kern/72979: unkillable process(es) stuck in `STOP' state

[Mikhail Teterin]

>Number:         72979
>Category:       kern
>Synopsis:       unkillable process(es) stuck in `STOP' state
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Oct 21 21:00:44 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator:     Mikhail Teterin
>Release:        FreeBSD 6.0-CURRENT i386
>Organization:
Virtual Estates, Inc.
>Environment:
System: FreeBSD mi 6.0-CURRENT FreeBSD 6.0-CURRENT #1: Wed Oct 20 12:08:24 EDT 2004 mteterin at mi:/meow/obj/misha/src/sys/Gigabyte i386

	debug.mpsafenet and safevm both set to 0

>Description:

Somehow, it is possible to get a process into a state, where it can not be
killed. The state is reported as `T' by ps and as `STOP' by top. There seems
to be a zomie-child of the process, when this happens:

  UID   PID  PPID CPU PRI NI   VSZ  RSS MWCHAN STAT  TT       TIME COMMAND
 1042  1096     1  57   8  0 68044 50228 -      T     ??    0:27,88 kontact
 1042  4903  1096   0 -84  0     0    0 -      Z     ??    0:03,07 <defunct>

But neither -CONT nor -KILL can get rid of the process. Attempts to ktrace
it result in empty ktrace.out.

>How-To-Repeat:

	It is unclear, what exactly is causing this. So far, I have seen it
	twice -- both time with KDE-programs (KMail and Kontact), which attach
	a debugger to themselves, when crashing (a frequent occurence).

	Whatever mistake KDE may be making in their error-handling, it does
	not explain an unkillable process.

	May be, this has something to do with the threading library (libpthread)?

>Fix:

	Don't know...
>Release-Note:
>Audit-Trail:
>Unformatted: