[Info-vax] hung program location

[Stephen Hoffman]

On 2013-02-19 22:21:36 +0000, David Froble said:

> Tom Adams wrote:
> 
>> There is only one AST programmed in. It's a resource wait AST that
>> only fires when the system is telling the process to shutdown, so it
>> did not cause the problem.  None of the QIOs or QIOWs use ASTs.
> 
> If you're using QIO, and don't have a completion AST routine, well, I 
> know nothing, but I've had the impression that a completion AST routine 
> is rather normal to signal the completion of the QIO.

A completion AST routine is common with sys$qio, yes.  It's not 
necessary, though.  You can easily code the routine to continue running 
the mainline code with the I/O outstanding and then — some distance 
forward in the code, when you need to look in the buffer or such — 
issue the equivalent of sys$synch.  A simple double-buffering scheme 
can use a pair of sys$qiow calls and a pair of sys$synch calls in a 
loop, for instance.


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