[Nagiosplug-devel] [ nagiosplug-Bugs-1250191 ] ECHILD in waitpid (popen.c:spclose)

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Bugs item #1250191, was opened at 2005-08-02 13:39
Message generated for change (Comment added) made by tonvoon
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Category: General plugin execution
Group: Release (specify)
Status: Open
Resolution: None
Priority: 5
Submitted By: Peter Pramberger (peterpramb)
>Assigned to: Ton Voon (tonvoon)
Summary: ECHILD in waitpid (popen.c:spclose)

Initial Comment:
After installing Nagios 2.0b3 and plugins 1.4/1.4.1 on
a CentOS 4.1 machine (a RedHat ES 4.1 clone,
kernel-2.6.9, glibc-2.3.4) I found that the check_dns
plugin always aborts with "DNS WARNING - nslookup
returned error status" except in the first run.

However running it in verbose mode always shows a
successful nslookup output. After some debugging I
found that the waitpid call in popen.c:spclose()
returns a ECHILD, which triggers a failure return value
to be passed back to check_dns. 

Cacthing the ECHILD always produces a reasonable
output, so the child with nslookup is really working.

>From the (linux) manpage: ECHILD if the process
specified in pid does not exist or is not a child of
the calling process. (This can happen for one's own
child if the action for SIGCHLD is set to SIG_IGN. See
also the LINUX NOTES section about threads.)

Shouldn't waitpid be successful in reading the exit
status of the child? Maybe a bug in glibc?

Anyone else seen this?


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>Comment By: Ton Voon (tonvoon)
Date: 2005-09-05 17:27

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Agreed with Sean to take over this call.

Have created a testcase. Sascha Runschke is raising this to Red Hat.

New patch from Peter Pramberger attached.

Depending on reply from Red Hat, will apply patch next week.

Ton

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Comment By: M. Sean Finney (seanius)
Date: 2005-09-02 12:03

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ECHLD is returned in this context when the child has already
exited, and shouldn't be treated as an error.  i'll commit a
change to cvs shortly.

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