A hard-to-reproduce EPollSelector bug...

[Alan Bateman]

On 15/03/2018 21:01, David Lloyd wrote:
> :
> OK this is my understanding of what's happening.  I've chosen
> EPollSelectorImpl because I understand it most, though as I said we've
> seen this on other OSes: Mac, Windows (!), and Linux for certain.  I
> can't be 100% sure it's exactly the same problem but even if it isn't,
> the fix (manually awakening/selecting all associated selectors) solves
> the problem in every case.  Whether that's due to a coincidence of
> scheduling or some other secondary subtlety is hard to know.
ServerSocketChannel.bind didn't historically synchronize correctly on 
channel state and so could fail in interesting ways when called at 
around the same time that it is closed. Specifically it could attempt to 
bind after the dup2, or worse, after the file descriptor has been closed 
and recycled. If there were a T3 in the picture that was created a 
listener at around the same time then it might be possible to explain 
the EADDRINUSE.

-Alan