AoU: ETAS_RTACAR_SM_OS_018
**************************

The ETAS_RTACAR_SM_OS_018 AoU verifies that when extended tasks are used in the RTA-OS configuration,
mandatory stack size configuration parameters are properly defined for any task that can be preempted by an extended task.

Extended tasks in AUTOSAR OS are tasks that can use the ``WaitEvent()`` service to enter a waiting state, 
releasing the processor while waiting for an event to occur. 
Because extended tasks can be preempted and later resumed, they require explicit stack size configuration to ensure sufficient 
memory is allocated for their execution context.

Verification Approach
=====================

The verification is performed by analyzing the OS ECUC configuration files (ARXML) provided via the ``--os-arxml`` parameter or 
discovered in the project directory specified by ``--dir``.

The tool performs the following steps:

1. **Configuration Loading**: Parses the ARXML files to extract the OS configuration, including task definitions and their properties.

2. **Extended Task Detection**: Identifies tasks configured as extended tasks (tasks that reference events via ``OsTaskEventRef``).

3. **Scalability Class Validation**: Checks that the ``OsScalabilityClass`` parameter is consistent across all configuration files. If incompatible values are detected, manual verification is required.

4. **Result Reporting**: Generates one of the following results based on the analysis outcome.


.. important:: Automated Verification Scope

   The current implementation **detects** the presence of extended tasks in the ECUC configuration but does **not yet implement full automated verification** 
   of the stack size configuration constraints specified in the AoU.

When extended tasks are detected, the tool reports a **review** result, requiring manual verification that:

    - Stack size has been specified for **any task that can be preempted by an extended task**.
    - The stack size is sufficient for the task's execution context and any nested preemptions.
   
This manual verification must confirm compliance with the complete AoU requirement as stated in the RTA-CAR Safety Manual.


ARXML Configuration Requirements
================================

To enable this check, the OS ECUC configuration must be provided in AUTOSAR ARXML format. The tool analyzes:

- **Task definitions** (``OsTask`` containers) to identify extended tasks
- **Event references** (``OsTaskEventRef``) to determine which tasks are extended
- **Scalability class settings** (``OsScalabilityClass``) to ensure configuration consistency


.. include:: ../rules/ETAS_RTACAR_SM_OS_018.rst

See Also
========

- :ref:`os_command_options` for information on providing ARXML files via ``--os-arxml`` or ``--dir``
- :cite:t:`ETAS_SM` section on extended task configuration and stack sizing
- :cite:t:`AUTOSAR` specification for extended task scheduling semantics