[perl #55600] regex optimization affected by threads

[John Gardiner Myers (via RT) <perlbug-followup@perl.org>]

# New Ticket Created by  John Gardiner Myers 
# Please include the string:  [perl #55600]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=55600 >



This is a bug report for perl from jgmyers@pong.us.proofpoint.com,
generated with the help of perlbug 1.35 running under perl v5.8.8.


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[Please enter your report here]

The following test program shows a regular expression running quickly
in the main thread, but extremely slowly when run in a thread.  When
run in a thread, it for some reason doesn't follow the find_byclass()
path in the regular expression engine, backtracking like mad.

This reproduces under 5.10.0 as well.

use threads;

sub start_thread {
        split /[.;]+[\'\"]+/, $_[0];
}

my $buffer = '.' x 15000;

if ($ARGV[0]) {
    my $thr = threads->create('start_thread', $buffer);
    $thr->join();
} else {
    start_thread $buffer;
}


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl v5.8.8:

Configured by jgmyers at Tue Feb 13 10:14:49 PST 2007.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=linux, osvers=2.6.9-42.0.8.elsmp, 
archname=i686-linux-thread-multi
    uname='linux pong 2.6.9-42.0.8.elsmp #1 smp tue jan 30 12:33:47 est 
2007 i686 i686 i386 gnulinux '
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define 
usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc-4.1', ccflags ='-D_REENTRANT -D_GNU_SOURCE 
-DTHREADS_HAVE_PIDS -DDEBUGGING -fno-strict-aliasing -pipe 
-Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE 
-D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBUGGING 
-fno-strict-aliasing -pipe -Wdeclaration-after-statement 
-I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.1.1', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', 
lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='gcc-4.1', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.3.4.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.3.4'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:


---
@INC for perl v5.8.8:
    /u/jgmyers/perl/lib/5.8.8/i686-linux-thread-multi
    /u/jgmyers/perl/lib/5.8.8
    /u/jgmyers/perl/lib/site_perl/5.8.8/i686-linux-thread-multi
    /u/jgmyers/perl/lib/site_perl/5.8.8
    /u/jgmyers/perl/lib/site_perl
    .

---
Environment for perl v5.8.8:
    HOME=/u/jgmyers
    LANG=en_US.utf8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    
PATH=/tools/x/bin:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/u/jgmyers/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

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Follow-Ups from:

Dave Mitchell <davem@iabyn.com>

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