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Re: ps shows same process more than once


On Mon, Dec 02, 2013 at 01:47:09PM +0800, George M. Florendo wrote:
>On 11/29/13, Christopher Faylor wrote:
>> 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".
>
>Oh, I'm sorry too.  Didn't get to read your first sentence earlier.
>I'd rather have a faster cygwin more than a more accurate "ps -W".
>
>Thanks for all your help.

Thanks for understanding.  I will try to revisit this code sometime in
the near future to see if I can do something about this case.  I had a
glimmer of an idea about how to fix this in the thinking room recently.

cgf

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