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Re: DProf bug report: infinite loop at startup

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Slaven Rezic
April 16, 2003 12:11
Re: DProf bug report: infinite loop at startup
Message ID: (Mark Brader) writes:

> I'm reporting a problem expereinced with DProf.  The documentation I have
> says to email the perl5-porters list, so that's what I'm doing -- I hope
> it's still the right destination, as this is necessarily a somewhat verbose
> bug report.
> On my work computer (not the one I'm sending this message from), I'm running
> Red Hat Linux 7.2 with, I believe, kernel 2.4.18-5.  And I have "perl, v5.8.0
> built for i686-linux-thread-multi" installed.
> Yesterday I was in a directory containing two files:
> $ ls -l
> total 852
> -r--r--r--    1 msb      msb        408583 Apr  9 13:32 G.pdf.xil
> -r--r--r--    1 msb      msb        451166 Apr  9 13:31
> and I typed this command into a shell (bash pretending to be sh):
> $ for i in *.xil
> .. do
> .. j=`basename $i .xil`                  
> .. time perl -d:DProf `which` $i
> .. mv tmon.out tmon.out.$j
> .. time dprofpp -u -O 50 tmon.out.$j >top50.$j
> .. done; ls -lS; lpr top50*
> and then left for the day.
> (The above is moused directly from the screen, except that I have replaced
> my $PS1 and $PS2, which are made of colored spaces, with $ and ... for the
> sake of readability.)
> The above should have taken about 4 hours to complete.  When I got back
> the next day, it was still running.
> The first perl invocation should have expanded to:
>     time perl -d:DProf /home/xxxx/xxx/xxxx/xxxx/bin/ G.pdf.xil
> (where I have x'd out part of the pathname for security reasons), and by
> running "ps" in another window, I confirmed that it had.  This process
> should have taken about 20 minutes to run; it had now been running for
> more than 20 CPU-hours....
> According to "top", the process was using only a little over 4 megabytes
> of memory.  See for yourself (moused from the window where I ran it):
> 30172 msb       25   0  4160 4160  1328 R    99.8  0.8  1224m perl
> Here is the critical thing: a tmon.out file had been created, but the
> file was only 9 lines long and not growing!  The file contained:
> |   #fOrTyTwO
> |   $hz=100;
> |   $XS_VERSION='DProf 20000000.00_01';
> |   # All values are given in HZ
> |   $over_utime=4; $over_stime=0; $over_rtime=4;
> |   $over_tests=10000;
> |                                                                                                                                                                                                                                                   
> |   
> |   PART2
> (I have prefixed each line with "|    " for readability.)
> Also, the program had not produced any of the output files that it
> normally would if not being debugged, similarly suggesting that it
> had never really gotten started.
> I tried sending the perl process various signals and nothing seemed to
> happen.  (The program uses "confess" and I was hoping for a traceback.)
> A co-worker than suggested connecting to it with strace, but this gave
> a segmentation fault.
> I now killed the perl process (using signal 9) and the for-loop that
> I had typed the day before then iterated and started the program
> on the second input file, as it should have.  This ran correctly and took
> the expected time.  I then moved the output files to a safe place (using
> another window) and then typed !! (in the original window) to repeat the
> for-loop.
> This time the program started up as expected, producing the expected
> tmon.out file correspoding to input file G.pdf.xil.
> I haven't used DProf very much, but have never seen perl exhibit this
> sort of behavior when I was not running DProf.  I concluded that there
> is some sort of random behavior, such as a race condition, that can
> affect DPRof in my environemnt and cause it to go into an infinite
> loop at startup.  I presume it is a relatively rare problem or else it
> would have been fixed already, but I have no idea how rare it might be,
> since I haven't used DProf very much.
> I know this isn't much to go on.  If anyone wants to suggest something
> to try by way of further diagnosis if it happens again, I will try it.
> On the other hand, if this is a known bug, and especially if it has
> been fixed already, it would be good to hear about a patch.

Can you try the same with perl-5.8.1-to-be? As far as I know, there
were some serious performance problems using the -d switch with
perl-5.8.0, which should be solved now.


Slaven Rezic -

    tknotes - A knotes clone, written in Perl/Tk.

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