eCos Reference Manual
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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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