[Bug 855010] Re: upstart assumes we can stop tracing processes when exec() is called, breaks 'expect daemon' for cups

[Steve Langasek]

I dug into this further and discovered to my surprise that cupsd doesn't
support daemonizing at all, it only supports backgrounding.  And of
course it forks before it calls listen() on its sockets.  So frankly,
I'm not sure how I thought "expect daemon" was going to help here.

Now, even if we patched cupsd to daemonize, or fixed bug #530779,
upstart's handling of the reexec would *still* be a problem.  So I still
think this is a bug in its own right that we should fix.

** Also affects: upstart
   Importance: Undecided
       Status: New

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Title:
  upstart assumes we can stop tracing processes when exec() is called,
  breaks 'expect daemon' for cups

Status in Upstart:
  New
Status in “upstart” package in Ubuntu:
  New

Bug description:
  trying to improve the cups upstart job in Ubuntu to use 'expect
  daemon' so that the service is reliably up before upstart proceeds on
  to running the post-start script, I find that this doesn't work
  because cups re-execs itself with different commandline options before
  daemonizing.  upstart init/job_process.c has the following:

  /*
   [...]
   * We assume that if the job calls exec that it's finished forking so we can
   * drop the trace entirely; we have no interest in tracing the new child.
   **/
  static void
  job_process_trace_exec (Job         *job,
                          ProcessType  process)

  Well, cups obviously violates this expectation, because it unavoidably
  re-execs itself.

  Is the upstart assumption wrong?  Is this sanely *fixable* without
  causing knock-on effects?

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: upstart 1.3-0ubuntu9
  ProcVersionSignature: Ubuntu 3.0.0-11.18-generic 3.0.4
  Uname: Linux 3.0.0-11-generic x86_64
  ApportVersion: 1.23-0ubuntu1
  Architecture: amd64
  Date: Tue Sep 20 11:03:08 2011
  InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
  ProcEnviron:
   PATH=(custom, user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: upstart
  UpgradeStatus: Upgraded to oneiric on 2011-06-27 (85 days ago)

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