Re: [xmlvm-users] Implementation of synchronized in objc

[Arno P. <ar...@pu...>]

multiple monitorexit for one monitorenter is certainly a problem and I 
think your approach is a viable solution. Make sure that your 
implementation of lock and unlock are thread safe.

Looking forward to your patch!

Arno


On 12/12/09 1:02 AM, Gergely Kis wrote:
> Hi,
>
> I observed a problem with the way synchronized (or more accurately
> monitorenter and monitorexit) were implemented.
> The use of the @synchronized statement is problematic, because javac
> likes to emit multiple monitorexit's in try / catch branches for a
> single monitorenter in many different cases.
>
> So I took the following approach:
> - added an xmlvmLock and xmlvmUnlock method to the java_lang_Object category
> - these methods simply call [XMLVMLockRegistry lock: self]; and
> [XMLVMLockRegistry unlock: self]; respectively
> - XMLVMLockRegistry is a singleton instance which uses a dictionary to
> store the lock objects for each object which uses the synchronized facility.
> - now the monitorenter and monitorexit implementations are very
> straightforward, basically like this:
>
> _op1.o = _stack[_sp --].o;
> [_op1.o xmlvmLock];
>
> _op1.o = _stack[_sp --].o;
> [_op1.o xmlvmUnlock];
>
> My implementation is currently at a proof of concept level (it leaks
> lock objects currently), but it enabled me to go from ~1100 compile
> errors in the generated code to ~30 in our application.
>
> If you like this approach, I plan to submit this for inclusion after a
> bit more testing (hello world tests were successful).
>
> I also implemented a few missing opcodes in the xsl, but our private
> xmlvm branch is still at r666 of the xmlvm trunk. We will merge from
> trunk soon and then plan to start sending back our changes. We are
> implementing fair chunks of java.io <http://java.io> and java.util (and
> java.lang along the way).
>
> Best Regards,
> Gergely
>
>
> --
> Kis Gergely
> MattaKis Consulting
> Email: ger...@ma... <mailto:ger...@ma...>
> Web: http://www.mattakis.com
> Phone: +36 70 408 1723
>
>
>
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