[PATCH 06/13] config: Add rtems_malloc_task_stack_for_idle()

[Joel Sherrill]

On Tue, Oct 4, 2022 at 12:40 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 30/09/2022 23:39, Chris Johns wrote:
> > On 30/9/2022 7:21 pm, Sebastian Huber wrote:
> >> Update #4524.
> >> ---
> >>   cpukit/doxygen/appl-config.h                | 13 +++++
> >>   cpukit/include/rtems/rtems/config.h         | 29 +++++++++-
> >>   cpukit/include/rtems/score/interr.h         |  1 +
> >>   cpukit/sapi/src/interrtext.c                |  3 +-
> >>   cpukit/sapi/src/malloctaskstackforidle.c    | 59 +++++++++++++++++++++
> >>   spec/build/cpukit/librtemscpu.yml           |  1 +
> >>   spec/build/testsuites/sptests/grp.yml       |  2 +
> >>   spec/build/testsuites/sptests/spfatal36.yml | 19 +++++++
> >>   testsuites/sptests/spfatal36/init.c         | 52 ++++++++++++++++++
> >>   testsuites/sptests/spfatal36/spfatal36.doc  | 11 ++++
> >>   testsuites/sptests/spinternalerror02/init.c |  2 +-
> >>   testsuites/sptests/sptls04/init.c           |  2 +
> >>   12 files changed, 191 insertions(+), 3 deletions(-)
> >>   create mode 100644 cpukit/sapi/src/malloctaskstackforidle.c
> >>   create mode 100644 spec/build/testsuites/sptests/spfatal36.yml
> >>   create mode 100644 testsuites/sptests/spfatal36/init.c
> >>   create mode 100644 testsuites/sptests/spfatal36/spfatal36.doc
> >>
> >> diff --git a/cpukit/doxygen/appl-config.h b/cpukit/doxygen/appl-config.h
> >> index aa6dbae648..ee647dc961 100644
> >> --- a/cpukit/doxygen/appl-config.h
> >> +++ b/cpukit/doxygen/appl-config.h
> >> @@ -4842,6 +4842,19 @@
> >>    * configuration options.  It is assumed that any memory allocated
> for the
> >>    * stack of an IDLE task will not be from the RTEMS Workspace or the
> memory
> >>    * statically allocated by default.
> >> + *
> >> + * For applications with a thread-local storage size which is
> completely
> >> + * unknown at the time the application configuration is defined, RTEMS
> provides
> >> + * an IDLE task stack allocator which uses rtems_malloc().
> >
> > I thought the TLS size was static and set by the linker? Has this
> changed?
>
> No, this didn't change.
>
> >
> > I am confused about the relationship between an unknown TLS size and
> IDLE task?
> > And the relationship of the TLS size and stack size?
>
> Currently, the IDLE task storage area is statically allocated. The size
> of this area is defined by CONFIGURE_IDLE_TASK_STACK_SIZE. So, this
> configuration option doesn't directly specify the IDLE task stack size.
> This size covers also the TLS area.
>

Thanks for speaking up Chris. I also don't like the idea that something that
has said and meant IDLE stack size was getting other items lumped into it.


> >
> >> * * The size of the
> >> + * allocated thread storage area is the sum of stack size defined by
> the
> >> + * #CONFIGURE_IDLE_TASK_STACK_SIZE configuration option and the actual
> >> + * thread-local storage size of the application.
> >
> > The label CONFIGURE_IDLE_TASK_STACK_SIZE provides no insight into it
> being
> > effected by the TLS size.
> >
> >> * * Define this configuration
> >> + * option to ``rtems_malloc_task_stack_for_idle`` to use this
> allocator.  If
> >> + * the memory allocation fails, then the system terminates with the
> >> + * INTERNAL_ERROR_CORE fatal source and the
> >> + * INTERNAL_ERROR_NO_MEMORY_FOR_IDLE_TASK_STACK fatal code during
> system
> >> + * initialization.
> >> + * @endparblock
> >
> > I am confused about the how and why I would use this change?
>
> With the statically allocated storage area for the IDLE task you need at
> least an estimate of the size if you define the application
> configuration. If you can't estimate it, then one option is to simply
> allocate it dynamically.
>
> Maybe a better approach is to allocate the IDLE task storage from the
> workspace by default and use the CONFIGURE_IDLE_TASK_STACK_SIZE really
> for the stack size and not the complete storage area. We could add a new
> configuration option (for example CONFIGURE_IDLE_TASK_STORAGE_SIZE) to
> enable the static allocation.
>


CONFIGURE_IDLE_TASK_STORAGE_SIZE could default to the size of stack size
plus other items but it seems over complicated. Just have IDLE stack size
and the other
area for other items.

I don't know when IDLE task storage size was introduced but it has been a
long
time ago. Changing the semantics of it seems quite wrong.

--joel

>
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