Subject: Re: Pine (imapd?) hangs changing message status

From: Mark Crispin <[email-masked]>
Date: Thu, 4 Jan 1996 17:48:52 -0800

On 4 Jan 1996, Trey Harris wrote:
> If I cd to my ~/mail directory on the IMAP server machine and attempt to
> do anything to read the files in that directory (ls, cat, vi, whatever)
> the command hangs until Pine finishes hanging.  The moment Pine finishes
> hanging, the ls, cat, tail, or whatever abrubtly resumes.

This sounds like an important clue.  If Unix utilities get stuck too, it
suggests that the hanging is happening in the system.

My guess is that fsync() causes some kind of directory lockup.  Pine does
an fsync() on the mail file at certain critical points to ensure that the
disk copy is consistant.  One of those critical points is "all requested
flag updates complete".

Since you are running AIX 4, I suggest nagging IBM to fix their operating
system.  Since we're starting to deploy AIX 4 on our RS/6000s, I suspect
that we'll start encountering this problem too.  It does't happen in AIX
3.

-- Mark --

DoD #0105, R90/6 pilot, FAX: (206) 685-4045  ICBM: N 47 39'35" W 122 18'39"
Science does not emerge from voting, party politics, or public debate.

---

From: [email-masked] (Trey Harris)
Date: 4 Jan 1996 07:51:11 GMT

Recently I've been seeing Pine sometimes hang when I go into a folder
(most often when it's my sent-mail folder), read a few messages and go 
back to my INBOX folder.  All my mail is being accessed via IMAP.

The imapd is the UW imapd included in the distribution of Pine 3.92.  The
client is Pine 3.92.  Both are running on RS/6000 AIX 4 boxes. 

The hang lasts from three to ten minutes.  While the hang is going on,
memstat, iostat, vmstat, monitor, and even netstat all look good on both
machines.  The imapd process (actually rimapd, but I doubt that matters)
does not appear to use any CPU (at least, from a ps listing) for the
duration of the hang.  Usually the hang is with both asterisks visible in
the upper-left corner of the Pine screen, sometimes with neither.  I have
not seen it hang with but a single asterisk. 

The hang only occurs when I have changed the status of a message.  I have
also seen this hang occur immediately upon viewing a message in my
sent-mail folder (which removes the "new" flag).  Usually, however, it 
does not occur until I attempt to close sent-mail and go back to my INBOX.

Has anyone seen this behavior before?  Do you know what to do about it?
-- 
Trey Harris                             http://sunsite.unc.edu/harris/
  System Administrator, Project Isis, Office of Information Technology
                       The University of North Carolina at Chapel Hill