On Monday 02 June 2014 13:23:54 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?
I haven't been able so far to come up with a nice, contained, general test case. However, I can very easily reproduce the crash, on both a CentOS 6 system using MariaDB's rpms as well as on my Slackware systems using a self- compiled version. Grs, Heinz
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