Re: [infinispan-dev] Per-entry lock container

Actually, rather than a ref counter, I could rely on ReentrantLock's hasQueuedThreads(). But even this will not guard against edge cases - threads waiting, and then timing out, preventing the removal of unused locks and presenting a men leak. On 17 Oct 2012, at 07:47, Dan Berindei <dan.berindei(a)gmail.com&gt; wrote: On Wed, Oct 17, 2012 at 3:13 AM, Jason Greene <jgreene(a)redhat.com&gt; wrote: > > > Sent from my iPhone > > On Oct 16, 2012, at 10:39 AM, Jason Greene <jason.greene(a)redhat.com&gt; > wrote: > > >> from _get_ to lock on an eventually created new instance. > > > > Yes if you get the ordering right, it can certainly be done. You might > have to introduce a state-based CAS or secondary lock though for some > scenarios (I haven't thought through them all) I think Manik's point though > was just that getting it right is harder than just making the whole thing > atomic. > > Although there is no way out of the remove, you still have to recheck the > lock is valid after every successful aquire, and then try to lock the new > lock > Right, you still need a retry loop on acquire, so why not use reference counting and actually reuse the lock? I think all you need is a tryAddRef method, something like this: public boolean tryAddRef() { int newCount; int oldCount; do { oldCount = refCount.get(); if (oldCount == 0) return false; newCount = oldCount + 1; } while (!refCount.compareAndSet(oldCount, newCount)); return true; } Then in your acquireLock you call tryAddRef in a loop and when it returns true you can go on and really acquire the lock - knowing that another thread can't remove it from the map. _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev -- Manik Surtani manik(a)jboss.org twitter.com/maniksurtani Platform Architect, JBoss Data Grid http://red.ht/data-grid _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev