With the following change:
https://code.google.com/p/go/source/detail?r=776aba85ece8d3c20c08641d28424be79fa0a1b0

os/exec test fails:
http://build.golang.org/log/91d335aeb85ff5f4855d3c168ca8dbe2da991f35

The problem is in exec_test.go:
        case "describefiles":
                for fd := uintptr(3); fd < 25; fd++ {
                        f := os.NewFile(fd, fmt.Sprintf("fd-%d", fd))
                        ln, err := net.FileListener(f)
                        if err == nil {
                                fmt.Printf("fd%d: listener %s\n", fd, ln.Addr())
                                ln.Close()
                        }
                }
                os.Exit(0)

This loop closes random file descriptors including netpoll kqueue descriptor.