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From: davids@mondo.engin.umich.edu (David Snearline)
Subject: Re: Can I/O Completion routine call 'GetRequest'??
Message-ID: <1991Apr21.224503.12761@engin.umich.edu>
Sender: news@engin.umich.edu (CAEN Netnews)
Organization: Computer Aided Engineering Network (CAEN), University of Michigan
References: <0B010004.nn2ddd@outpost.UUCP>
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Date: Sun, 21 Apr 1991 22:45:03 GMT

In article <0B010004.nn2ddd@outpost.UUCP> peirce@outpost.UUCP writes:
>
>In article <63618@bbn.BBN.COM>, rmitchel@bbn.com (Rob Mitchell) writes:
>> 
>> 
>>     I've created a list of 20 parameter blocks and queued them into a 
>>     pseudo "free" list (at the start of my program).  Each has a "state"
>>     of FREE.  I call ATP's 'GetRequest' asynchronously once using a globally 
>>     created param block (should it really be a global or one of the "free" 
>>     ones?).
>> 
>>     When Mac receives a TReq, my I/O Completion routine assigns reg. A0
>>     (which contains address of current param block) to local variable and
>>     set param's "state" to INCOMING.  
>> 
>>     What I need to do now is queue another 'GetRequest' from my I/O
>>     Completion routine.  Can I call I use a different "free" element
>>     and make the 'GetRequest' call from my I/O Completion routine?
>>     I'm not allocating/moving any memory, right?  GetRequest should
>>     just assign a bunch of pointers, right?  It probably doesn't move
>> 	or allocate any memory, right??
>> 
>>     How else can I have at least one 'GetRequest' always outstanding
>>     at *any* given time?????
>> 
>>     Thanks in advance!!!!
>
>Sounds like you have the right idea.  Calling PGetRequest from a completion
>routine is fine and a common approach found in many programs.  And
>it's the only way to implement programs that live only at interrupt
>level.  Just be doubly sure that that your parameter blocks are really
>free when you reuse them!
>
>Good luck with your project.

Is it possible to re-use the same parameter block from your completion
routine?  ie. Has IODone already called Dequeue on your parameter block
by the time it calls your completion routine?

Thanks in advance.

--
David Snearline
University of Michigan Engineering
davids@mondo.engin.umich.edu