>> I couldn't see any harm in permitting TIOCSPGRP on ttys that aren't
>> your control tty, provided they aren't anyone else's either, [...]

[Jaromir]
> This looks okay. Does revoke(2) check (and remove) the O_ASYNC flag?

I don't think revoke() explicitly clears O_ASYNC/FASYNC.  However, I'm
not convinced it needs to; the flag on the file descriptor doesn't
matter - SIGIO is generated based on the TS_ASYNC flag on the tty.

[Christos]
> And you probably need to clear it when it joins a session too right?

The only place I can see that TS_ASYNC is cleared (besides userland
calling FIOASYNC or clearing O_ASYNC with F_SETFL) is ttyclose().

If a non-session tty has ASYNC set on it and it then, without being
ttyclose()d, becomes a session control terminal via TIOCSCTTY (which
appears to be the only way to set t_session to other than nil), it will
presently retain its ASYNC character...but TIOCSCTTY will bash t_pgrp,
so you're probably right.  (The only other place I can see t_pgrp being
set non-nil is TIOCSPGRP.  I wonder if that should clear TS_ASYNC too.)

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