AoU: ETAS_RTACAR_SM_OS_221
**************************

This AoU checks that all resources acquired via ``GetResource()`` are released before a task or Category 2 ISR
terminates, according to the ETAS_RTACAR_SM_OS_221 requirement.

The validation procedure simulates a resource stack along all feasible paths leading to task or ISR termination
and verifies that the stack is empty at every termination boundary. Termination boundaries considered include:

- Explicit termination calls: ``TerminateTask()``, ``ChainTask()`` , ``Os_TerminateTask()``, ``Os_ChainTask()`` 
- Implicit return from a task main function
- Return from a Category 2 ISR function

The check is applied only to functions identified as task or Category 2 ISR implementations (i.e., functions matching
the ``TASK`` or ``ISR`` macro patterns).

.. include:: restricted_os_regions_common_rationale.rst

.. important:: Os API call region delimiters

   The tool detects resource acquisition when a call to **Os_GetResource()** (or ``GetResource()``) is made and
   resource release when a corresponding call to **Os_ReleaseResource()** (or ``ReleaseResource()``) is made.

.. attention:: Resource identifier resolution

   The tool does not resolve resource identifiers during analysis. Rules that require matching a specific resource
   identifier are therefore applied without identifier verification. This is a known limitation; the tool reports
   the affected path result as ambiguous when call targets are unresolved.

.. include:: ../rules/ETAS_RTACAR_SM_OS_221.rst