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This queue is for tickets about the Proc-ProcessTable CPAN distribution.

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The Basics
Id: 82175
Status: resolved
Priority: 0/
Queue: Proc-ProcessTable

People
Owner: Nobody in particular
Requestors: Matthew.L.Dailey [...] Dartmouth.EDU
Cc: CARNIL [...] cpan.org
AdminCc:

Bug Information
Severity: (no value)
Broken in: (no value)
Fixed in: (no value)



Subject: Problem with pctcpu on Linux
Date: Sat, 22 Dec 2012 12:29:04 -0500
To: bug-Proc-ProcessTable [...] rt.cpan.org
From: "Matthew L. Dailey" <matthew.l.dailey [...] dartmouth.edu>
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Greetings, We're using Proc::ProcessTable on some beefy linux boxes and found an issue with pctcpu when long-running processes use lots of cpu. On this particular system, there are two six-core cpus with hyperthreading, so there are 24 logical cpus. Under linux, this means there is a theoretical max cpu "percentage" of 2400%. If a process uses lots of cpu for a long time, this causes a buffer overflow in pctcpu once it goes over 999.99%, since it's buffer is only 6 bytes. Here's /proc/<pid>/stat for the process that produces the overflow: # cat /proc/23427/stat 23427 (sdevice) S 16424 23427 16424 34816 23427 4202496 3854777420 3716 11765 0 179490227 1688781 0 0 20 0 44 0 155125884 173169319936 30671991 18446744073709551615 4194304 190125333 140736691917600 140736691909504 47611949540385 0 8192 0 640 18446744073709551615 0 0 17 15 0 0 1540 0 0 And, here's the backtrace if I compile with debugging symbols and run in gdb: #0 0x00007ffff76d5425 in raise () from /lib/x86_64-linux-gnu/libc.so.6 #1 0x00007ffff76d8b8b in abort () from /lib/x86_64-linux-gnu/libc.so.6 #2 0x00007ffff771339e in ?? () from /lib/x86_64-linux-gnu/libc.so.6 #3 0x00007ffff77a9807 in __fortify_fail () from /lib/x86_64-linux-gnu/libc.so.6 #4 0x00007ffff77a8700 in __chk_fail () from /lib/x86_64-linux-gnu/libc.so.6 #5 0x00007ffff77a7b69 in ?? () from /lib/x86_64-linux-gnu/libc.so.6 #6 0x00007ffff76eefcb in __printf_fp () from /lib/x86_64-linux-gnu/libc.so.6 #7 0x00007ffff76ea5b8 in vfprintf () from /lib/x86_64-linux-gnu/libc.so.6 #8 0x00007ffff77a7c04 in __vsprintf_chk () from /lib/x86_64-linux-gnu/libc.so.6 #9 0x00007ffff77a7b4d in __sprintf_chk () from /lib/x86_64-linux-gnu/libc.so.6 #10 0x00007ffff6473297 in sprintf (__s=0x7dc4f8 "1051.1", __fmt=0x7ffff6474f9d "%3.2f") at /usr/include/x86_64-linux-gnu/bits/stdio2.h:34 #11 calc_prec (prs=0x7dc410, format_str=0x7dc510 "iiisiiiillllljjjjijllljjsiiiiiiSSsSS", mem_pool=<optimized out>) at OS.c:542 #12 OS_get_table () at OS.c:651 #13 0x00007ffff6474ab8 in XS_Proc__ProcessTable_table ( my_perl=<optimized out>, cv=<optimized out>) at ProcessTable.xs:353 #14 0x00007ffff7b1384f in Perl_pp_entersub () from /usr/lib/libperl.so.5.14 #15 0x00007ffff7b0ace6 in Perl_runops_standard () from /usr/lib/libperl.so.5.14 #16 0x00007ffff7aac36a in perl_run () from /usr/lib/libperl.so.5.14 #17 0x0000000000400db9 in main () Here is a quick hack to work around this problem: --- Linux.h.orig 2008-09-08 11:08:41.000000000 -0400 +++ Linux.h 2012-12-22 12:04:29.581138706 -0500 @@ -42,7 +42,7 @@ char *cmndline; char *exec; /* other values */ - char pctcpu[sizeof("100.00")]; /* precent cpu, without '%' char */ + char pctcpu[sizeof("1000.00")]; /* precent cpu, without '%' char */ char pctmem[sizeof("100.00")]; /* precent memory, without '%' char */ }; Looking at this, there are also spelling errors in the comments (precent vs. percent), but that's not causing any trouble. :-) --- Linux.c.orig 2008-09-08 11:10:41.000000000 -0400 +++ Linux.c 2012-12-22 12:04:52.121362495 -0500 @@ -539,7 +539,7 @@ float pctcpu = 100.0f * (prs->utime / 1e6) / (time(NULL) - prs->start_time); /* calculate pctcpu - NOTE: This assumes the cpu time is in microsecond units! */ - sprintf(prs->pctcpu, "%3.2f", pctcpu); + sprintf(prs->pctcpu, "%4.2f", pctcpu); field_enable(format_str, F_PCTCPU); /* calculate pctmem */ This is, of course, just a temporary fix, but would make it work with systems with up to 99 cpus. Since this isn't too far off, it might be worth bumping a few more bytes. :-) I hope this helps. Please let me know if you need any more info. Best, Matthew L. Dailey Systems Administrator Thayer School of Engineering Dartmouth College
Subject: Re: [rt.cpan.org #82175] AutoReply: Problem with pctcpu on Linux
Date: Mon, 24 Dec 2012 10:38:18 -0500
To: <bug-Proc-ProcessTable [...] rt.cpan.org>
From: "Matthew L. Dailey" <matthew.l.dailey [...] dartmouth.edu>
Download (untitled) / with headers
text/plain 142b
Just so it's documented here - I've also submitted this as an Ubuntu bug on Launchpad with my patch: <https://bugs.launchpad.net/bugs/1093289>


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