On Mon, Dec 02, 2002 at 11:01:32PM +1000, Stephen Crawley wrote: > In theory, the fix is simple; perform all blocking syscalls from within > GC points. In practice, Kissme uses the Classpath native libraries for > Java I/O. Therefore, we must: > > EITHER implement our own native I/O libraries, > > OR make some Kissme-specific changes to the Classpath sourcecode base.
This is not true. You simply need considers all JNI calls as GC points. In other words, as soon as a thread enters native code, it is considered GC safe, as no reference can be directly touched by that thread (all references being hidden within native global/local reference black structures). The important thing is to block such native thread if it ever calls back the JVM (through the JNIEnv function pointers) while GC is running. > I've explored the latter approach and found that it can be done in a > way that should be invisible[*] to other VMs that use the Classpath native > libraries. Here is how this works: Even though these changes would be invisible to other VMs, I think it would be bad design for Kissme. Have you considered what would happen if a "user supplied" JNI library contained a blocking call, or some kind of infinite loop without call-backs into the Kissme JVM? Such a library would deadlock the Kissme JVM if GC was required on another thread. Unless, of course, you had the intention to require users to make Kissme-specific calls around such things, which defeats the purpose of a "Standard native interface" (JNI). SableVM uses a single atomic operation (Compare-And-Swap) around JNI calls to manage thread GC state without causing the overhead of a full mutex lock call. I could explain to you the algorithm. I am currently putting the *final* post-defense/evaluation touch to my Ph.D. thesis document (I have just successfully defended it last week). If I have time, I might add an appendix that describes the implemented stop-the-world algorithm. Etienne -- Etienne M. Gagnon http://www.info.uqam.ca/~egagnon/ SableVM: http://www.sablevm.org/ SableCC: http://www.sablecc.org/ _______________________________________________ Classpath mailing list [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/classpath
