Re: [9fans] What is required of an open file to be used in ape/select?

Re: [9fans] What is required of an open file to be used in ape/select?

[bwc]

> I'm not convinced you want to go down this path.  It's
> almost always easier to use libthread and have separate
> procs reading from fds and passing data pointers back to a
> main proc.

I agree.  But I'm trying to write some stuff that will port
easily to Unix machines.

 Brantley

Re: [9fans] What is required of an open file to be used in ape/select?

[forsyth]

[-- Attachment #1: Type: text/plain, Size: 83 bytes --]

i did use it for that reason under second edition
and it worked as i expected.


[-- Attachment #2: Type: message/rfc822, Size: 1608 bytes --]

To: 9fans@cse.psu.edu
Subject: Re: [9fans] What is required of an open file to be used in ape/select?
Date: Tue, 9 Apr 2002 10:29:07 -0400
Message-ID: <20020409142546.E3C7919A7A@mail.cse.psu.edu>

> I'm not convinced you want to go down this path.  It's
> almost always easier to use libthread and have separate
> procs reading from fds and passing data pointers back to a
> main proc.

I agree.  But I'm trying to write some stuff that will port
easily to Unix machines.

 Brantley

Re: [9fans] What is required of an open file to be used in ape/select?

[Russ Cox]

> I have a server in user space that I mount on /n/ed.  It contains
> a file, /n/ed/cmsg.  What behavior must /n/ed/cmsg have to be
> useful with ape/select?  I wish to read when a control message arrives
> at the file.

I think that all files are equal in the eyes of ape select.
(Of course, it could be that select is broken and doesn't
work on any files.  I assume you tried selecting on
/n/ed/cmsg and it didn't work.)

I'm not convinced you want to go down this path.  It's
almost always easier to use libthread and have separate
procs reading from fds and passing data pointers back to a
main proc.

[addendum:]

Reading /n/ed/cmsg definitely needs to block until a control
message comes in.  This sometimes gets annoying because it
makes things like "cat /n/ed/cmsg" not as useful.  One sleazy
way around it is to keep track of whether you've returned eof
yet to this reader, and define that reads after one eof will block.
APE select doesn't give up reading the fd until it gets three eofs
(a heuristic to try to avoid problems with zero-length messages
in pipes).

Russ

Re: [9fans] What is required of an open file to be used in ape/select?

[Russ Cox]

> I have a server in user space that I mount on /n/ed.  It contains
> a file, /n/ed/cmsg.  What behavior must /n/ed/cmsg have to be
> useful with ape/select?  I wish to read when a control message arrives
> at the file.

I think that all files are equal in the eyes of ape select.
(Of course, it could be that select is broken and doesn't
work on any files.  I assume you tried selecting on
/n/ed/cmsg and it didn't work.)

I'm not convinced you want to go down this path.  It's
almost always easier to use libthread and have separate
procs reading from fds and passing data pointers back to a
main proc.

Russ

Re: [9fans] What is required of an open file to be used in ape/select?

[Boyd Roberts]

Russ Cox wrote:
> I'm not convinced you want to go down this path.  It's
> almost always easier to use libthread and have separate
> procs reading from fds and passing data pointers back to a
> main proc.

I'm with Russ on this one.

[9fans] What is required of an open file to be used in ape/select?

[bwc]

I have a server in user space that I mount on /n/ed.  It contains
a file, /n/ed/cmsg.  What behavior must /n/ed/cmsg have to be
useful with ape/select?  I wish to read when a control message arrives
at the file.

  Brantley Coile