ci: fix a race in TestExecIn and TestExecInTTY

Fixes: #4437
We can use a chan to wait the output from init process. After we received the content,
it means that the init process has started. Then we can exec into this container to use
ps command to check the init process and the exec process are both exist.

Signed-off-by: lifubang <lifubang@acmcoder.com>

Author: lifubang

libcontainer/integration/execin_test.go

@@ -30,16 +30,37 @@ func TestExecIn(t *testing.T) {
 	// Execute a first process in the container
 	stdinR, stdinW, err := os.Pipe()
 	ok(t, err)
+	defer func() {
+		_ = stdinR.Close()
+		_ = stdinW.Close()
+	}()
+	stdoutR, stdoutW, err := os.Pipe()
+	ok(t, err)
+	defer func() {
+		_ = stdoutR.Close()
+		_ = stdoutW.Close()
+	}()
+
+	ch := waitStdOut(stdoutR)
 	process := &libcontainer.Process{
-		Cwd:   "/",
-		Args:  []string{"cat"},
-		Env:   standardEnvironment,
-		Stdin: stdinR,
-		Init:  true,
+		Cwd:    "/",
+		Args:   []string{"cat", "/proc/self/cmdline", "-"},
+		Env:    standardEnvironment,
+		Stdin:  stdinR,
+		Stdout: stdoutW,
+		Init:   true,
 	}
 	err = container.Run(process)
-	_ = stdinR.Close()
-	defer stdinW.Close() //nolint: errcheck
+	defer func() {
+		_, _ = stdinW.Write([]byte("hello"))
+		_ = stdinW.Close()
+		if _, err := process.Wait(); err != nil {
+			t.Log(err)
+		}
+	}()
+	ok(t, err)
+
+	err = <-ch
 	ok(t, err)
 
 	buffers := newStdBuffers()
@@ -55,8 +76,6 @@ func TestExecIn(t *testing.T) {
 	err = container.Run(ps)
 	ok(t, err)
 	waitProcess(ps, t)
-	_ = stdinW.Close()
-	waitProcess(process, t)
 
 	out := buffers.Stdout.String()
 	if !strings.Contains(out, "cat") || !strings.Contains(out, "ps") {
@@ -242,23 +261,39 @@ func TestExecInTTY(t *testing.T) {
 	// Execute a first process in the container
 	stdinR, stdinW, err := os.Pipe()
 	ok(t, err)
+	defer func() {
+		_ = stdinR.Close()
+		_ = stdinW.Close()
+	}()
+	stdoutR, stdoutW, err := os.Pipe()
+	ok(t, err)
+	defer func() {
+		_ = stdoutR.Close()
+		_ = stdoutW.Close()
+	}()
+
+	ch := waitStdOut(stdoutR)
 	process := &libcontainer.Process{
-		Cwd:   "/",
-		Args:  []string{"cat"},
-		Env:   standardEnvironment,
-		Stdin: stdinR,
-		Init:  true,
+		Cwd:    "/",
+		Args:   []string{"cat", "/proc/self/cmdline", "-"},
+		Env:    standardEnvironment,
+		Stdin:  stdinR,
+		Stdout: stdoutW,
+		Init:   true,
 	}
 	err = container.Run(process)
-	_ = stdinR.Close()
 	defer func() {
+		_, _ = stdinW.Write([]byte("hello"))
 		_ = stdinW.Close()
 		if _, err := process.Wait(); err != nil {
 			t.Log(err)
 		}
 	}()
 	ok(t, err)
 
+	err = <-ch
+	ok(t, err)
+
 	ps := &libcontainer.Process{
 		Cwd:  "/",
 		Args: []string{"ps"},

libcontainer/integration/utils_test.go

@@ -231,3 +231,25 @@ func runContainerOk(t *testing.T, config *configs.Config, args ...string) *stdBu
 func destroyContainer(container *libcontainer.Container) {
 	_ = container.Destroy()
 }
+
+func waitStdOut(stdout *os.File) chan error {
+	ch := make(chan error, 1)
+	buf := make([]byte, 1)
+	go func() {
+		defer close(ch)
+
+		for {
+			n, err := stdout.Read(buf)
+			if err != nil {
+				ch <- err
+				return
+			}
+
+			if n >= 0 {
+				ch <- nil
+				return
+			}
+		}
+	}()
+	return ch
+}