>> [I]t appears that fcntl(F_SETOWN) on anything but a socket
>> interprets a process ID (positive arg) as meaning "send SIGIO to the
>> whole process group this process belongs to", not the documented
>> behavior of sending SIGIO to (just) that process.

> This worked as intended last time I looked (when I tested SIGIO for
> NEW_PIPE).

What DTYPE_ are they?  If they're not DTYPE_SOCKET (which NEW_PIPE
pipes may be, for all I know), I suspect you just didn't test
thoroughly enough.

> Positive value is process ID, negative is -process_group.  At least
> it _appeared_ to be working for me.

Yes, but a process ID is silently converted to that process's process
group ID for everything that's not DTYPE_SOCKET.  Read the code at case
F_SETOWN in kern/kern_descrip.c....

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