I don't think you can clone() a hashmap in a threadsafe way without
locking it. Of course you could sync{ clone() }, which is faster than
sync{ walk map, check for conflicts }.
Which maybe what Dain was suggesting in the first place.
-David
On Sat, 12 Jan 2002, Bill Burke wrote:
> Good thought. Doesn't this make things really slow? Maybe a clone isn't so
>expensive.
> ----- Original Message -----
> From: Dain Sundstrom
> To: 'Bill Burke' ; [EMAIL PROTECTED]
> Sent: Saturday, January 12, 2002 4:12 PM
> Subject: RE: [JBoss-dev] need help with deadlock detection
>
>
> A thought on the performance issue.
>
> You could copy the hash map, and then do the detection. If you detect a deadlock,
>then synchronize the entire map and run it again. This way you only force a lock on
>the whole map when you really think there is a deadlock.
>
> -dain
> -----Original Message-----
> From: Bill Burke [mailto:[EMAIL PROTECTED]]
> Sent: Saturday, January 12, 2002 2:33 PM
> To: [EMAIL PROTECTED]
> Subject: [JBoss-dev] need help with deadlock detection
>
>
> Can somebody look at server/src/.../ejb/plugins/lock/BeanLockSupport.java and
>QueuedPessimisticEJBLock.java for me? I added an application deadlock detection
>algorithm and need another set of eyeballs to make sure that I didn't do anything too
>drastic. Don't worry, the code is very simple.
>
> Here are my concerns:
>
> - could I detect phantom deadlocks?
> - A static HashMap is used to store tx's that are waiting on other tx's. I
>synchronize on this object whenver I do a deadlock detection. This may be a
>performance hit because every thread that needs to detect for deadlock(it is waiting
>on a tx) will need to synch on it. I thought it may be ok since the algorithm should
>be pretty quick.
>
> All and all this detection algorithm should greatly help out with debugging and
>improve throughput of applications that have application deadlock(they won't wait for
>a tx timeout, instead, the rollback will happen immediately). I really need your
>concerns, comments and questions.
>
>
> Thanks,
>
> Bill
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