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From: craigr@netcom.com (Craig Robertson)
Newsgroups: comp.unix.internals,comp.unix.wizards,comp.unix.bsd
Subject: SunOS 4.1.1 debuggee hangs at PRI=-5 during ptrace attach
Date: 17 May 1994 23:15:54 -0400
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Greetings. 

I'm occasionally having a problem attaching dbx to a reasonably large
process that has been stopped (via SIGSTOP) and swapped out.  Occasionally,
dbx will not be able to attach to this process (the ptrace attach call will
hang) and "ps -axlww" will show the process at PRI=-5 (from a previous?
biowait) with a WCHAN of 0...

I suspect a race in the special-condition of "if the debuggee is already
stopped and you're attempting an attach" in ptrace().  I'm curious if this
is Sun-specific code or if it exists in regular BSD unix...

Machines on which I see this are:
  Both sun4c and sun4 architectures
  Have at least 32MB of physical memory
  Have *plenty* of swap space

I am a SunOS source licensee but this stuff seems *really* tricky... 

I have a service call logged with Sun, but time is really of the essense
on this issue.  Any pointers or help would be appreciated.

Thanks in advance,
Craig Robertson
craigr@netcom.com
-- 
Craig Robertson
craigr@netcom.com