Re: [infinispan-dev] Doubts about TxDistributionInterceptor and possible break in transaction isolation
On Mon, Jun 17, 2013 at 7:00 PM, Mircea Markus <mmarkus(a)redhat.com> wrote:
On 17 Jun 2013, at 16:11, Dan Berindei <dan.berindei(a)gmail.com> wrote:
> > I think that, given that the local node is not owner, the lock
acquisition is redundant even for pessimistic caches.
> > Mind creating a test to check if dropping that lock acquisition
doesn't break things?
>
> I created a JIRA with low priority since it does not affect the
> transaction outcome/isolation and I believe the performance impact
> should be lower (you can increase the priority if you want).
>
> https://issues.jboss.org/browse/ISPN-3237
>
> If we don't lock the L1 entry, I think something like this could happen:
There is a lock happening *without* L1 enabled.
Nope, tx1 doesn't lock k1 on B because it doesn't do a put(k1, v3) - it
only reads the value from B. So even if tx2 does lock k1 on B, it doesn't
add any synchronization between tx1 and tx2.
But tx1 does write the entry to L1 on A, so it should acquire an "L1 lock"
on A - and tx2 should also acquire the same lock.
>
> tx1@A: remote get(k1) from B - stores k1=v1 in invocation context
> tx2@A: write(k1, v2)
> tx2@A: commit - writes k1=v2 in L1
> tx1@A: commit - overwrites k1=v1 in L1
>
>
Cheers,
--
Mircea Markus
Infinispan lead (www.infinispan.org)
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