2.4.29: Zombies not detected or removed

2.4.29: Zombies not detected or removed

[Schwarz]

Hi everyone,

since 2.4.29 we discovered a strange behaviour.

Severall tasks are no longer detected as destroyed.
means, these tasks have ended but arn't removed from
the processlist.

An example from today:

[root@d102 ]# date
Mon Feb 21 10:14:06 CET 2005
[root@d102 ]# strace -p 33326
attach: ptrace(PTRACE_ATTACH, ...): No such process
[root@d102 ]# ps aux | grep 29579
33326    29579  0.0  0.2 10696 4332 ?        SN   10:11   0:00 -f
/home/ajondoco
root     19168  0.0  0.0  1768  628 pts/0    S    10:15   0:00 grep 29579
[root@d102 ]# strace -p 33326
attach: ptrace(PTRACE_ATTACH, ...): No such process
[root@d102 ]#

As you can see the process in question "29579" was started
10:11 , but as finished its activity already. After 10
minutes it's still not removed from the processlist and 
it's not detected as a zombie. 

the task was an Apache 1.3.3 child over a wrapper calling php
with -f option. 

We think it's unimportant if its forked or execev(),because on
another maschine it was not even an apache invoked. 

Some of the these processes enter zombie state, but were never
fully removed !

Any ideas why it and what happens?


mfG. M.Schwarz

Re: 2.4.29: Zombies not detected or removed

[Marcelo Tosatti]

On Mon, Feb 21, 2005 at 12:32:33PM +0100, Schwarz wrote:
> 
> 
> Hi everyone,
> 
> since 2.4.29 we discovered a strange behaviour.
> 
> Severall tasks are no longer detected as destroyed.
> means, these tasks have ended but arn't removed from
> the processlist.
> 
> An example from today:
> 
> [root@d102 ]# date
> Mon Feb 21 10:14:06 CET 2005
> [root@d102 ]# strace -p 33326
> attach: ptrace(PTRACE_ATTACH, ...): No such process
> [root@d102 ]# ps aux | grep 29579
> 33326    29579  0.0  0.2 10696 4332 ?        SN   10:11   0:00 -f
> /home/ajondoco
> root     19168  0.0  0.0  1768  628 pts/0    S    10:15   0:00 grep 29579
> [root@d102 ]# strace -p 33326
> attach: ptrace(PTRACE_ATTACH, ...): No such process
> [root@d102 ]#
> 
> As you can see the process in question "29579" was started
> 10:11 , but as finished its activity already. After 10
> minutes it's still not removed from the processlist and 
> it's not detected as a zombie.  
> 
> the task was an Apache 1.3.3 child over a wrapper calling php
> with -f option. 
> 
> We think it's unimportant if its forked or execev(),because on
> another maschine it was not even an apache invoked. 
> 
> Some of the these processes enter zombie state, but were never
> fully removed !
> 
> Any ideas why it and what happens?

I don't, no. Quite strange.

Can you reproduce this? If sys_ptrace() failed the process is not present. 

Can you please "cat /proc/<pid>/status" when ptrace fails but the ps shows the 
process existance ?

I suppose you haven't been seeing this behaviour with v2.4.28 ?