Philippe Bernadat (p.bernadat@opengroup.org)
Fri, 19 Mar 1999 08:55:28 +0100
About separate namespaces and heaps > > Regarding the stopping of threads. > > We do not believe that a general solution that allows thread X to stop > thread Y is necessary. It might be desirable, but it might also be impossible > because of the problems involved in writing async-signal-safe code, but > it's probably not necessary. > > Instead, we argue to introduce a process model: a given activity, such > as a servlet, applet, or mobile agent, is encapsulated in a "process". > Processes can be asynchronously killed by destroying (a la Thread.destroy) > their threads. > > Processes are isolated from each other by giving them separate namespace, > separate heaps, and separate CPU and network allocation. Shared state is > kept in a "kernel", separated from user processes by a "red line" --- very > much akin to the traditional user/kernel mode boundary. > We have adopted something similar for the conversant project at the Open Group RI mid summer 98. We felt the real challenge was how to deal with the shared objects (amongst which system classes). The conversant project was about active networks and protection against denial of service. We did implement a prototype (on kaffe, with ANTS) where the creation of a new namespace led to the creation of what we called a private heap. We did address the sharing of system objects via a system heap, but we did not address the sharing of non system state/data between different namespaces (i.e. routing table, caches). One way is to copy the objects, the other is to mediate the access/creation of shared spaces through explicit interfaces. But the issue of sharing state/data in uncooperative environments is somewhat more general and orthogonal to JAVA anyway. If anyone is interested you can still access the conversant homepage at http://www.camb.opengroup.org/RI/PubProjPgs/CONVERSANT.htm and I have made the code available as well as our latest publication at http://www.gr.opengroup.org/~bernadat/conversant Unfortunately the project has been canceled last fall when the Cambridge OpenGroup RI was downsized. Philippe ---------------------------------------------------------------------------- To unsubscribe (or other requests) mailto:majordomo@media.mit.edu List archives, FAQ, member list, etc. http://gee.cs.oswego.edu/dl/javares/
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