Re: [gnome-db] Libgda4.0.6 warnings and segfault

[Vivien Malerba <vmalerba gmail com>]

On 5 February 2010 19:11, Alberto Roman Linacero <aroman alienvault com> wrote:
>> > In the specific case of MySQL, if it has been compiled with the
>> > --enable-thread-safe-client option, then the API should be thread safe
>> > and the resulting GdaConnection object (without the
>> > GDA_CONNECTION_OPTIONS_THREAD_SAFE option) should also be thread safe.
>> > So the problem seems to be a bug in Libgda where a lock is acquired
>> > and not released.
>>
>> I guess that MySQL should be compiled with that option, but I'll compile a
>> new one to be sure (we're using tyhe MySQL 5.1 debian package from
>> dotdeb.org)
>
> Well, I've compiled MySQL with the --enable-thread-safe-client but it still
> fails. Also, this message appears in my /var/log/messages:
>
> Feb  5 07:53:11 opensourcesim ossim-server[7987]: MySQL was not compiled with
> the --enable-thread-safe-client flag, only one thread can access the provider
>
> But something should be wrong somewhere, because the binaries has been
> compiled with that flag. To re-check if I was wrong, I took the default mysql
> binaries (wich has that option), but the message still appears.
>

There is obviously something wrong there as the mysql_thread_safe()
function directly returns the status of the
--enable-thread-safe-client flag...

> I started to think that something regarding the gda multithread detection
> could be involved. So I modified the providers/mysql/gda-mysql-provider.c
> file to force the thread use:
>
>  if (!mysql_thread_safe ()) {
> //    provider_class->limiting_thread = g_thread_self ();
>    provider_class->limiting_thread = NULL;
>  }
>  else
>    provider_class->limiting_thread = NULL;
>
> But as you can imagine, I wasn't lucky, the mysql queries fails, and with the
> insertions I get a new error: "MySQL server has gone away" messages (strange,
> because I tested the connection with gda_connection_is_opened() before the
> insertion and it's still alive)

The result is understandable.

Still, I would like to do some more testing in case there is a libgda
bug somewhere. Can you give me an outline on how many MySQL
silmutaneous connections you use, and from how many threads each
connection is used, so I can try to write a test program?

>
> Well, it seems that I'll wait until release 4.2 before continue testing. We're
> going to come back to libgda2.3, because we're going to release a new
> software version very soon and I can't continue the migration. I'll continue
> with the migration and the tests in two weeks or so.
>

Of course in 4.2 this whould work because the new connection option
makes sure only one thread actually uses the MySQL connection object.

Vivien