On some operating systems, the error log contains a stack
trace if mysqld dies unexpectedly. You can
use this to find out where (and maybe why)
mysqld died. See
Section 5.2.2, “The Error Log”. To get a stack trace, you must
not compile mysqld with the
-fomit-frame-pointer option to gcc. See
Section 23.5.1.1, “Compiling MySQL for Debugging”.
A stack trace in the error log looks something like this:
mysqld got signal 11; Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x41fd0110 thread_stack 0x40000 mysqld(my_print_stacktrace+0x32)[0x9da402] mysqld(handle_segfault+0x28a)[0x6648e9] /lib/libpthread.so.0[0x7f1a5af000f0] /lib/libc.so.6(strcmp+0x2)[0x7f1a5a10f0f2] mysqld(_Z21check_change_passwordP3THDPKcS2_Pcj+0x7c)[0x7412cb] mysqld(_ZN16set_var_password5checkEP3THD+0xd0)[0x688354] mysqld(_Z17sql_set_variablesP3THDP4ListI12set_var_baseE+0x68)[0x688494] mysqld(_Z21mysql_execute_commandP3THD+0x41a0)[0x67a170] mysqld(_Z11mysql_parseP3THDPKcjPS2_+0x282)[0x67f0ad] mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0xbb7[0x67fdf8] mysqld(_Z10do_commandP3THD+0x24d)[0x6811b6] mysqld(handle_one_connection+0x11c)[0x66e05e]
If resolution of function names for the trace fails, the trace contains less information:
mysqld got signal 11; Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x41fd0110 thread_stack 0x40000 [0x9da402] [0x6648e9] [0x7f1a5af000f0] [0x7f1a5a10f0f2] [0x7412cb] [0x688354] [0x688494] [0x67a170] [0x67f0ad] [0x67fdf8] [0x6811b6] [0x66e05e]
In the latter case, you can use the resolve_stack_dump utility to determine where mysqld died by using the following procedure:
Copy the numbers from the stack trace to a file, for example
mysqld.stack. The numbers should not include the surrounding square brackets:0x9da402 0x6648e9 0x7f1a5af000f0 0x7f1a5a10f0f2 0x7412cb 0x688354 0x688494 0x67a170 0x67f0ad 0x67fdf8 0x6811b6 0x66e05e
Make a symbol file for the mysqld server:
shell>
nm -n libexec/mysqld > /tmp/mysqld.symIf mysqld is not linked statically, use the following command instead:
shell>
nm -D -n libexec/mysqld > /tmp/mysqld.symIf you want to decode C++ symbols, use the
--demangle, if available, to nm. If your version of nm does not have this option, you will need to use the c++filt command after the stack dump has been produced to demangle the C++ names.Execute the following command:
shell>
resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stackIf you were not able to include demangled C++ names in your symbol file, process the resolve_stack_dump output using c++filt:
shell>
resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stack | c++filtThis prints out where mysqld died. If that does not help you find out why mysqld died, you should create a bug report and include the output from the preceding command with the bug report.
However, in most cases it does not help us to have just a stack trace to find the reason for the problem. To be able to locate the bug or provide a workaround, in most cases we need to know the statement that killed mysqld and preferably a test case so that we can repeat the problem! See Section 1.7, “How to Report Bugs or Problems”.