[development] sess_write() and PHP processes

[Nic Ivy]

Is sess_write() called by the same PHP process that handles page  
requests?

I'm working with dado to debug node_import.module (see http:// 
drupal.org/node/63581).  node_import.module uses a $_SESSION variable  
to control the workflow state, which is something I've not seen often.

Simply put, the workflow progresses normally for some people (e.g.  
dado) and not for others (e.g. me).  For me, some variables in  
$_SESSION are effectively not updated.  I say "effectively" because  
$_SESSION is written twice.  The second write uses old values.

At one point, I have the following debugging statements:
<?php

watchdog('debug', 'Before');
$_SESSION['node_import'] = $edit; // NOTE: sess_write() calls watchdog 
('debug', 'Writing').
watchdog('debug', 'After');

?>

The logs consistently show, in reverse chronological order:
Writing
After
Before

What's going on?

Nic