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Newsgroups: comp.lang.ada
Date: Wed, 24 Feb 2016 13:37:18 -0800 (PST)
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Subject: Re: Protected Objects and Interrupt Handlers
From: Jere <jere.groups@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:29600
Date: 2016-02-24T13:37:18-08:00
List-Id: <comp.lang.ada>

On Wednesday, February 24, 2016 at 1:29:24 PM UTC-5, Simon Wright wrote:
> GNAT (don't forget there are other Ada compilers!) handles differences
> between tasks & interrupts calling protected procedures very similarly;
> the difference is, I believe, in the way locks are handled.
> 
> I don't know too much about the way AdaCore's bare board implementation
> does this; the way I dealt with this at [1] was to implement
> System.Tasking.Protected_Objects.Lock and .Lock_Read_Only as
> 
>    if in an ISR then
>       null;
>    elsif this PO's ceiling priority is an interrupt priority then
>       --  we are in a task, but this PO deals with interrupts, so we
>       --  mustn't be interrupted
>       disable interrupts;
>    else
>       --  we are in a task and this PO doesn't deal with interrupts
>       take the PO's mutex;
>       raise the priority to the PO's ceiling
>    end if;
> 
> [1] https://sourceforge.net/projects/cortex-gnat-rts/

Ok, that makes more sense then.  Thank you!