> De: "Peter Levart" <peter.lev...@gmail.com> > À: "Remi Forax" <fo...@univ-mlv.fr>, "mandy chung" <mandy.ch...@oracle.com> > Cc: "Xueming Shen" <xueming.s...@oracle.com>, "core-libs-dev" > <core-libs-dev@openjdk.java.net> > Envoyé: Vendredi 29 Septembre 2017 22:56:26 > Objet: Re: RFR JDK-8185582, Update Zip implementation to use Cleaner, not > finalizers
> Hi Remi, Hi Peter, > On 09/29/17 22:49, Remi Forax wrote: >> ----- Mail original ----- >>> De: "mandy chung" [ mailto:mandy.ch...@oracle.com | >>> <mandy.ch...@oracle.com> ] >>> À: "Peter Levart" [ mailto:peter.lev...@gmail.com | >>> <peter.lev...@gmail.com> ] >>> , "Xueming Shen" [ mailto:xueming.s...@oracle.com | >>> <xueming.s...@oracle.com> ] >>> , "core-libs-dev" [ mailto:core-libs-dev@openjdk.java.net | >>> <core-libs-dev@openjdk.java.net> ] Envoyé: Vendredi 29 Septembre 2017 >>> 22:34:52 >>> Objet: Re: RFR JDK-8185582, Update Zip implementation to use Cleaner, not >>> finalizers >>> On 9/27/17 2:31 AM, Peter Levart wrote: >>>> Up to a point where 'this' is dereferenced to obtain the 'zsRef' value >>>> (line 261), the Deflater instance is reachable. But after that, even >>>> ensureOpen() may be inlined and 'this' is not needed any more. After >>>> that point, obtaining zsRef.address() and calling setDictionaly on the >>>> obtained address may be racing with Cleaner thread invoking >>>> ZStreamRef.run(): >>> What about making the native setDictionary method as an instance method >>> (currently it's a static method) so that this object remains strongly >>> reachable until the method returns? >> Mandy, >> unlike in C or C++, in Java a reference is garbage collected as soon as you >> do >> not need it anymore, >> so using an instance method will not change the issue here. > I might be wrong, but native instance method is an exception. It can't be > inlined. The preparation for native method invocation makes sure 'this' is > kept > reachable because it can be dereferenced from the native code then and native > code is out-of-bounds for JIT optimization. I do not think that you are wrong now but this is a property (a side effect) of the current implementation, Panama and Metropolis may change that. I think it's better to keep the reference available with a reachability fence. > Regards, Peter Rémi >> one way to be sure that a referenced object is not garbage collected is to >> use [ >> http://docs.oracle.com/javase/9/docs/api/java/lang/ref/Reference.html#reachabilityFence-java.lang.Object >> | >> http://docs.oracle.com/javase/9/docs/api/java/lang/ref/Reference.html#reachabilityFence-java.lang.Object >> ] - >>> Mandy >> Rémi
