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Another thread bomb; save_scalar_at #507

Closed p5pRT closed 20 years ago

p5pRT commented 25 years ago

Migrated from rt.perl.org#1353 (status was 'resolved')

Searchable as RT1353$

p5pRT commented 25 years ago

From rkc@ll.mit.edu

Current directory is /data/esc1/src/parse/ GNU gdb 4.17 Copyright 1998 Free Software Foundation\, Inc. GDB is free software\, covered by the GNU General Public License\, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "sparc-sun-solaris2.6"... (gdb) core core warning​: core file may not match specified executable file. Core was generated by `/usr/local/bin/perl -w ./rtbv.pl'. Program terminated with signal 9\, Killed. Reading symbols from /usr/lib/libsocket.so.1...done. Reading symbols from /usr/lib/libnsl.so.1...done. Reading symbols from /usr/lib/libdl.so.1...done. Reading symbols from /usr/lib/libm.so.1...done. Reading symbols from /usr/lib/libposix4.so.1...done. Reading symbols from /usr/lib/libpthread.so.1...done. Reading symbols from /usr/lib/libc.so.1...done. Reading symbols from /usr/lib/libmp.so.2...done. Reading symbols from /usr/lib/libaio.so.1...done. Reading symbols from /usr/platform/SUNW\,Ultra-30/lib/libc_psr.so.1...done. Reading symbols from /usr/lib/libthread.so.1...done. Reading symbols from /usr/local/lib/perl5/site_perl/5.005/sun4-solaris-thread/auto/DBI/DBI.so...done.

Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/attrs/attrs.so...done.

Reading symbols from /usr/local/lib/perl5/site_perl/5.005/sun4-solaris-thread/auto/DBD/mysql/mysql.so...done.

Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/Thread/Thread.so...done.

Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/IO/IO.so...done. Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/Fcntl/Fcntl.so...done.

Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/Socket/Socket.so...done.

Reading symbols from /usr/local/lib/perl5/5.00503/sun4-solaris-thread/auto/IPC/SysV/SysV.so...done.

Reading symbols from /usr/lib/nss_files.so.1...done. #0 0x7c7d8 in save_scalar_at () (gdb) where #0 0x7c7d8 in save_scalar_at () #1 0x7c990 in Perl_save_scalar () #2 0x5cd48 in Perl_pp_gvsv () #3 0x9cadc in Perl_runops_standard () #4 0x21b94 in perl_call_sv () #5 0xef4721d0 in threadstart () (gdb) quit

Debugger finished

Site configuration information for perl 5.00503​:

Configured by rkc at Fri Jun 11 14​:28​:51 EDT 1999.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration​:   Platform​:   osname=solaris\, osvers=2.6\, archname=sun4-solaris-thread   uname='sunos bruno 5.6 generic_105181-03 sun4u sparc sunw\,ultra-30 '   hint=recommended\, useposix=true\, d_sigaction=define   usethreads=define useperlio=undef d_sfio=undef   Compiler​:   cc='gcc'\, optimize='-O'\, gccversion=2.8.1   cppflags='-D_REENTRANT -I/usr/local/include -I/opt/local/include -I/opt/gnu/include'   ccflags ='-D_REENTRANT -I/usr/local/include -I/opt/local/include -I/opt/gnu/include'   stdchar='unsigned char'\, d_stdstdio=define\, usevfork=false   intsize=4\, longsize=4\, ptrsize=4\, doublesize=8   d_longlong=define\, longlongsize=8\, d_longdbl=define\, longdblsize=16   alignbytes=8\, usemymalloc=y\, prototype=define   Linker and Libraries​:   ld='gcc'\, ldflags =' -L/usr/local/lib -L/opt/local/lib -L/opt/gnu/lib'   libpth=/usr/local/lib /opt/local/lib /opt/gnu/lib /lib /usr/lib /usr/ccs/lib   libs=-lsocket -lnsl -ldb -ldl -lm -lposix4 -lpthread -lc -lcrypt   libc=/lib/libc.so\, so=so\, useshrplib=false\, libperl=libperl.a   Dynamic Linking​:   dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags=' '   cccdlflags='-fPIC'\, lddlflags='-G -L/usr/local/lib -L/opt/local/lib -L/opt/gnu/lib'

Locally applied patches​:  

@​INC for perl 5.00503​:   /usr/local/lib/perl5/5.00503/sun4-solaris-thread   /usr/local/lib/perl5/5.00503   /usr/local/lib/perl5/site_perl/5.005/sun4-solaris-thread   /usr/local/lib/perl5/site_perl/5.005   .

Environment for perl 5.00503​:   HOME=/export/home/rkc   LANG=C   LANGUAGE (unset)   LD_LIBRARY_PATH=/opt/SUNWspro/lib​:/usr/openwin/lib​:/usr/local/lib   LOGDIR (unset)  
PATH=/opt/local/bin​:/usr/local/jdk1.1.2/bin​:/opt/SUNWspro/bin​:/export/home/rkc​:/opt/local/tcpdump​:/data/se4/mcclung/audit_tools​:/data/se4/mcclung/tcpdumpfiles/scripts​:/usr/openwin/bin/xview​:/usr/openwin/bin​:/1/security/bin​:/bin​:/usr/local/bin​:/usr/ucb​:/usr/bin​:/usr/etc​:/data/se0/gnu/bin​:/opt/local/SunOS4/bin​:/opt/local/bin​:/data/se0/rpl/lnknet/bin​:/data/se0/rpl/stat/bin​:/usr/ccs/bin​:/opt/local/SunOS4/bin​:/export/home/rkc/bin​:/.sim/bin​:/usr/local/mysql/bin  
PERL_BADLANG (unset)   SHELL=/bin/tcsh

-- Dr. Robert K. Cunningham Information System Technology Group   rkc@​ll.mit.edu MIT Lincoln Laboratory
*** My comments\, my opinions​: my responsibility. PGP key available from http​://pgpkeys.mit.edu​:11371

p5pRT commented 25 years ago

From [Unknown Contact. See original ticket]

On Thu\, 9 Sep 1999\, Rob Cunningham wrote​:

This is a bug report for perl from rkc@​ll.mit.edu generated with the help of perlbug 1.26 running under perl 5.00503.

-----------------------------------------------------------------

[GDB trace snipped]

While I don't want to downplay the usefulness of a GDB calltrace (or whatever it's named)\, it's really not enough information to identify a bug. Could you perhaps send the (hopefully short) piece perl code that triggered this program death? (Keeping in mind that accessing any perl variable from two threads simultaneously\, without using the lock() primitive to coordinate access\, has the potential to kill the perl interpreter at some\, possibly random\, point)

  Dan

p5pRT commented 25 years ago

From [Unknown Contact. See original ticket]

Alas\, the code is for an application that is > 10\,000 lines long\, and the bug only appears after more than ten minutes of processing many megabytes of data. I tried to cut the code down\, but couldn't get the bug to re-occur\, thus my less-than-completely useful report. Would it be useful if I re-compile perl with -g and give you the exact line it died on\, or would this not really help much?

BTW\, I have seen perl spawn more than 130 threads executing this application\, happily co-existing and running. (Thanks for your perl thread regexp workaround.)

As for your concern about multi-threaded access of a global variable\, I do not believe that I access any unlocked global variable from multiple threads\, other than to read global configuration variables set up before threads are spawned.

Rob

Dan Sugalski wrote​:

On Thu\, 9 Sep 1999\, Rob Cunningham wrote​:

This is a bug report for perl from rkc@​ll.mit.edu generated with the help of perlbug 1.26 running under perl 5.00503.

-----------------------------------------------------------------

[GDB trace snipped]

While I don't want to downplay the usefulness of a GDB calltrace (or whatever it's named)\, it's really not enough information to identify a bug. Could you perhaps send the (hopefully short) piece perl code that triggered this program death? (Keeping in mind that accessing any perl variable from two threads simultaneously\, without using the lock() primitive to coordinate access\, has the potential to kill the perl interpreter at some\, possibly random\, point)

                                    Dan

-- Dr. Robert K. Cunningham Information System Technology Group   rkc@​ll.mit.edu MIT Lincoln Laboratory
*** My comments\, my opinions​: my responsibility. PGP key available from http​://pgpkeys.mit.edu​:11371

p5pRT commented 25 years ago

From [Unknown Contact. See original ticket]

On Thu\, 9 Sep 1999\, Rob Cunningham wrote​:

Alas\, the code is for an application that is > 10\,000 lines long\, and the bug only appears after more than ten minutes of processing many megabytes of data. I tried to cut the code down\, but couldn't get the bug to re-occur\, thus my less-than-completely useful report. Would it be useful if I re-compile perl with -g and give you the exact line it died on\, or would this not really help much?

Not much\, unfortunately. There's unlikely to be enough info available.

BTW\, I have seen perl spawn more than 130 threads executing this application\, happily co-existing and running. (Thanks for your perl thread regexp workaround.)

Cool!

As for your concern about multi-threaded access of a global variable\, I do not believe that I access any unlocked global variable from multiple threads\, other than to read global configuration variables set up before threads are spawned.

It's remotely possible that the global reads are causing the problem\, but not that likely. (Read access in perl code can update the underlying data structures if they need to be promoted. Printing a scalar variable that was an integer stringifies it and caches the stringified value\, for example\, which can cause problems) It's also possible that something went wrong early in the program but the corruption was only noticed later.

Debugging threaded code is\, unfortunately\, an amazing pain at times. :(

  Dan