chanCap)
+			for i := 0; i < chanCap; i++ {
+				c <- i
+			}
+			sent := uint32(0)
+			go func() {
+				c <- 0
+				atomic.StoreUint32(&sent, 1)
+			}()
+			time.Sleep(time.Millisecond)
+			if atomic.LoadUint32(&sent) != 0 {
+				t.Fatalf("chan[%d]: send to full chan", chanCap)
+			}
+			// Ensure that non-blocking send does not block.
+			select {
+			case c <- 0:
+				t.Fatalf("chan[%d]: send to full chan", chanCap)
+			default:
+			}
+			<-c
+		}
+
+		{
+			// Ensure that we receive 0 from closed chan.
+			c := make(chan int, chanCap)
+			for i := 0; i < chanCap; i++ {
+				c <- i
+			}
+			close(c)
+			for i := 0; i < chanCap; i++ {
+				v := <-c
+				if v != i {
+					t.Fatalf("chan[%d]: received %v, expected %v", chanCap, v, i)
+				}
+			}
+			if v := <-c; v != 0 {
+				t.Fatalf("chan[%d]: received %v, expected %v", chanCap, v, 0)
+			}
+			if v, ok := <-c; v != 0 || ok {
+				t.Fatalf("chan[%d]: received %v/%v, expected %v/%v", chanCap, v, ok, 0, false)
+			}
+		}
+
+		{
+			// Ensure that close unblocks receive.
+			c := make(chan int, chanCap)
+			done := make(chan bool)
+			go func() {
+				v, ok := <-c
+				done <- v == 0 && ok == false
+			}()
+			time.Sleep(time.Millisecond)
+			close(c)
+			if !<-done {
+				t.Fatalf("chan[%d]: received non zero from closed chan", chanCap)
+			}
+		}
+
+		{
+			// Send 100 integers,
+			// ensure that we receive them non-corrupted in FIFO order.
+			c := make(chan int, chanCap)
+			go func() {
+				for i := 0; i < 100; i++ {
+					c <- i
+				}
+			}()
+			for i := 0; i < 100; i++ {
+				v := <-c
+				if v != i {
+					t.Fatalf("chan[%d]: received %v, expected %v", chanCap, v, i)
+				}
+			}
+
+			// Same, but using recv2.
+			go func() {
+				for i := 0; i < 100; i++ {
+					c <- i
+				}
+			}()
+			for i := 0; i < 100; i++ {
+				v, ok := <-c
+				if !ok {
+					t.Fatalf("chan[%d]: receive failed, expected %v", n, i)
+				}
+				if v != i {
+					t.Fatalf("chan[%d]: received %v, expected %v", n, v, i)
+				}
+			}
+
+			// Send 1000 integers in 4 goroutines,
+			// ensure that we receive what we send.
+			const P = 4
+			const L = 1000
+			for p := 0; p < P; p++ {
+				go func() {
+					for i := 0; i < L; i++ {
+						c <- i
+					}
+				}()
+			}
+			done := make(chan map[int]int)
+			for p := 0; p < P; p++ {
+				go func() {
+					recv := make(map[int]int)
+					for i := 0; i < L; i++ {
+						v := <-c
+						recv[v] = recv[v] + 1
+					}
+					done <- recv
+				}()
+			}
+			recv := make(map[int]int)
+			for p := 0; p < P; p++ {
+				for k, v := range <-done {
+					recv[k] = recv[k] + v
+				}
+			}
+			if len(recv) != L {
+				t.Fatalf("chan[%d]: received %v values, expected %v", n, len(recv), L)
+			}
+			for _, v := range recv {
+				if v != P {
+					t.Fatalf("chan[%d]: received %v values, expected %v", n, v, P)
+				}
+			}
+		}
+
+		{
+			// Test len/cap.
+			c := make(chan int, chanCap)
+			if len(c) != 0 || cap(c) != chanCap {
+				t.Fatalf("chan[%d]: bad len/cap, expect %v/%v, got %v/%v", chanCap, 0, chanCap, len(c), cap(c))
+			}
+			for i := 0; i < chanCap; i++ {
+				c <- i
+			}
+			if len(c) != chanCap || cap(c) != chanCap {
+				t.Fatalf("chan[%d]: bad len/cap, expect %v/%v, got %v/%v", chanCap, chanCap, chanCap, len(c), cap(c))
+			}
+		}
+
+	}
+}
+
+func TestSelfSelect(t *testing.T) {
+	// Ensure that send/recv on the same chan in select
+	// does not crash nor deadlock.
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
+	for _, chanCap := range []int{0, 10} {
+		var wg sync.WaitGroup
+		wg.Add(2)
+		c := make(chan int, chanCap)
+		for p := 0; p < 2; p++ {
+			p := p
+			go func() {
+				defer wg.Done()
+				for i := 0; i < 1000; i++ {
+					if p == 0 || i%2 == 0 {
+						select {
+						case c <- p:
+						case v := <-c:
+							if chanCap == 0 && v == p {
+								t.Fatalf("self receive")
+							}
+						}
+					} else {
+						select {
+						case v := <-c:
+							if chanCap == 0 && v == p {
+								t.Fatalf("self receive")
+							}
+						case c <- p:
+						}
+					}
+				}
+			}()
+		}
+		wg.Wait()
+	}
+}
+
+func TestSelectStress(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(10))
+	var c [4]chan int
+	c[0] = make(chan int)
+	c[1] = make(chan int)
+	c[2] = make(chan int, 2)
+	c[3] = make(chan int, 3)
+	N := int(1e5)
+	if testing.Short() {
+		N /= 10
+	}
+	// There are 4 goroutines that send N values on each of the chans,
+	// + 4 goroutines that receive N values on each of the chans,
+	// + 1 goroutine that sends N values on each of the chans in a single select,
+	// + 1 goroutine that receives N values on each of the chans in a single select.
+	// All these sends, receives and selects interact chaotically at runtime,
+	// but we are careful that this whole construct does not deadlock.
+	var wg sync.WaitGroup
+	wg.Add(10)
+	for k := 0; k < 4; k++ {
+		k := k
+		go func() {
+			for i := 0; i < N; i++ {
+				c[k] <- 0
+			}
+			wg.Done()
+		}()
+		go func() {
+			for i := 0; i < N; i++ {
+				<-c[k]
+			}
+			wg.Done()
+		}()
+	}
+	go func() {
+		var n [4]int
+		c1 := c
+		for i := 0; i < 4*N; i++ {
+			select {
+			case c1[3] <- 0:
+				n[3]++
+				if n[3] == N {
+					c1[3] = nil
+				}
+			case c1[2] <- 0:
+				n[2]++
+				if n[2] == N {
+					c1[2] = nil
+				}
+			case c1[0] <- 0:
+				n[0]++
+				if n[0] == N {
+					c1[0] = nil
+				}
+			case c1[1] <- 0:
+				n[1]++
+				if n[1] == N {
+					c1[1] = nil
+				}
+			}
+		}
+		wg.Done()
+	}()
+	go func() {
+		var n [4]int
+		c1 := c
+		for i := 0; i < 4*N; i++ {
+			select {
+			case <-c1[0]:
+				n[0]++
+				if n[0] == N {
+					c1[0] = nil
+				}
+			case <-c1[1]:
+				n[1]++
+				if n[1] == N {
+					c1[1] = nil
+				}
+			case <-c1[2]:
+				n[2]++
+				if n[2] == N {
+					c1[2] = nil
+				}
+			case <-c1[3]:
+				n[3]++
+				if n[3] == N {
+					c1[3] = nil
+				}
+			}
+		}
+		wg.Done()
+	}()
+	wg.Wait()
+}
+
 func TestChanSendInterface(t *testing.T) {
 	type mt struct{}
 	m := &mt{}
@@ -29,34 +348,35 @@ func TestChanSendInterface(t *testing.T) {
 
 func TestPseudoRandomSend(t *testing.T) {
 	n := 100
-	c := make(chan int)
-	l := make([]int, n)
-	var m sync.Mutex
-	m.Lock()
-	go func() {
+	for _, chanCap := range []int{0, n} {
+		c := make(chan int, chanCap)
+		l := make([]int, n)
+		var m sync.Mutex
+		m.Lock()
+		go func() {
+			for i := 0; i < n; i++ {
+				runtime.Gosched()
+				l[i] = <-c
+			}
+			m.Unlock()
+		}()
 		for i := 0; i < n; i++ {
-			runtime.Gosched()
-			l[i] = <-c
+			select {
+			case c <- 1:
+			case c <- 0:
+			}
 		}
-		m.Unlock()
-	}()
-	for i := 0; i < n; i++ {
-		select {
-		case c <- 0:
-		case c <- 1:
+		m.Lock() // wait
+		n0 := 0
+		n1 := 0
+		for _, i := range l {
+			n0 += (i + 1) % 2
+			n1 += i
 		}
-	}
-	m.Lock() // wait
-	n0 := 0
-	n1 := 0
-	for _, i := range l {
-		n0 += (i + 1) % 2
-		n1 += i
-		if n0 > n/10 && n1 > n/10 {
-			return
+		if n0 <= n/10 || n1 <= n/10 {
+			t.Errorf("Want pseudorandom, got %d zeros and %d ones (chan cap %d)", n0, n1, chanCap)
 		}
 	}
-	t.Errorf("Want pseudo random, got %d zeros and %d ones", n0, n1)
 }
 
 func TestMultiConsumer(t *testing.T) {