Re: [9] RFR(S): 8005873: JRuby test_respond_to.rb asserts with: MT-unsafe modification of inline cache

[Remi Forax]

On 05/16/2014 05:22 PM, Paul Sandoz wrote:

On May 16, 2014, at 5:05 PM, Remi Forax <fo...@univ-mlv.fr> wrote:

On 05/16/2014 01:56 PM, Tobias Hartmann wrote:

Hi,

thanks to everyone for the feedback.

Is it sufficient then to use synchronized (lambdaForms) { ... } in 
setCachedLambdaForm(..) and a normal read in cachedLambdaForm(..)?

Thanks,
Tobias

no, it's not,
The memory model doesn't guarantee that a normal read will see that another 
thread has changed the array item,
the normal read may always see null.

You need a synchronized block around the normal read.

I don't think that is required since the pattern is:

   form = cachedLambdaForm(which);
   if (form != null) return form
   ...
   form = /new form/
   ...
   form = setCachedLambdaForm(which, form);
   return form;

and the setCachedLambdaForm will, within it's the synchronized block, first 
perform a read to check if there is already a non-default value present.

Paul.

Ok, got it,
it should work :)

cheers,
Rémi