From: Kevin Lewis
Date: January 26 2009 11:46pm
Subject: Re: Bug 40633 pushbuild failure: Falcon assertion "lockState == 0"
 failed in SyncObject.cpp
List-Archive: http://lists.mysql.com/falcon/428
Message-Id: <497E4B66.4030301@sun.com>
MIME-Version: 1.0
Content-Type: text/plain; format=flowed; charset=ISO-8859-1
Content-Transfer-Encoding: 7BIT

Olav and Vlad,

It looks to me like cache:flushLock is used to synchronize between 
Cache::flush where syncWait is locked and Cache::ioThread where it is 
unlocked.  Cache::ioThread should never be able to exit with syncWait 
still locked.  But it looks like it can on line 960. if (!flushing)
	if (thread->shutdownInProgress)
		break;

So maybe just as the last ioThread leaves and unlocks flushLock, a 
thread in cache::flush gets flushlock and locks syncWait one last time.

We need a way for Cache::flush to determine, after it gets flushLock, if 
there are any ioThreads to signal.  Should it check 
thread->shutdownInProgress?

Also notice that flushlock is unlocked first.  Should it be the other 
way around?  I think so...

storage\falcon\Cache.cpp(940):		flushLock.unlock();
storage\falcon\Cache.cpp(941):		syncWait.unlock();



Olav Sandstaa wrote:
> Kevin,
> 
> Both Wlad and I have seen that it is the Cache::syncWait sync object 
> that is causing this assert. And I think both of us think that a quick 
> and safe solution is to test if this sync object is locked in the Cache 
> destructor and if so, then just unlock it. Do you agree that that is an 
> OK fix for pushing to the replication branch to make them happy?  To no 
> longer make Falcon code a one of the stoppers for them pushing to 
> mysql-6.0 tree...... If you think this is OK then I will make a patch - 
> and after review push it to the replication branch.
> 
> Still, I think it will be good to understand why this situation happened 
> - and if this is a "bug" in the IO thread, then possibly fix it so that 
> the IO thread is able to do this unlocking of syncWait properly. I have 
> only briefly looked at the Cache::flush() and iothread code so I do not 
> fully understand it yet.
> 
> Olav
> 
>