Fix test_app task-tree

Executing `select {}` to wait forever triggers Go runtime deadlock
detection and kills the child, causing the number actual processes
be less than expected.

PiperOrigin-RevId: 376298799

pkg/test/testutil/BUILD

@@ -12,6 +12,7 @@ go_library(
     ],
     visibility = ["//:sandbox"],
     deps = [
+        "//pkg/sentry/watchdog",
         "//pkg/sync",
         "//runsc/config",
         "//runsc/specutils",

pkg/test/testutil/testutil.go

@@ -42,6 +42,7 @@ import (
 	"github.com/cenkalti/backoff"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sentry/watchdog"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/runsc/config"
 	"gvisor.dev/gvisor/runsc/specutils"
@@ -184,6 +185,7 @@ func TestConfig(t *testing.T) *config.Config {
 	conf.Network = config.NetworkNone
 	conf.Strace = true
 	conf.TestOnlyAllowRunAsCurrentUserWithoutChroot = true
+	conf.WatchdogAction = watchdog.Panic
 	return conf
 }
 

test/cmd/test_app/test_app.go

@@ -160,14 +160,17 @@ func (c *taskTree) SetFlags(f *flag.FlagSet) {
 
 // Execute implements subcommands.Command.
 func (c *taskTree) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
-	stop := testutil.StartReaper()
-	defer stop()
-
 	if c.depth == 0 {
 		log.Printf("Child sleeping, PID: %d\n", os.Getpid())
-		select {}
+		for {
+			time.Sleep(time.Hour)
+		}
 	}
-	log.Printf("Parent %d sleeping, PID: %d\n", c.depth, os.Getpid())
+
+	log.Printf("Parent %d creating %d children, PID: %d\n", c.depth, c.width, os.Getpid())
+
+	stop := testutil.StartReaper()
+	defer stop()
 
 	var cmds []*exec.Cmd
 	for i := 0; i < c.width; i++ {
@@ -175,7 +178,7 @@ func (c *taskTree) Execute(ctx context.Context, f *flag.FlagSet, args ...interfa
 			"/proc/self/exe", c.Name(),
 			"--depth", strconv.Itoa(c.depth-1),
 			"--width", strconv.Itoa(c.width),
-			"--pause", strconv.FormatBool(c.pause))
+			fmt.Sprintf("--pause=%t", c.pause))
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 
@@ -190,7 +193,10 @@ func (c *taskTree) Execute(ctx context.Context, f *flag.FlagSet, args ...interfa
 	}
 
 	if c.pause {
-		select {}
+		log.Printf("Parent %d sleeping, PID: %d\n", c.depth, os.Getpid())
+		for {
+			time.Sleep(time.Hour)
+		}
 	}
 
 	return subcommands.ExitSuccess