Re: JavaMemoryModel: PC language alert: catatonia action

From: Vijay Saraswat (
Date: Sun May 16 2004 - 08:06:38 EDT

    We need to have a name for an action where a thread spins in an
    infinite loop without every issuing any interthread actions (e.g.,
    while (true); ). Since normally, only actions we consider are
    actions that interact with other threads, it doesn't issue any of
    the actions we normally use.

    Right now, we are using the term catatonia action, and say that a
    thread may perform an infinite sequence of
    catatonia actions.

    I just wanted to see if anyone had a suggestion for a better name,
    or thought we should avoid catatonia since it refers to a real
    sickness/disability some people have.


Jeremy Manson wrote:

>>I do think that both "catatonia" and "reclusive" sound rather unpleasant.
>>I may be missing something, but isn't the term "silent action" or "tau
>>action" commonly used for this? See e.g. the literature on the pi-calculus.
>I believe that "silent actions" and "tau actions", like SKIP in CSP, don't
>do anything. A catatonia action requires that the thread perform nothing
>but catatonia actions thereafter.
This concept is very well understood and is called divergence. A silent
action is an *action*. It does something, namely allow the process to
progress internally, in a way that is not observable by the environment.
A process that engages in an infinite set of such actions, thereby not
giving the environment any opportunity to influence its behavior, is
said to be divergent.

For the authoritative definition of this term, one prolly has to go back
to Hoare/CSP or Milner/CCS or Matthew Hennessey/Milner for testing
equivalences in the late 80s -- way before the pi-calculus.


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