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Description

Deletes a semaphore. This function should be used with care as multiple tasks may rely on the presence of the semaphore. Generally speaking, before deleting a semaphore, first delete all the tasks that access the semaphore. As a rule, it is highly recommended to not delete kernel objects at run time.

Deleting the semaphore will not de-allocate the object. In other words, storage for the variable will still remain at the same location unless the semaphore is allocated dynamically from the heap. The dynamic allocation of objects has its own set of problems. Specifically, it is not recommended for embedded systems to allocate (and de-allocate) objects from the heap given the high likelihood of fragmentation.

Files

os.h/os_sem.c

Prototype

OS_OBJ_QTY  OSSemDel (OS_SEM  *p_sem,
                      OS_OPT   opt,
                      OS_ERR  *p_err)

Arguments

p_sem

is a pointer to the semaphore.

...

If OS_CFG_CALLED_FROM_ISR_CHK_EN set to 1 in DEF_ENABLED in os_cfg.h: if attempting to delete the semaphore from an ISR.

OS_ERR_ILLEGAL_DEL_RUN_TIME

If OS_SAFETY_CRITICAL_IEC61508 is defined: you called this after calling OSStart() and thus you are no longer allowed to delete kernel objects.

OS_ERR_OBJ_PTR_NULL

If OS_CFG_ARG_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: if p_sem is a NULL pointer.

...

If OS_CFG_OBJ_TYPE_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: if p_sem is not pointing to a semaphore.

...

If OS_CFG_ARG_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: if one of the two options mentioned in the opt argument is not specified.

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_TASK_WAITING

If one or more tasks are waiting on the semaphore.

Returned Value

NoneThe number of tasks made ready-to-run by this function. Zero either indicates an error or that no tasks were pending on the semaphore.

Required Configuration

OS_CFG_SEM_EN AND and OS_CFG_SEM_DEL_EN must be enabled in os_cfg.h. Refer to uCµC-OS-III Configuration Manual.

Callers

Application.

Notes/Warnings

1. Use this call with care because other tasks might expect the presence of the semaphore.

Example Usage

          OS_SEM  SwSem;
           
           
          void Task (void *p_arg)
          {
              OS_ERR      err;
              OS_OBJ_QTY  qty;
           
           
              (void)&p_arg;
              while (DEF_ON) {
                  :
                  :
                  qty = OSSemDel(&SwSem,
                                  OS_OPT_DEL_ALWAYS,
                                 &err);
                  /* Check "err" */
                  :
                  :
              }
          }