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# Task Management Functions

The following functions are fully supported in this release:

    ER sta_tsk(
      ID tskid,
      INT stacd )

    void ext_tsk( void )

    void exd_tsk( void )

    ER dis_dsp( void )

    ER ena_dsp( void )

    ER chg_pri(
      ID tskid,
      PRI tskpri )

    ER rot_rdq(
      PRI tskpri )

    ER get_tid(
      ID *p_tskid )

    ER ref_tsk(
      T_RTSK *pk_rtsk,
      ID tskid )

    ER ter_tsk(
      ID tskid )

    ER rel_wai(
      ID tskid )

The following two functions are supported in this release, when enabled with the configuration option CYGPKG_UITRON_TASKS_CREATE_DELETE with some restrictions:

    ER cre_tsk(
      ID tskid,
      T_CTSK *pk_ctsk )

    ER del_tsk(
      ID tskid )

These functions are restricted as follows:

Because of the static initialization facilities provided for system objects, a task is allocated stack space statically in the configuration. So while tasks can be created and deleted, the same stack space is used for that task (task ID number) each time. Thus the stack size (pk_ctsk->stksz) requested in `cre_tsk()` is checked for being less than that which was statically allocated, and otherwise ignored. This ensures that the new task will have enough stack to run. For this reason `del_tsk()` does not in any sense free the memory that was in use for the task's stack.

The task attributes (pk_ctsk->tskatr) are ignored; current versions of eCos do not need to know whether a task is written in assembler or C/C++ so long as the procedure call standard appropriate to the CPU is followed.

Extended information (pk_ctsk->exinf) is ignored.

## Error checking

For all these calls, an invalid task id (tskid) (less than 1 or greater than the number of configured tasks) only returns E_ID when bad params return errors ( CYGSEM_UITRON_BAD_PARAMS_RETURN_ERRORS is enabled, see above).

Similarly, the following conditions are only checked for, and only return errors if CYGSEM_UITRON_BAD_PARAMS_RETURN_ERRORS is enabled:

- pk_crtk in `cre_tsk()` is a valid pointer, otherwise return E_PAR

- `ter_tsk()` or `rel_wai()` on the calling task returns E_OBJ

- the CPU is not locked already in `dis_dsp()` and `ena_dsp()` ; returns E_CTX

- priority level in `chg_pri()` and `rot_rdq()` is checked for validity, E_PAR

- return value pointer in `get_tid()` and `ref_tsk()` is a valid pointer, or E_PAR

The following conditions are checked for, and return error codes if appropriate, regardless of the setting of CYGSEM_UITRON_BAD_PARAMS_RETURN_ERRORS :

- When create and delete functions `cre_tsk()` and `del_tsk()` are supported, all calls which use a valid task ID number check that the task exists; if not, E_NOEXS is returned

- When supported, `cre_tsk()` : the task must not already exist; otherwise E_OBJ

- When supported, `cre_tsk()` : the requested stack size must not be larger than that statically configured for the task; see the configuration options “Static initializers”, and “Default stack size”. Else E_NOMEM

- When supported, `del_tsk()` : the underlying eCos thread must not be running - this would imply either a bug or some program bypassing the µITRON compatibility layer and manipulating the thread directly. E_OBJ

- `sta_tsk()` : the task must be dormant, else E_OBJ

- `ter_tsk()` : the task must not be dormant, else E_OBJ

- `chg_pri()` : the task must not be dormant, else E_OBJ

- `rel_wai()` : the task must be in WAIT or WAIT-SUSPEND state, else E_OBJ

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