Doubt in importance of SCHEDULER_PRIORITY_APPEND

[Joel Sherrill]

On Wed, Jan 20, 2021 at 1:50 AM Richi Dubey <richidubey at gmail.com> wrote:

> Appending an item to its priority group means adding the item to the end
> of the priority queue of items with the same priority, but when/why do we
> do this? Do all classic tasks have their SCHEDULER_PRIORITY_APPEND_FLAG set
> to 1?
>

There is (was) a specific case in the POSIX implementation that required
the thread to be placed at the head of the list. Hopefully it is still
there or all the Ada conformance tests will not pass. At least, that was
where I encountered code that depended on that very precise behavior.

--joel

>
> On Mon, Jan 18, 2021 at 12:39 PM Sebastian Huber <
> sebastian.huber at embedded-brains.de> wrote:
>
>> On 18/01/2021 07:30, Richi Dubey wrote:
>>
>> > Hi,
>> >
>> > Can someone please explain to me why we add 1 to the priority
>> > in SCHEDULER_PRIORITY_APPEND?
>> >
>> > /**
>> >  * @brief Returns the priority control with the append indicator bit
>> set.
>> >  */
>> > #define SCHEDULER_PRIORITY_APPEND( priority )  \
>> >   ( ( priority ) | SCHEDULER_PRIORITY_APPEND_FLAG )
>> >
>> > What's the reason behind doing this and what do we achieve by this?
>> /**
>>   * @brief Returns true, if the item should be appended to its priority
>> group,
>>   * otherwise returns false and the item should be prepended to its
>> priority
>>   * group.
>>   */
>> #define SCHEDULER_PRIORITY_IS_APPEND( priority ) \
>>    ( ( ( priority ) & SCHEDULER_PRIORITY_APPEND_FLAG ) != 0 )
>>
>> --
>> embedded brains GmbH
>> Herr Sebastian HUBER
>> Dornierstr. 4
>> 82178 Puchheim
>> Germany
>> email: sebastian.huber at embedded-brains.de
>> phone: +49-89-18 94 741 - 16
>> fax:   +49-89-18 94 741 - 08
>>
>> Registergericht: Amtsgericht München
>> Registernummer: HRB 157899
>> Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
>> Unsere Datenschutzerklärung finden Sie hier:
>> https://embedded-brains.de/datenschutzerklaerung/
>>
>> _______________________________________________
> devel mailing list
> devel at rtems.org
> http://lists.rtems.org/mailman/listinfo/devel
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/devel/attachments/20210120/6f6205a3/attachment-0001.html>