Recover panic in udev goroutine

uevent.NewDecoder uses bufio.ReadString() that is blocking until data is available.
When booster switches to the userspace it needs to close all file descriptors
including the udev one.

Unfortunately there is no clear way to break the bufio.ReadString() blocking.
Attempt to close the fd causes panic inside the bufio.(*Reader).fill() function.

To prevent the app crash we just recover from panic in the udev goroutine.

Issue #22
Issue #31
Issue #153

Author: anatol

Diff for: init/udev.go

@@ -66,6 +66,15 @@ func validDmEvent(ev *uevent.Uevent) bool {
 var udevReader io.ReadCloser
 
 func udevListener() error {
+	defer func() {
+		// uevent.NewDecoder uses bufio.ReadString() that is blocking. If we try to close the underlying udev file descriptor
+		// while bufio tries to read from it then bufio panics. See issues #22, #31 and #153
+		// There is no clear way to prevent the panic so we just recover from it here and then safely exit the goroutine.
+		if r := recover(); r != nil {
+			warning("recovered udevListener panic: %v", r)
+		}
+	}()
+
 	var err error
 	udevReader, err = uevent.NewReader()
 	if err != nil {