OS_TLS_GetValue

Description

Returns the current value of a task’s TLS (thread-local storage) stored in the task’s p_tcb->TLS_Tbl[id]. See Chapter 20, “Thread Safety of the Compiler’s Run-Time Library” for details on TLS.

Files

os.h/os_tls.c

Prototype

OS_TLS  OS_TLS_GetValue (OS_TCB    *p_tcb,
                         OS_TLS_ID  id,
                         OS_ERR    *p_err);

Arguments

p_tcb

is a pointer to the OS_TCB of the task you wish to retrieve the TLS from. You will get a copy of the p_tcb->TLS_Tbl[id] entry and of course, the entry will not be changed.

id

is the TLS ID of the entry you desire.

p_err

is a pointer to a variable that contains an error code returned by this function. Possible values are:

OS_ERR_NONE

If the call was successful and the caller was returned the value.

OS_ERR_OS_NOT_RUNNING

If you called OS_TLS_GetValue() and the kernel has not started yet. However, it’s acceptable to call this function prior to starting multitasking but in this case, you must specify a non-NULL pointer for p_tcb.

OS_ERR_TLS_ID_INVALID

If you called OS_TLS_GetValue() and specified a TLS ID that has not been assigned. See OS_TLS_GetID() about assigning TLS IDs.

OS_ERR_TLS_NOT_EN

If you called OS_TLS_GetValue() but the task was created with the option OS_OPT_TASK_NO_TLS indicating that the task does not need TLS support.

Returned Value

The value store in p_tcb->TLS_Tbl[id] or NULL if an error occurred.

Required Configuration

OS_CFG_TLS_TBL_SIZE must be greater than 0 in os_cfg.h. Refer to µC-OS-III Configuration Manual.

Callers

Application.

Notes/Warnings

You cannot call OS_TLS_GetValue() for a task until that task gets created.

Example Usage

OS_TLS_GetValue() example usage

          OS_TLS_ID   MyTLS_ID;
           
           
          void MyTask (void *p_arg)
          {
              OS_ERR      err;
              OS_TLS      p_tls;
           
           
              :
              :
              while (DEF_TRUE) {
                  p_tls = OS_TLS_GetValue((OS_TCB   *)0,
                                         (OS_TLS_ID)MyTLS_ID,
                                         (OS_ERR  *)&err);
                  /* Check "err" */
                  :
                  :
              }
          }