[concurrency-interest] CopyOnWriteArrayNavigableSet review followup

Peter jini at zeus.net.au
Wed Dec 30 20:27:18 EST 2015


An option might be a single threaded executor,  so all writes are uncontended and written by the same thread, then make all access volatile.


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---- Original message ----
From: Dr Heinz M. Kabutz <heinz at javaspecialists.eu>
Sent: 31/12/2015 09:44:54 am
To: Mike Duigou <openjdk at duigou.org>
Cc: Concurrency Interest <concurrency-interest at cs.oswego.edu>
Subject: Re: [concurrency-interest] CopyOnWriteArrayNavigableSet review followup


> 6. Where you use the wrapped COWArrayList for locking, instead of 
> synchronized(super.al.lock) 
> 
> You may be looking at an old implementation of COWArrayList. In the  
> latest JDK9 repo the type of locking has been changed to a standard  
> Java monitor. 
Indeed I was - thank you for that correction. 
>> 10. I am concerned by the number of methods that are being called  
>> whilst holding locks.  Whilst I don't have any concrete example, I am  
>> concerned that this could lead to deadlocks. 
> 
> We only lock on one private object from our own instance so I don't  
> believe there's any risk of deadlock. 
Right, in the version I was looking at you had two - the ReentrantLock  
and the synchronized.  I will still need to check this more carefully,  
considering how long Vector contained a deadlock even with what seemed  
like a single lock :-) 
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