<AWT Dev> [8] Review request for 7186109: Simplify lock machinery for PostEventQueue & EventQueue

Artem Ananiev artem.ananiev at oracle.com
Mon Sep 10 08:17:18 PDT 2012

On 9/10/2012 6:50 PM, Anthony Petrov wrote:
> On 09/10/12 15:27, Artem Ananiev wrote:
>>> ** This is safe because a thread only ever writes its own value to
>>> flushThread so even if it reads a stale value that value will either be
>>> null or some other thread - either way it is not the current thread so
>>> it proceeds with the main logic.
>> The "flushThread" field is not volatile, so we can't check its value
>> outside of synchronized blocks.
> In this particular case you can do that, and in the above quote David
> explains why.

Got it. I didn't even think about writing the code that survive stale 
values, and therefore missed David's comment. Anyway, I don't think such 
an anti-pattern as reading non-volatile field value outside of 
synchronized block is acceptable. And I'm pretty sure static analyzers 
like FindBugs will find this violation.



> In other words: you only want to check whether the flushThread refers to
> the current thread or not. If it's been actually set by the current
> thread, then this thread must see the correct value w/o any
> synchronization needed. Otherwise, (if it's null or set by another
> thread,) your code will see a value that doesn't refer to the current
> thread, and this is exactly what you wanted to check.
> So I agree with David, this test needs no synchronization.
> --
> best regards,
> Anthony

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