Re: Protected Objects and Interrupt Handlers

[Simon Wright <simon@pushface.org>]

Dennis Lee Bieber <wlfraed@ix.netcom.com> writes:

> On Thu, 25 Feb 2016 15:59:46 +0000, Simon Wright <simon@pushface.org>
> declaimed the following:
>
>>Maciej Sobczak <see.my.homepage@gmail.com> writes:
>>
>>> Note also that it is easy to combine these two approaches - just let
>>> the interrupt handler (a procedure) interact with a dedicated
>>> protected object (by forwarding to its procedures) as if it was a
>>> regular work-item producing task - which, conceptually, it really is.
>>
>>I think this approach might have problems; if the PO doesn't expect to
>>be called in an interrupt context, it may do things (like block) which
>>an ISR should never do.
>>
> 	As I recall, Ada protected objects are not supposed to contain anything
> that could block.
>
> http://www.iuma.ulpgc.es/users/jmiranda/gnat-rts/node25.htm#SECTION00814000000000000000

That's for code _inside_ the PO. As the document you reference says,

   In general, code executed inside a protected object should be as
   brief as possible. This is because whilst the code is being executed
   other tasks are delayed when they try to gain access to the protected
   object.

and you wouldn't want an ISR to be "delayed when [it tries] to gain
access to the protected object".