Comtrol eCos - Manual (Page 475)

Chapter 32. µITRON API
The following two functions are supported in this release, when enabled with the configuration option CYG-
PKG_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
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