Fix sff panic deadlock, share the evdev probe, assorted review cleanups

harness/main.go

@@ -46,6 +46,7 @@ func main() {
 	}
 
 	restoreTerm := rawKeys()
+	go relayStdin()
 
 	var err error
 	if *fuzzN > 0 {
@@ -84,6 +85,26 @@ func rawKeys() func() {
 	return func() { unix.IoctlSetTermios(fd, unix.TCSETS, &saved) }
 }
 
+// The child's own process group makes the tty off limits to it (reading from
+// the background raises SIGTTIN), so the harness reads and forwards to the
+// run that currently owns the console. One reader for the life of the
+// process: a copier per run would pile up under fuzz, each stealing
+// keystrokes for a run already gone.
+func relayStdin() {
+	buf := make([]byte, 64)
+	for {
+		n, err := os.Stdin.Read(buf)
+		if err != nil {
+			return
+		}
+		consoleMu.Lock()
+		if console != nil {
+			console.Write(buf[:n])
+		}
+		consoleMu.Unlock()
+	}
+}
+
 func fuzz(n int, runFor time.Duration, args []string) error {
 	failed := 0
 	for i := 1; i <= n; i++ {
@@ -162,13 +183,10 @@ func run(runFor time.Duration, at string, out io.Writer, args []string) error {
 	// killed when go run dies, and an orphan holding the wire poisons every
 	// measurement after it.
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
-	// The child's own process group makes the tty off limits to it (reading
-	// from the background raises SIGTTIN), so the harness reads and forwards.
 	stdin, err := cmd.StdinPipe()
 	if err != nil {
 		return err
 	}
-	go io.Copy(stdin, os.Stdin)
 	consoleMu.Lock()
 	console = stdin
 	consoleMu.Unlock()