Hi Sergei I cant, but Heinz has managed to (see https://mariadb.atlassian.net/browse/MDEV-6282) The value of lex at that point is NULL in the core I guess if that situation is impossible by design, this is more likely to be a memory overrun instead... In any case, I got Heinz to try my fix and the crash still happened in the same spot. So I think my next step at this point is valgrind... --A On 02/06/14 20:53, Sergei Golubchik wrote:
Hi, Andrew!
On Jun 02, Andrew McDonnell wrote:
Hi all
(Cross-posted to oqgraph-developers, maria-developers)
I am trying to track down a segfault apparently triggered by concurrent execution of queries through OQGraph - for context, see:
https://mariadb.atlassian.net/browse/MDEV-6282
I am however a bit confused as to what is going on, because at least some of the information leads me to suspect that there could be more going on here than just a simple race condition.
--Immediate Cause--
On the surface, a segfault appears to be caused in a method in sql_class.h, Statement::check_limit_rows_examined() dereferencing a NULL pointer, `lex`. The method check_limit_rows_examined() was called from sql_class.h method handler::increment_statistics() . I don't see how thd->lex could be NULL there. It shouldn't be changed concurrently on anything.
Can you actually repeat the crash?
Regards, Sergei