OSTaskResume

Description

Resumes a task suspended through the OSTaskSuspend() function. In fact, OSTaskResume() is the only function that can unsuspend a suspended task. Obviously, the suspended task can only be resumed by another task. If the suspended task is also waiting on another kernel object such as an event flag, semaphore, mutex, message queue etc., the suspension will simply be lifted (i.e., removed), but the task will continue waiting for the object.

The user can “nest” suspension of a task by calling OSTaskSuspend() and therefore must call OSTaskResume() an equivalent number of times to resume such a task. In other words, if suspending a task five times, it is necessary to unsuspend the same task five times to remove the suspension of the task.

Files

os.h/os_task.c

Prototype

void  OSTaskResume (OS_TCB  *p_tcb,
                    OS_ERR  *p_err)

Arguments

p_tcb

is a pointer to the TCB of the task that is resuming. A NULL pointer is not a valid value as one cannot resume the calling task because, by definition, the calling task is running and is not suspended.

p_err

is a pointer to a variable that will contain an error code returned by this function.

OS_ERR_NONE

If the call was successful and the desired task is resumed.

OS_ERR_OS_NOT_RUNNING

If OS_CFG_INVALID_OS_CALLS_CHK_EN is set to DEF_ENABLED in os_cfg.h: if µC/OS-III is not running yet.

OS_ERR_STATE_INVALID

If the task is in an invalid state.

OS_ERR_TASK_NOT_SUSPENDED

If the task attempting to be resumed is not suspended.

OS_ERR_TASK_RESUME_ISR

If OS_CFG_CALLED_FROM_ISR_CHK_EN set to DEF_ENABLED in os_cfg.h: if calling this function from an ISR.

OS_ERR_TASK_RESUME_SELF

If OS_CFG_ARG_CHK_EN is set to DEF_ENABLED in os_cfg.h: if passing a NULL pointer for p_tcb or, a pointer to the current TCB. It is not possible to resume the calling task since, if suspended, it cannot be executing.

Returned Value

None

Required Configuration

OS_CFG_TASK_SUSPEND_EN must be enabled in os_cfg.h. Refer to µC-OS-III Configuration Manual.

Callers

Application.

Notes/Warnings

None

Example Usage

          OS_TCB   TaskY;
           
           
          void TaskX (void *p_arg)
          {
              OS_ERR err;
           
           
              while (DEF_ON) {
                  :
                  :
                  OSTaskResume(&TaskY,
                               &err);            /* Resume suspended task        */
                  /* Check "err" */
                  :
                  :
              }
          }