Re: [gentoo-portage-dev] EbuildProcess logs poll-error to already removed $T (on AIX)

[Zac Medico]

On 03/28/2011 03:05 AM, Michael Haubenwallner wrote:
>
>
> On 03/25/2011 05:23 PM, Zac Medico wrote:
>>>  * EbuildProcess received strange poll event: 16384
>
>> You can compare 16384 to the values of POLLERR and POLLNVAL in order to
>> see what type of event it is. Apparently the values on AIX are different
>> from those on Linux, because here's what I see on Linux:
>
> On AIX 5.3 this is:
>
> Python 2.7.1 (r271:86832, Feb 28 2011, 17:51:02)
> [GCC 4.2.4 (Gentoo 4.2.4-r01.2 p1.1)] on aix5
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import select
>>>> dir(select)
> ['PIPE_BUF', 'POLLERR', 'POLLHUP', 'POLLIN', 'POLLMSG', 'POLLNVAL', 'POLLOUT',
> 'POLLPRI', 'POLLRDBAND', 'POLLRDNORM', 'POLLWRBAND', 'POLLWRNORM', '__doc__',
> '__file__', '__name__', '__package__', 'error', 'poll', 'select']
>>>> select.POLLNVAL
> 32768
>>>> select.POLLERR
> 16384

So, apparently POLLERR is the "strange poll event" that's being received.

> On AIX 6.1 it looks similar except for missing 'PIPE_BUF'.
>
>> This will handle the IOError:
>> http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=0a64f784003c11e151405b7f708d77770de0ed57
>
> Yes, that makes it work, thank you!
>
>> It might be risky to skip logging of the POLLNVAL / POLLERR events, so
>> hopefully we can determine their cause and handle them somehow. Do they
>> seem to cause any problems? It might be something specific about pty
>> devices on AIX.
>
> There doesn't seem to go anything wrong so far.

Maybe on AIX, POLLERR is essentially equivalent to POLLHUP in this case.
If that's true, then we could conditionally modify portage's
PollConstants class for AIX like this:

diff --git a/pym/_emerge/PollConstants.py b/pym/_emerge/PollConstants.py
index d0270a9..73a3908 100644
--- a/pym/_emerge/PollConstants.py
+++ b/pym/_emerge/PollConstants.py
@@ -1,6 +1,7 @@
 # Copyright 1999-2009 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2

+import platform
 import select
 class PollConstants(object):

@@ -16,3 +17,8 @@ class PollConstants(object):
 		v *= 2
 	del k, v

+if platform.system() in ('AIX',):
+	# Interpret POLLERR like POLLHUP.
+	PollConstants.POLLHUP = \
+		PollConstants.POLLHUP | PollConstants.POLLERR
+	PollConstants.POLLERR = 0

Does platform.system() return "AIX" exactly as I spelled it?

> I've no idea about programming with pty devices at all.
> However, one relevant (IMHO) thing I can see is:
> portage/util/_pty.py:_can_test_pty_eof() returns True for Linux only.
>
> Anything I can try out?

You can check whether or not pty support is enabled in portage like this:

python -c 'import portage.util._pty, sys;
sys.stdout.write(str(portage.util._pty._disable_openpty))'

-- 
Thanks,
Zac