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

Vladimir Ivanov vladimir.x.ivanov at oracle.com
Wed May 28 10:48:38 UTC 2014

Looks good.

It should be safe to sync on MTF instance since it's not accessible 
outside (MTF and MT.form() are package-private).

Best regards,
Vladimir Ivanov

On 5/28/14 1:49 PM, Tobias Hartmann wrote:
> Hi,
> thanks everyone for the feedback!
> @Remi: I agree with Paul. This is not a problem because if the normal
> read sees an outdated null value, a new LambdaForm is created and
> setCachedLambdaForm(...) is executed. This will guarantee that the
> non-null value is seen and used. The unnecessary creation of a new
> LamdaForm is not a problem either.
> @John: I added the code that you suggested to simulate CAS. Please find
> the new webrev at:
> http://cr.openjdk.java.net/~anoll/8005873/webrev.02/
> Sorry for the delay, I was on vacation.
> Thanks,
> Tobias
> On 19.05.2014 20:31, John Rose wrote:
>> On May 16, 2014, at 4:56 AM, Tobias Hartmann
>> <tobias.hartmann at oracle.com> wrote:
>>> Is it sufficient then to use synchronized (lambdaForms) { ... } in
>>> setCachedLambdaForm(..) and a normal read in cachedLambdaForm(..)?
>> Yes, that is how I see it.  The fast path is a racy non-volatile read
>> of a safely-published structure.
>> (If safe publication via arrays were broken, java.lang.String would be
>> broken.  But the JMM is carefully designed to support safe publication
>> of array elements, and through array elements.)
>> — John

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