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Bug 1843792 - pcp-pmda-lio is crashing
Summary: pcp-pmda-lio is crashing
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: pcp
Version: 8.3
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: 8.4
Assignee: Nathan Scott
QA Contact: Jan Kurik
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-06-04 07:19 UTC by Jan Kurik
Modified: 2021-09-17 12:44 UTC (History)
7 users (show)

Fixed In Version: pcp-5.2.1-2.el8
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-05-18 15:19:32 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
FAF report of the crash (453.46 KB, application/gzip)
2020-06-04 07:19 UTC, Jan Kurik 		no flags Details
View All

Description Jan Kurik 2020-06-04 07:19:39 UTC 
Created attachment 1694982 [details]
FAF report of the crash

Description of problem:
pcp-pmda-lio is crashing when target_core_mod kernel module is not loaded. There are two issues with this:
1) The fact the target_core_mod needs to be explicitly loaded for pcp-pmda-lio to work is not documented anywhere.
2) Even if the target_core_mod kernel module is not loaded, pcp-pmda-lio should not crash. It should shut-down gracefully.

Version-Release number of selected component (if applicable):
I can reproduce this from pcp-pmda-lio-4.3.2-2.el8 to pcp-pmda-lio-5.1.1-1.el8

How reproducible:
Intermittently

Steps to Reproduce:
1. Install pcp-pmda-lio on a fresh RHEL-8.3 release
# yum install -y pcp-pmda-lio pcp-zeroconf
2. Install the PMDA
# cd /var/lib/pcp/pmdas/lio && ./Install
3. Try to get a value from the lio PMDA
# pmval lio.summary.total_luns

Actual results:
# pmval lio.summary.total_luns
pmval: pmGetInDom(142.0): Resource temporarily unavailable

# tail /var/log/pcp/pmcd/lio.log
...
[Thu Jun  4 02:26:18] pmdalio(15276) Error: prefetch: callback failed
[Thu Jun  4 02:30:31] pmdalio(15276) Error: prefetch: callback failed
[Thu Jun  4 02:31:42] pmdalio(15276) Error: preinstance: callback failed

If abrt is enabled then a FAF report is generated (see the attachment).
This is a snip from the backtrace log:

<backtrace>
Traceback (most recent call last):
File "/var/lib/pcp/pmdas/lio/pmdalio.python", line 256, in lio_fetch
self.refresh()
File "/var/lib/pcp/pmdas/lio/pmdalio.python", line 193, in refresh
r = root.RTSRoot()
File "/usr/lib/python3.6/site-packages/rtslib_fb/root.py", line 85, in __init__
modprobe('target_core_mod')
File "/usr/lib/python3.6/site-packages/rtslib_fb/utils.py", line 434, in modprobe
raise RTSLibError("Could not load module: %s" % module)
rtslib_fb.utils.RTSLibError: Could not load module: target_core_mod
</backtrace>

Expected results:
* pcp-pmda-lio handles exceptions from RTS lib
* The need for explicit load of target_core_mod is documented


Additional info:
Comment 1 Nathan Scott 2020-07-06 06:15:11 UTC 
Resolved upstream.  Note I've not made any changes to the
man page, after reviewing it, as I don't think we should
be encouraging manual kernel module loading.  Any modules
needed will be loaded by the iSCSI target initialization
code (not part of PCP) - if they're not loaded then there
are no devices we should be reporting on so the behaviour
(and related doc) is now as it should be I think.

commit 2f48006ecaab3ee4c0c318dc62b24df71659874c (HEAD -> master)
Author: Nathan Scott <nathans>
Date:   Mon Jul 6 16:10:40 2020 +1000

    pmdalio: wrap refresh routine with exception handling
    
    When no iSCSI devices have been created yet the kernel
    modules are not necessarily loaded.  This'll result in
    exceptions from rtslib - so mask these (logged once).
    
    Resolves Red Hat BZ #1843792.
Comment 8 errata-xmlrpc 2021-05-18 15:19:32 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (pcp bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:1754
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