Re: [Proxool-developer] concurrency bug in Prototyper class?

[Matt S. <msa...@gm...>]

Possibly, but I don't know - it's indeterminate.  Without the proper memory
visibility semantics (e.g. synchronization, immutability, volatile et. al.)
I think all bets are off.


On Fri, Jun 19, 2009 at 1:32 PM, Bill Horsman <bi...@lo...>wrote:

> Is that a problem that corrects itself? In other words, is it a temporary
> problem where a connection is refused when it didn't have to be but that the
> connection count does end up being correct? - Bill
>
> 2009/6/19 Matt Salafia <msa...@gm...>
>
>> It seems Class Prototyper should either acquire the lock on private member
>> 'lock' whenever it reads or modifies 'connectionCount' or make
>> 'connectionCount' a volatile variable.
>>
>> Prototyper.buildConnection( ) acquires the lock to read and modify
>> 'connectionCount' but other methods do not: Prototyper.sweep( ),
>> Prototyper.connectionRemoved( ) and Prototyper.getConnectionCount().
>>
>> I started poking around after my application started seeing
>> ProxoolExceptions indicating the maximum connection count had been reached
>> and discovered what appears to be a memory visibility issue.  If calls to
>> Prototyper.connectionRemoved( ) and Prototyper.buildConnection( ) happen in
>> different threads there could be unwarranted ProxoolExceptions for reaching
>> the maximum connection count - a 'connectionPool' decrement might not be
>> visible to the threads calling Prototyper.buildConnection( ).
>>
>>
>>
>>
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