Her dissertation is a good explanation on how a Java program may be adapted into having support for thread suspension and resume. She based her work on a complete code re-writing (both at source and byte-code level), following a (theoretically correct) set of transformations. In short, a program must emulate the creation of a continuation on each code sentence, using an exception mechanism to capture the state of the running program. This exception usage is handy, because after catching an exception the code may throw it again, or store (persistently) the execution state. Obviously there's the problem of non serializable resources having to be saved and restored, and the local, temporary variables. Tao, cleverly leaves this issue to the application creator, with two resolution strategies:
- Creating a wrapper class to the resource, that knows how to close and recreate it (e.g., close a file port and re-opening it a few days later);
- Setting the an existing object field to the resource placed in a local variable;
The process is heavily focused on the Java Virtual Machine, and the transformation is not proved to make such sense in other programming languages/environments. Nevertheless, the byte-code transformation strategy is well documented and several performance considerations are made throughout the dissertation. I, however, believe that this approach may be simplified - particularly the exception-based technique used to save/restore execution state - when the application is written in some other languages, like Scheme, that natively support first-class continuations.
Her motivation to this technique is well founded, focusing both portability (she may employ this transformations on several applications, and even with other programming languages, as long as their core is closely related to Java's) and code mobility (inevitably the best reason to save thread execution state and to be able to restore/resume it later, although "Moving long running applications from desktops to laptops and back also has clear appeal").
One interesting point she states from the beginning of the report is that making a thread persistently saved is quite similar to having it migrated to another place, the difference being that the store is the run-time environment of another process/machine.
If you're interested in execution-flow migration, thread state, and similar issues, I advise you to read this report, or at least to skim through it.