Re: Advice on abort

[Poul-Erik Andreasen <poulerik@pea.dk>]

Dmitry A. Kazakov wrote:
> On Tue, 08 Nov 2005 17:59:41 +0100, Poul-Erik Andreasen wrote:
> 
> 
>>Dmitry A. Kazakov wrote:
> 
> 
>>>It all depends on the particular implementation of the socket library and
>>>how Ada tasks are mapped to system threads and processes. All sorts of
>>>resource leaks are thinkable. For example, you might be unable to listen
>>>that TCP/IP port until process restart or it won't abort etc.
>>
>>The time of the abortion are at the end of the first part of the
>>ACT so a cant se how the following could make any problems.
> 
> 
> Just consider a possible implementation of abort. You have a pending
> operation on some hardware. Let a driver lock TCB and relevant memory pages
> until I/O completion. What an Ada RTL might undertake against that, if
> there is no way to cancel it, or more probably, it just does not know about
> any I/O of this kind?
> 
> Consider Ada RTL scheduling Ada tasks within one system thread. In this
> case any alien I/O will block everything including whole Ada RTL.

Maybee i am a litle dump, but will these to implementation make the same
broblems whether you are inside or outside ACT

> Consider ACT implementation which simply stops busy polling for I/O status
> and leaves things as they are. That is: I/O continues and your task goes
> further. Any consequent operation will block. Any re-opening of the same
> communication channel will fail.

The ACT-feature i made deliberately for dealing with posibbly blocking
situations, and to avoiding a language-feature, on the basis of 
potentiel bad implementation, is to mee a wierd way of thinking.

> --------
> The best solution is to use some semi-standard library. Unfortunately Ada
> does not have sockets. But if we are talking about GNAT then obviously to
> use GNAT.Sockets is the first candidate to consider, because ACT (no pun
> intended (:-)) will hopefully take care of its reasonable implementation of
> all platforms they support.
> 

Quite agree

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