Hi, Kristian! On Feb 26, Kristian Nielsen wrote: > I got a crash in my parallel replication test case, and this one turned out to > be caused by a fundamental problem in debug_sync. I am not sure how to solve > it, so I wanted to explain the issue in case others have some ideas. > > The crash happens in THD::awake() when a thread is killed: > > mysql_mutex_lock(&mysys_var->mutex); > ... > int ret= mysql_mutex_trylock(mysys_var->current_mutex); > mysql_cond_broadcast(mysys_var->current_cond); > if (!ret) > mysql_mutex_unlock(mysys_var->current_mutex); > > The problem is that mysys_var->current_mutex changed between the trylock() and > the unlock(), so we unlock a different mutex than the one we locked - ouch!
What about saving mysys_var->current_mutex locally before trylock-ing it? Then you can be sure that you unlock what you've locked. Races are still possible, you can signal a condition that doesn't correspond to the mutex - but it doesn't really matter here. Regards, Sergei _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
