Getting locks and sharing: was RE: Getting concurrency

Alex Arnon <>
Tue Jun 21 16:59:50 CEST 2005


On 6/21/05, Ulf Wiger (AL/EAB) <> wrote:

[snip]
> 
> I think the idea of discarding messages might be a way forward,
> but think that one must go further than to just randomly
> discard them. It is very useful to know for sure that if
> s1 and s2 have been sent from P1 to P2, then if s2 arrives,
> s1 is guaranteed to have arrived before it. The spec doesn't
> state this, but it's what I think it should state.
> 
> That would mean that if you start discarding messages to
> a process, you had better continue to discard them, until
> the program somehow takes action (an appropriate action
> might be to restart the process whose mailbox has been
> effectively disabled.)
> 
> /Uffe
> 

Would there be a reason to prefer random discard? I.e., if we rephrase 
    ...if s2 arrives then s1 is guaranteed to have arrived before it...
 to 
    ...if s2 arrives then s1 is guaranteed to have either arrived
before it or never arrived.

This would then simulate a congested network, which might be a more
"generic" way of handling memory-full situations.



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