Bug 1600262

Thanks for the report Kyle, it is indeed a bug - the buffer is only 1K. The simplistic patch would just increase that to 8K (or so), but a looping read would be better. Related code should also be audited, which I'll undertake too.

Regards

(In reply to Mark Goodwin from comment #2)
> Thanks for the report Kyle, it is indeed a bug - the buffer is only 1K. The
> simplistic patch would just increase that to 8K (or so), but a looping read
> would be better.

I agree. The looping read doesn't look like the simplest change based on the current implementation, but much more effective than increasing the buffer.

Thanks for picking it up so quickly!

- Kyle Walker

upstream fix posted (still need a QA test). See: 

https://github.com/goodwinos/pcp/commit/73ce19502de10cad6c8a10b2cc7d787bb4717575


commit 73ce19502de10cad6c8a10b2cc7d787bb4717575
Author: Mark Goodwin <mgoodwin>
Date:   Fri Jul 20 16:24:45 2018 +1000

    pmdaproc: rework fetch_proc_pid_stat to use a looping read
    
    RHBZ #1600262 https://bugzilla.redhat.com/show_bug.cgi?id=1600262
    
    fetch_proc_pid_stat() was reading /proc/PID/status with a fixed
    size 1024 byte buffer. This is no longer big enough on most
    machines, causing some metrics to have incorrect values; notably
    the Mems_allowed, Mems_allowed_list, voluntary_ctxt_switches and
    nonvoluntary_ctxt_switches fields were not being read or parsed.
    
    Rework this to use a looping read with a suitably sized malloc'd
    buffer. QA test forthcoming.
    
    modified:   src/pmdas/linux_proc/proc_pid.c

Additional fixes and QA tests for this BZ that will be in pcp-4.1.1

commit a3f27c07ea7f480c16070ada22835375d7c311a0
Author: Mark Goodwin <mgoodwin>
Date:   Sun Jul 29 16:22:52 2018 +1000

    pmdaproc: tweak proc.memory.maps to return empty string for kernel workers
    
    Recent changes broke qa/860 by returning -ENODATA when a process
    has zero length /proc/PID/maps. WHilst this is technically correct,
    it's not historically correct and we need to clear the error and
    instead return a zero length string (as pmdaproc has always done).

commit a5a9195e2c16dd042e547001d67ab47c5b50b3ad
Author: Mark Goodwin <mgoodwin>
Date:   Tue Jul 24 13:41:21 2018 +1000

    pmdaproc: additional proc_pid rework to fix short buffer issues
    
    RHBZ #1600262
    
    Fix short buffer/read issues with some additional proc metrics.
    proc.psinfo.environ (/proc/PID/environ), proc.memory.maps
    (/proc/PID/maps), proc.psinfo.nvctxsw and proc.psinfo.vctxsw
    (/proc/PID/status) and a few others.
    
    modified:   src/pmdas/linux_proc/proc_pid.c

commit 12304c9d71711951b763bbdfd03a4834e0d03114
Author: Mark Goodwin <mgoodwin>
Date:   Sun Jul 29 16:01:03 2018 +1000

    qa: remake qa/1350 to check voluntary_ctxt_switches
    
    nonvoluntary_ctxt_switches in /proc/PID/status can sometimes be zero

commit 0b1fb9c7d8e04173e1036a2186b96393727223e3
Author: Mark Goodwin <mgoodwin>
Date:   Sun Jul 29 12:11:04 2018 +1000

    qa: add test 1350 to test pmdaproc reading /proc/PID/status
    
    RHBZ #1600262 https://bugzilla.redhat.com/show_bug.cgi?id=1600262
    
    new file:   qa/1350
    new file:   qa/1350.out
    modified:   qa/group

pcp-4.1.1-2.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-0baea70d93

pcp-4.1.1-2.fc27 has been submitted as an update to Fedora 27. https://bodhi.fedoraproject.org/updates/FEDORA-2018-bedf3e464f

pcp-4.1.1-2.fc27 has been pushed to the Fedora 27 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-bedf3e464f

pcp-4.1.1-2.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-0baea70d93

Reproduced against pcp-4.1.0-4.el7 and verified against pcp-4.3.0-2.el7.

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, 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-2019:2111