[PATCH 6/7] score: Always validate ticks in _TOD_Validate()

[Sebastian Huber]

On 04/09/2021 06:20, Joel Sherrill wrote:
> 
> 
> On Fri, Sep 3, 2021, 11:01 PM Chris Johns <chrisj at rtems.org 
> <mailto:chrisj at rtems.org>> wrote:
> 
>     On 3/9/21 11:33 pm, Sebastian Huber wrote:
>      > The behaviour with respect to the handling of the ticks member in
>     the *_when()
>      > directives was inconsistent.  In all *_when() directives the
>     ticks member is
>      > not used to calculate the watchdog expiration time.  However, the
>      > rtems_task_wake_when() directive ignores the ticks member of the
>     time of day
>      > completely, unlike the rtems_timer_fire_when() and
>      > rtems_timer_server_fire_when() directives which check that the
>     ticks are valid
>      > and then ignore them.
>      >
>      > This commit changes _TOD_Validate() to unconditionally check the
>     ticks value.
>      > Ignoring the value would make it more difficult to support the
>     ticks in the
>      > future.  The watchdog implementation supports a nanoseconds
>     resolution.
>      > Checking the ticks in rtems_task_wake_when() may case problems
>     for existing
>      > applications which could now get an error status due to an
>     invalid ticks value.
>      >
>      > Applications should set the ticks value to zero for future
>     compatibility.  This
>      > recommendation needs to be added to the documentation.
> 
>     What happens with existing applications that do not touch this value?
> 
> 
> Randomly different behaviour.

Yes, if a user only partially initializes the time of day structure, 
then the application may observe sporadic errors.

> 
> Before all _when operations occurred on seconds boundaries.  This will 
> implicitly change that or return an error.
> 
> I'm not opposed to the improved granularity but hope it doesn't burn too 
> many users.
> 

My approach would be to check the ticks member in RTEMS 6.1 in all 
*_when() directives and support it in RTEMS 7.1.

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