threads/136345: Recursive read rwlocks in thread A cause deadlock with write lock in thread B

Nick Esborn nick at
Thu Jul 16 17:56:58 UTC 2009

On Jul 16, 2009, at 10:53 AM, Attilio Rao wrote:

> 2009/7/16 Nick Esborn <nick at>:
>> KDB, DDB, SCHED_ULE, and PREEMPTION are already turned on.  I will  
>> try
>> when I
>> first upgraded to 8.0, this server was unable to handle its  
>> workload with
>> the INVARIANTS and WITNESS options turned on.
> What do you mean with 'unable'? What was happening precisely?

System time would rise during periods of peak demand, and the system  
would quickly fall behind on its workload of queries.

However, I have some hardware I can dedicate to this, and only run the  
one MySQL data set which exhibits this problem.  That should be enough  
of a workload reduction to allow the server to keep up even with all  
the above options turned on.


>> Also, it can take a while for it to become clear that the deadlock  
>> has
>> occurred -- usually our monitoring picks it up when replication falls
>> behind.  So it may be 15-20 minutes after the deadlock that I am  
>> able to run
>> the above db commands.  Of course the thread will still be  
>> deadlocked.
>> Hopefully that doesn't reduce the value of the data obtained.
> It should be still fine.
> Thanks,
> Attilio
> -- 
> Peace can only be achieved by understanding - A. Einstein

nick at - all messages cryptographically signed

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