Re: ps shows same process more than once

[Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>]

On Thu, Nov 28, 2013 at 10:55:04AM -0500, Christopher Faylor wrote:
>On Thu, Nov 28, 2013 at 02:08:13PM +0100, Corinna Vinschen wrote:
>>On Nov 28 15:20, George M. Florendo wrote:
>>> Hi,
>>> 
>>> I run a non cygwin apache process named httpd.exe.  Checking it with
>>> "ps -W" shows a listing of the same process (with PID 4560 in this
>>> case) twice.
>>> 
>>> $ ps -W | grep httpd
>>>      4560    1604    4560       5304  pty0    1000 09:55:21
>>> /home/georgeflorendo/wamp/bin/apache/Apache2.4.4/bin/httpd
>>>      4560    1604    4560       5304  pty0    1000 09:55:21
>>> /home/georgeflorendo/wamp/bin/apache/Apache2.4.4/bin/httpd
>>>      7508       0       0       7508  ?          0 15:09:50
>>> C:\cygwin\home\georgeflorendo\wamp\bin\apache\Apache2.4.4\bin\httpd.exe
>>> 
>>> Doing a "ps aux" shows it only once.
>>> 
>>> $ ps aux
>>>       PID    PPID    PGID     WINPID   TTY     UID    STIME COMMAND
>>>      1340    7856    1340       5720  pty5    1000 15:13:50 /usr/bin/ps
>>>      1604    4008    1604       2292  pty0    1000 09:17:01 /usr/bin/bash
>>>      4008       1    4008       4008  ?       1000 09:17:00 /usr/bin/mintty
>>>      4560    1604    4560       5304  pty0    1000 09:55:21
>>> /home/georgeflorendo/wamp/bin/apache/Apache2.4.4/bin/httpd
>>> 
>>> <snipped>
>>> 
>>> Is it correct that ps -W shows the same process twice?
>>
>>Not exactly but it could happen.  Can you try the latest snapshot Cygwin
>>DLL from http://cygwin.com/snapshots/ and see if it fixes the problem?
>
>I don't see anything in the ChangeLog which would affect this and I'd
>be concerned if there was.
>
>There are scenarios where two different windows pids can be associated
>with the same Cygwin pid.  You should only see it when you do a "ps -W".
>
>So, AFAICT, the correct answer to the "Is it correct" is "Yes'.

Oops.  Sorry.  Just noticed that the pids weren't "different".  There
are still pathological situations where a pid can show up twice when
doing a "ps -W".  I've seen the issue before but fixing it would involve
a global process lock which would slow down Cygwin for the benefit of
a more accurate "ps -W".

cgf

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