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218 lines
7.3 KiB
TeX
218 lines
7.3 KiB
TeX
This document is intended to provide information on how to obtain the
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backtraces required on the asterisk bug tracker, available at
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\url{https://issues.asterisk.org}. The information is required by developers to
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help fix problem with bugs of any kind. Backtraces provide information
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about what was wrong when a program crashed; in our case,
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Asterisk. There are two kind of backtraces (aka 'bt') which are
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useful: bt and bt full.
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First of all, when you start Asterisk, you MUST start it with option
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-g. This tells Asterisk to produce a core file if it crashes.
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If you start Asterisk with the safe\_asterisk script, it automatically
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starts using the option -g.
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If you're not sure if Asterisk is running with the -g option, type the
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following command in your shell:
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\begin{astlisting}
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\begin{verbatim}
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debian:/tmp# ps aux | grep asterisk
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root 17832 0.0 1.2 2348 788 pts/1 S Aug12 0:00 /bin/sh /usr/sbin/safe_asterisk
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root 26686 0.0 2.8 15544 1744 pts/1 S Aug13 0:02 asterisk -vvvg -c
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[...]
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\end{verbatim}
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\end{astlisting}
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The interesting information is located in the last column.
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Second, your copy of Asterisk must have been built without
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optimization or the backtrace will be (nearly) unusable. This can be
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done by selecting the 'DONT\_OPTIMIZE' option in the Compiler Flags
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submenu in the 'make menuselect' tree before building Asterisk.
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After Asterisk crashes, a core file will be "dumped" in your \path{/tmp/}
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directory. To make sure it's really there, you can just type the
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following command in your shell:
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\begin{astlisting}
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\begin{verbatim}
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debian:/tmp# ls -l /tmp/core.*
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-rw------- 1 root root 10592256 Aug 12 19:40 /tmp/core.26252
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-rw------- 1 root root 9924608 Aug 12 20:12 /tmp/core.26340
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-rw------- 1 root root 10862592 Aug 12 20:14 /tmp/core.26374
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-rw------- 1 root root 9105408 Aug 12 20:19 /tmp/core.26426
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-rw------- 1 root root 9441280 Aug 12 20:20 /tmp/core.26462
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-rw------- 1 root root 8331264 Aug 13 00:32 /tmp/core.26647
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debian:/tmp#
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\end{verbatim}
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\end{astlisting}
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In the event that there are multiple core files present (as in the
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above example), it is important to look at the file timestamps in
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order to determine which one you really intend to look at.
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Now that we've verified the core file has been written to disk, the
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final part is to extract 'bt' from the core file. Core files are
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pretty big, don't be scared, it's normal.
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\textbf{NOTE: Don't attach core files on the bug tracker, we only need the bt and bt full.}
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For extraction, we use a really nice tool, called gdb. To verify that
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you have gdb installed on your system:
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\begin{astlisting}
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\begin{verbatim}
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debian:/tmp# gdb -v
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GNU gdb 6.3-debian
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Copyright 2004 Free Software Foundation, Inc.
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GDB is free software, covered by the GNU General Public License, and you are
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welcome to change it and/or distribute copies of it under certain conditions.
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Type "show copying" to see the conditions.
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There is absolutely no warranty for GDB. Type "show warranty" for details.
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This GDB was configured as "i386-linux".
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debian:/tmp#
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\end{verbatim}
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\end{astlisting}
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Which is great, we can continue. If you don't have gdb installed, go install gdb.
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Now load the core file in gdb, as follows:
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\begin{astlisting}
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\begin{verbatim}
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debian:/tmp# gdb asterisk /tmp/core.26252
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[...]
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(You would see a lot of output here.)
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[...]
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Reading symbols from /usr/lib/asterisk/modules/app_externalivr.so...done.
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Loaded symbols for /usr/lib/asterisk/modules/app_externalivr.so
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#0 0x29b45d7e in ?? ()
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(gdb)
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\end{verbatim}
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\end{astlisting}
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Now at the gdb prompt, type: bt
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You would see output similar to:
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\begin{astlisting}
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\begin{verbatim}
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(gdb) bt
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#0 0x29b45d7e in ?? ()
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#1 0x08180bf8 in ?? ()
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#2 0xbcdffa58 in ?? ()
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#3 0x08180bf8 in ?? ()
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#4 0xbcdffa60 in ?? ()
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#5 0x08180bf8 in ?? ()
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#6 0x180bf894 in ?? ()
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#7 0x0bf80008 in ?? ()
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#8 0x180b0818 in ?? ()
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#9 0x08068008 in ast_stopstream (tmp=0x40758d38) at file.c:180
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#10 0x000000a0 in ?? ()
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#11 0x000000a0 in ?? ()
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#12 0x00000000 in ?? ()
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#13 0x407513c3 in confcall_careful_stream (conf=0x8180bf8, filename=0x8181de8 "DAHDI/pseudo-1324221520") at app_meetme.c:262
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#14 0x40751332 in streamconfthread (args=0x8180bf8) at app_meetme.c:1965
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#15 0xbcdffbe0 in ?? ()
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#16 0x40028e51 in pthread_start_thread () from /lib/libpthread.so.0
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#17 0x401ec92a in clone () from /lib/libc.so.6
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(gdb)
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\end{verbatim}
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\end{astlisting}
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The bt's output is the information that we need on the bug tracker.
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\begin{astlisting}
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\begin{verbatim}
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Now do a bt full as follows:
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(gdb) bt full
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#0 0x29b45d7e in ?? ()
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No symbol table info available.
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#1 0x08180bf8 in ?? ()
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No symbol table info available.
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#2 0xbcdffa58 in ?? ()
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No symbol table info available.
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#3 0x08180bf8 in ?? ()
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No symbol table info available.
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#4 0xbcdffa60 in ?? ()
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No symbol table info available.
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#5 0x08180bf8 in ?? ()
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No symbol table info available.
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#6 0x180bf894 in ?? ()
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No symbol table info available.
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#7 0x0bf80008 in ?? ()
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No symbol table info available.
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#8 0x180b0818 in ?? ()
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No symbol table info available.
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#9 0x08068008 in ast_stopstream (tmp=0x40758d38) at file.c:180
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No locals.
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#10 0x000000a0 in ?? ()
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No symbol table info available.
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#11 0x000000a0 in ?? ()
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No symbol table info available.
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#12 0x00000000 in ?? ()
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No symbol table info available.
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#13 0x407513c3 in confcall_careful_stream (conf=0x8180bf8, filename=0x8181de8 "DAHDI/pseudo-1324221520") at app_meetme.c:262
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f = (struct ast_frame *) 0x8180bf8
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trans = (struct ast_trans_pvt *) 0x0
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#14 0x40751332 in streamconfthread (args=0x8180bf8) at app_meetme.c:1965
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No locals.
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#15 0xbcdffbe0 in ?? ()
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No symbol table info available.
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#16 0x40028e51 in pthread_start_thread () from /lib/libpthread.so.0
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No symbol table info available.
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#17 0x401ec92a in clone () from /lib/libc.so.6
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No symbol table info available.
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(gdb)
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\end{verbatim}
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\end{astlisting}
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We also need gdb's output. That output gives more details compared to
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the simple "bt". So we recommend that you use bt full instead of bt.
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But, if you could include both, we appreciate that.
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The final "extraction" would be to know all traces by all
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threads. Even if asterisk runs on the same thread for each call, it
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could have created some new threads.
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To make sure we have the correct information, just do:
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(gdb) thread apply all bt
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\begin{astlisting}
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\begin{verbatim}
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Thread 1 (process 26252):
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#0 0x29b45d7e in ?? ()
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#1 0x08180bf8 in ?? ()
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#2 0xbcdffa58 in ?? ()
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#3 0x08180bf8 in ?? ()
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#4 0xbcdffa60 in ?? ()
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#5 0x08180bf8 in ?? ()
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#6 0x180bf894 in ?? ()
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#7 0x0bf80008 in ?? ()
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#8 0x180b0818 in ?? ()
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#9 0x08068008 in ast_stopstream (tmp=0x40758d38) at file.c:180
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#10 0x000000a0 in ?? ()
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#11 0x000000a0 in ?? ()
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#12 0x00000000 in ?? ()
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#13 0x407513c3 in confcall_careful_stream (conf=0x8180bf8, filename=0x8181de8 "DAHDI/pseudo-1324221520") at app_meetme.c:262
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#14 0x40751332 in streamconfthread (args=0x8180bf8) at app_meetme.c:1965
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#15 0xbcdffbe0 in ?? ()
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#16 0x40028e51 in pthread_start_thread () from /lib/libpthread.so.0
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#17 0x401ec92a in clone () from /lib/libc.so.6
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(gdb)
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\end{verbatim}
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\end{astlisting}
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That output tells us crucial information about each thread.
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Now, just create an output.txt file and dump your "bt full"
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(and/or "bt") ALONG WITH "thread apply all bt" into it.
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Note: Please ATTACH your output, DO NOT paste it as a note.
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And you're ready for upload on the bug tracker.
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If you have questions or comments regarding this documentation, feel
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free to pass by the \#asterisk-bugs channel on irc.freenode.net.
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