Single Evented on more than on Poll

[dtolnay]

Question from i.r-l.o:

Can a single Evented be registered on more than one Poll? What happens? The documentation doesn’t seem to clearly say anything.

[cramertj]

This comment in the Unix implementation says that only one poll registration per Evented is supported:

/// Each Selector has a globally unique(ish) ID associated with it. This ID
/// gets tracked by `TcpStream`, `TcpListener`, etc... when they are first
/// registered with the `Selector`. If a type that is previously associated with
/// a `Selector` attempts to register itself with a different `Selector`, the
/// operation will return with an error. This matches windows behavior.

[carllerche]

Yes, Evented values can only be registered with a single Poll instance ever (even if the value is deregistered). There are non-portable work arounds (like using a FD directly).