From mboxrd@z Thu Jan  1 00:00:00 1970
Message-Id: <200202261801.NAA07515@math.psu.edu>
To: 9fans@cse.psu.edu
From: Dan Cross <cross@math.psu.edu>
Subject: [9fans] Weird problem.
Date: Tue, 26 Feb 2002 13:01:42 -0500
Topicbox-Message-UUID: 5729c6f4-eaca-11e9-9e20-41e7f4b1d025

I'm looking at a Plan 9 machine where ps(1) keeps hanging; in particular,
it hangs while trying to open one of the status files under /proc/*. (eg,
open("/proc/$somepid/status", OREAD); hangs).  Looking at the source code
to devproc.c, I see that one of the first things procopen() does is lock
p->debug once it finds the proctable entry for the process that particular
file is associated with.  My guess, based only on vague feeling and nothing
more substantial, is that there exists some sort of deadlock with p->debug.

Is there a way to see what locks a process holds, short of instrumenting
the kernel to do so?  I'd hate to simply reboot the machine, since I think
that the error state would be difficult to recreate, and I'd really like
to understand what's going on.  Alternatively, if anyone's seen this before
and knows what's up, that'd be great.

	- Dan C.