maria-developers team mailing list archive

[Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx>]

Vladimir Kolesnikov <vladimir@xxxxxxxxxxxxx> writes:

> Unfortunately I cannot repeat the problem on my machine. Can you
> please put the branch to the debian box that you gave earlier access
> to?

Yes.

There is now a build directory on the box:

    /home/buildbot/shutdown-crash/mysql-5.1.41-MariaDB-beta/

(I pushed the corresponding bzr version to
lp:~knielsen/maria/maria-pbxt-shutdown-crash. This is a merge of PBXT into
MariaDB).

I built using

    BUILD/compile-pentium-max

I get the test failure repeatably with this:

    (cd mysql-test && perl mysql-test-run.pl mysqld_option_err)

It does not seem to fail the same way every time, but it does seem to fail
everytime I run it.

Let me know if you need anything else.

Thanks again for looking into this!

 - Kristian.

> Kristian Nielsen wrote:
>> [I Cc'ed Paul, let me know if there is another prefered way of communicating,
>> like using Launchpad bugs or some mailing list]
>>
>> Vladimir Kolesnikov <vladimir@xxxxxxxxxxxxx> writes:
>>
>>   
>>> "Crash during shutdown (need help from PBXT team)"
>>>
>>> can you provide any details?
>>>     
>>
>> Yes, of course! Just been busy with other stuff, but very happy that you
>> mention it on your own initiative!
>>
>> Basically, after merging PBXT I see crashes in the main.mysqld_option_err test
>> case. Here is an example build from Buildbot showing this:
>>
>>     http://askmonty.org/buildbot/builders/debian5-i386-fulltest/builds/52
>>     http://askmonty.org/buildbot/builders/debian5-i386-fulltest/builds/52/steps/test_4/logs/stdio
>>
>> The failure appears to be somewhat random, but I was able to repeat it easily
>> enough locally using a release build. Debug build did not seem to show the
>> problem.
>>
>> The issue is with the fix that Paul pushed for Bug#489088:
>>
>>     https://bugs.launchpad.net/pbxt/+bug/489088
>>
>> === modified file 'storage/pbxt/src/myxt_xt.cc'
>> --- storage/pbxt/src/myxt_xt.cc	2009-11-27 15:37:02 +0000
>> +++ storage/pbxt/src/myxt_xt.cc	2009-12-01 09:50:46 +0000
>> @@ -3041,6 +3041,14 @@ xtPublic MX_CHARSET_INFO *myxt_getcharse
>>  	return (MX_CHARSET_INFO *)&my_charset_utf8_general_ci;
>>  }
>>  +#ifdef DBUG_OFF
>> +//typedef struct st_plugin_int *plugin_ref;
>> +#define REF_MYSQL_PLUGIN(x)		(x)
>> +#else
>> +//typedef struct st_plugin_int **plugin_ref;
>> +#define REF_MYSQL_PLUGIN(x)		(*(x))
>> +#endif
>> +
>>  xtPublic void *myxt_create_thread()
>>  {
>>  #ifdef DRIZZLED
>>
>> +	LEX_STRING& plugin_name = REF_MYSQL_PLUGIN(new_thd->variables.table_plugin)->name;
>> +	if ((plugin_name.length == 4) && (strncmp(plugin_name.str, "PBXT", plugin_name.length) == 0)) {
>> +		REF_MYSQL_PLUGIN(new_thd->variables.table_plugin)->ref_count--;
>> +	}
>>  	new_thd->thread_stack = (char *) &new_thd;
>>  	new_thd->store_globals();
>>  	lex_start(new_thd);
>>
>> This code crashes because new_thd->variables.table_plugin is NULL at this
>> point in the code (or at least sometimes is).
>>
>> So this problem is similar to the previous problem handled just above in the
>> code with global_system_variables.table_plugin being NULL.
>>
>> I tried a patch like this:
>>
>> === modified file 'storage/pbxt/src/myxt_xt.cc'
>> --- storage/pbxt/src/myxt_xt.cc	2009-12-01 09:50:46 +0000
>> +++ storage/pbxt/src/myxt_xt.cc	2009-12-04 21:41:25 +0000
>> @@ -3112,10 +3112,15 @@ xtPublic void *myxt_create_thread()
>>  	 * references to the PBXT plugin object and will effectively
>> deadlock the plugin so  	 * that server will have to force
>> plugin shutdown. To avoid deadlocking and forced shutdown  	 * we
>> must dereference the plugin after creating THD objects.
>> +	 * Similarly to global_system_variables.table_plugin as described above,
>> +	 * new_thd->valriables.table_plugin can also become NULL due to shutdown.
>>  	 */
>> -	LEX_STRING& plugin_name = REF_MYSQL_PLUGIN(new_thd->variables.table_plugin)->name;
>> -	if ((plugin_name.length == 4) && (strncmp(plugin_name.str, "PBXT", plugin_name.length) == 0)) {
>> -		REF_MYSQL_PLUGIN(new_thd->variables.table_plugin)->ref_count--;
>> +	plugin_ref table_plugin = new_thd->variables.table_plugin;
>> +	if (table_plugin) {
>> +		LEX_STRING& plugin_name = REF_MYSQL_PLUGIN(table_plugin)->name;
>> +		if ((plugin_name.length == 4) && (strncmp(plugin_name.str, "PBXT", plugin_name.length) == 0)) {
>> +			REF_MYSQL_PLUGIN(table_plugin)->ref_count--;
>> +		}
>>  	}
>>  	new_thd->thread_stack = (char *) &new_thd;
>>  	new_thd->store_globals();
>>
>> So this fixes the crashes, but of course re-introduces the original problem in
>> Bug#489088 with warnings about forced shutdown.
>>
>> I think you should be able to repeat the problem easily enough on Linux with a
>> non-debug build running the test main.mysqld_option_err, but if not let me
>> know and I will help set something up.
>>
>>  - Kristian.
>>   
>
>
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