NIO+Multithreaded TCPSocket listener, very low cpu utilisation

[kdevel]

On Wednesday, 15 November 2017 at 14:22:51 UTC, Daniel Kozak 
wrote:
> And this one
> https://paste.ofcode.org/KNqxcrmACLZLseB45MvwC

I thrash your code with two shell processes

```
     while true; do curl 127.0.0.1:4444 -o /dev/null; done
```

running parallel. Using strace -fFeclose on the binary this 
happens frequently:

```
:
[pid 10926] close(5)                    = 0
[pid 10926] close(4)                    = 0
[pid 10926] close(4)                    = 0
[pid 10926] close(4)                    = 0
[pid 10926] close(4)                    = 0
[pid 10926] --- SIGUSR1 (User defined signal 1) @ 0 (0) ---
[pid 10926] --- SIGUSR2 (User defined signal 2) @ 0 (0) ---
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
:
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
[pid 10919] close(4294967295)           = -1 EBADF (Bad file 
descriptor)
[pid 10926] close(4)                    = 0
[pid 10926] close(4)                    = 0
[pid 10926] close(4)                    = 0
:
```

The destructor of Socket is trying to close the already closed 
socket? If the worker I change

```
            socket.close();
```

to

```
             destroy (socket);
```

these close(-1) calls go away.