On 08/07/2014 03:43 AM, Jaroslav Tulach wrote:
Dne Čt 7. srpna 2014 08:17:16, Andrew Haley napsal(a):
I'm wondering whether it's really worth your time applying band-aids to
a broken mechanism.
Under the assumption WeakReference and ReferenceQueue are flawless, there is no
reason to call a mechanism based on WeakReference and ReferenceQueue synergy
"broken".
An object can be
"really gone" even when one of its instance methods is still executing.
That would probably signal a major flaw in the JVM.
Finalization is not broken in the sense of not meeting its specs
(see http://docs.oracle.com/javase/specs/jls/se7/html/jls-12.html#jls-12.6)
but some surprising and undesirable cases are allowed,
and actually occur, in highly concurrent programs.
Including cases where finalizers may run concurrently with
the final invocation of a method on the target.
Because the specs interact with the details of the memory model,
we have been discussing (on jmm-dev list) possible changes
and improvements. But in the mean time (or in any case), the best
practice is to consider finalization as a last resort, after
ruling out all other possible cleanup strategies.
Finalization is easy to spec, implement, and control in
purely sequential systems, but is a questionable idea in
concurrent ones.
-Doug
