[coyotos-dev] Sleep for interval

[Valerio Bellizzomi]

On 05/10/2007, at 11.56, Christopher Nelson wrote:

>>
>>
>> > A different question might be: should it be possible for the
invocation
>> > to have a timeout? I do not like timeouts in IPC in general, but I am
>> > beginning to suspect that I will eventually be forced (reluctantly)
to
>> > compromise on this issue.
>>
>> If IPC's could have timeouts, then timeouts could easily subsume sleep.
>> Just have a capability that always blocks and do a request on it with a
>> timeout.  You'd nicely have memory where you need it to arrange things
>> kernel side.  Proxying would change, as it wouldn't have any knowledge
>> of this.  Not sure how much of a problem proxying is though.
>>
>
>I am a fan of not having timeouts.  Many of the problems I am confronted
>with in my job involve programmers assuming that "this operation will
>*never* take longer than X time units."  Then it invariably does in a
>situation they didn't anticipate, and the software fails in a really
>unexpected way.

Said in other words this means that using timeouts will make robustness a
harder goal to reach.

>
>On the other hand, there are places where it seems impossible to get away
>from timeouts.  As an example, trying to connect to an unresponsive host.
>You will never get a "fail" message.  At some point you have to stop
>trying.

In places where one can't get away from timeouts, do not use hard-coded
timeouts, use parameters so that they can be adjusted.

>
>With respect to IPC, I don't see a need for timeouts unless it is
possible
>for a receiver to ignore a sender.  If every receiver must response
>positively or negatively to a message, then you don't need timeouts.
>However, if a sender is trying to contact a receiver that is ignoring it,
>at
>some point it either has to give up - or at the very least inform the
user
>somehow that things are taking longer than expected.
>
>-={C}=-
>
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