[infinispan-dev] deadlock detection on local caches

[Manik Surtani]

On 8 Jul 2009, at 20:16, Mircea Markus wrote:

> Hi,
>
> Original design[1] treats the situation in which two replicating  
> transaction are in a deadlock.
> Here is an idea for a similar mechanism intended for detecting  
> deadlocks on a local cache.
>
> T1, T2 two transactions running on the same local cache.
> T1 has lock on k1 and tries to acquire k2
> T2 has lock on k2 and tries to acquire k1
>
> Each thread runs the following algorithm, (similar to one described  
> in [1])
>
> lock(int timeout)
> {
>  while (currentTime < startTime + timeout)
>  {
>     if (acquire(smallTimeout)) break;
>     testEDD(globalTransaction, key);
>  }
> }
>
>
>
> //will run the same algorithm, by both T1 and T2:
> //globalTransaction - this is the tx that couldn't acquire lock in  
> 'smallTimeout'
> //key - the key that couldn't be locked by globalTransation
>
> testEDD(globalTransaction, key)
> globalTransaction.setLockIntention(key); //we intend to lock the  
> given key...
> Object lockOwner = getLockOwner(key);
> if (isLocallyOriginatedTx(lockOwner)) {
>  Object keyToBeLocked = lockOwner.getLockIntention();   if  
> (globalTransaction.ownsLock(keyToBeLocked)) {

surely you mean lockManager.ownsLock(globalTransaction, key).

But yes, this would be handy to break deadlocks on local transactions.

> 	//this is a deadlock situation
> 	//use coin toss to determine which tx should rollback!!!
> 	return;
>  } else {
> 	return; //this will go back to the main loop in 'lock(int timeout)'  
> method
>  }
> }
>
> Cheers,
> Mircea
>
>
> [1] http://tinyurl.com/nunmyu
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--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org