IPC Timeouts

Ronald Aigner ra3 at os.inf.tu-dresden.de
Wed Feb 23 19:49:44 CET 2005

Jonathan S. Shapiro said:
> On Wed, 2005-02-23 at 18:29 +0100, Ronald Aigner wrote:
>> I'm personally convinced that you do not need finite IPC timeouts.
> I believe that this was agreed at the Dresden L4 summit meeting. The
> only well-motivated case for timeouts appears to be interacting with
> physical real-world devices that have embedded timeouts (e.g. disk
> drives -- if the 15ms seek is not complete in 20ms, your drive is dead).
> That is, the "watchdog pattern".
> My memory is that it was agreed that this case is rare enough, and
> occurs in software that is unusual enough, that it is not justified to
> preserve this function in the IPC.
> The remaining cases of "no timeout" and "block indefinitely" should
> remain.
I don't recall that, but then: even better :-)

It was brought to my attention that pagefault timeouts _are_ important as
to enforce trust relation with your communication partner. I don't know
what the semantic of a zero pagefault timeout is. If it means that the
page has to be present and a infinite pagefault timeout means that you
don't care, then finite pagefault timeouts seems reasonable. Still,
defining a useful value seems unpractical to me.

Ronald Aigner
ra3 at os.inf.tu-dresden.de

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