?? os_task.lst
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C51 COMPILER V7.50 OS_TASK 12/12/2007 16:55:25 PAGE 4
179 1 if (prio > OS_LOWEST_PRIO) { /* Make sure priority is within allowable range */
180 2 return (OS_PRIO_INVALID);
181 2 }
182 1 OS_ENTER_CRITICAL();
183 1 if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority */
184 2 OSTCBPrioTbl[prio] = (OS_TCB *)1; /* Reserve the priority to prevent others from doing ... */
185 2 /* ... the same thing until task is created. */
186 2 OS_EXIT_CRITICAL();
187 2 psp = (void *)OSTaskStkInit(task, ppdata, ptos, 0); /* Initialize the task's stack */
188 2 err = OSTCBInit(prio, psp, (void *)0, 0, 0, (void *)0, 0);
189 2 if (err == OS_NO_ERR) {
190 3 OS_ENTER_CRITICAL();
191 3 OSTaskCtr++; /* Increment the #tasks counter */
192 3 OSTaskCreateHook(OSTCBPrioTbl[prio]); /* Call user defined hook */
193 3 OS_EXIT_CRITICAL();
194 3 if (OSRunning) { /* Find highest priority task if multitasking has started */
195 4 OSSched();
196 4 }
197 3 } else {
198 3 OS_ENTER_CRITICAL();
199 3 OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others */
200 3 OS_EXIT_CRITICAL();
201 3 }
202 2 return (err);
203 2 } else {
204 2 OS_EXIT_CRITICAL();
205 2 return (OS_PRIO_EXIST);
206 2 }
207 1 }
208 #endif
209 /*$PAGE*/
210 /*
211 *********************************************************************************************************
212 * CREATE A TASK (Extended Version)
213 *
214 * Description: This function is used to have uC/OS-II manage the execution of a task. Tasks can either
215 * be created prior to the start of multitasking or by a running task. A task cannot be
216 * created by an ISR. This function is similar to OSTaskCreate() except that it allows
217 * additional information about a task to be specified.
218 *
219 * Arguments : task is a pointer to the task's code
220 *
221 * pdata is a pointer to an optional data area which can be used to pass parameters to
222 * the task when the task first executes. Where the task is concerned it thinks
223 * it was invoked and passed the argument 'pdata' as follows:
224 *
225 * void Task (void *pdata)
226 * {
227 * for (;;) {
228 * Task code;
229 * }
230 * }
231 *
232 * ptos is a pointer to the task's top of stack. If the configuration constant
233 * OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high
234 * memory to low memory). 'pstk' will thus point to the highest (valid) memory
235 * location of the stack. If OS_STK_GROWTH is set to 0, 'pstk' will point to the
236 * lowest memory location of the stack and the stack will grow with increasing
237 * memory locations. 'pstk' MUST point to a valid 'free' data item.
238 *
239 * prio is the task's priority. A unique priority MUST be assigned to each task and the
240 * lower the number, the higher the priority.
C51 COMPILER V7.50 OS_TASK 12/12/2007 16:55:25 PAGE 5
241 *
242 * id is the task's ID (0..65535)
243 *
244 * pbos is a pointer to the task's bottom of stack. If the configuration constant
245 * OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high
246 * memory to low memory). 'pbos' will thus point to the LOWEST (valid) memory
247 * location of the stack. If OS_STK_GROWTH is set to 0, 'pbos' will point to the
248 * HIGHEST memory location of the stack and the stack will grow with increasing
249 * memory locations. 'pbos' MUST point to a valid 'free' data item.
250 *
251 * stk_size is the size of the stack in number of elements. If OS_STK is set to INT8U,
252 * 'stk_size' corresponds to the number of bytes available. If OS_STK is set to
253 * INT16U, 'stk_size' contains the number of 16-bit entries available. Finally, if
254 * OS_STK is set to INT32U, 'stk_size' contains the number of 32-bit entries
255 * available on the stack.
256 *
257 * pext is a pointer to a user supplied memory location which is used as a TCB extension.
258 * For example, this user memory can hold the contents of floating-point registers
259 * during a context switch, the time each task takes to execute, the number of times
260 * the task has been switched-in, etc.
261 *
262 * opt contains additional information (or options) about the behavior of the task. The
263 * LOWER 8-bits are reserved by uC/OS-II while the upper 8 bits can be application
264 * specific. See OS_TASK_OPT_??? in uCOS-II.H.
265 *
266 * Returns : OS_NO_ERR if the function was successful.
267 * OS_PRIO_EXIT if the task priority already exist
268 * (each task MUST have a unique priority).
269 * OS_PRIO_INVALID if the priority you specify is higher that the maximum allowed
270 * (i.e. > OS_LOWEST_PRIO)
271 *********************************************************************************************************
272 */
273 /*$PAGE*/
274 #if OS_TASK_CREATE_EXT_EN
INT8U OSTaskCreateExt (void (*task)(void *pd),
void *ppdata,
OS_STK *ptos,
INT8U prio,
INT16U id,
OS_STK *pbos,
INT32U stk_size,
void *pext,
INT16U opt) reentrant
{
void *psp;
INT8U err;
INT16U i;
OS_STK *pfill;
if (prio > OS_LOWEST_PRIO) { /* Make sure priority is within allowable range */
return (OS_PRIO_INVALID);
}
OS_ENTER_CRITICAL();
if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority */
OSTCBPrioTbl[prio] = (OS_TCB *)1; /* Reserve the priority to prevent others from doing ... */
/* ... the same thing until task is created. */
OS_EXIT_CRITICAL();
if (opt & OS_TASK_OPT_STK_CHK) { /* See if stack checking has been enabled */
if (opt & OS_TASK_OPT_STK_CLR) { /* See if stack needs to be cleared */
pfill = pbos; /* Yes, fill the stack with zeros */
C51 COMPILER V7.50 OS_TASK 12/12/2007 16:55:25 PAGE 6
for (i = 0; i < stk_size; i++) {
#if OS_STK_GROWTH == 1
*pfill++ = (OS_STK)0;
#else
*pfill-- = (OS_STK)0;
#endif
}
}
}
psp = (void *)OSTaskStkInit(task, ppdata, ptos, opt); /* Initialize the task's stack */
err = OSTCBInit(prio, psp, pbos, id, stk_size, pext, opt);
if (err == OS_NO_ERR) {
OS_ENTER_CRITICAL();
OSTaskCtr++; /* Increment the #tasks counter */
OSTaskCreateHook(OSTCBPrioTbl[prio]); /* Call user defined hook */
OS_EXIT_CRITICAL();
if (OSRunning) { /* Find highest priority task if multitasking has started */
OSSched();
}
} else {
OS_ENTER_CRITICAL();
OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others */
OS_EXIT_CRITICAL();
}
return (err);
} else {
OS_EXIT_CRITICAL();
return (OS_PRIO_EXIST);
}
}
#endif
335 /*$PAGE*/
336 /*
337 *********************************************************************************************************
338 * DELETE A TASK
339 *
340 * Description: This function allows you to delete a task. The calling task can delete itself by
341 * its own priority number. The deleted task is returned to the dormant state and can be
342 * re-activated by creating the deleted task again.
343 *
344 * Arguments : prio is the priority of the task to delete. Note that you can explicitely delete
345 * the current task without knowing its priority level by setting 'prio' to
346 * OS_PRIO_SELF.
347 *
348 * Returns : OS_NO_ERR if the call is successful
349 * OS_TASK_DEL_IDLE if you attempted to delete uC/OS-II's idle task
350 * OS_PRIO_INVALID if the priority you specify is higher that the maximum allowed
351 * (i.e. >= OS_LOWEST_PRIO) or, you have not specified OS_PRIO_SELF.
352 * OS_TASK_DEL_ERR if the task you want to delete does not exist
353 * OS_TASK_DEL_ISR if you tried to delete a task from an ISR
354 *
355 * Notes : 1) To reduce interrupt latency, OSTaskDel() 'disables' the task:
356 * a) by making it not ready
357 * b) by removing it from any wait lists
358 * c) by preventing OSTimeTick() from making the task ready to run.
359 * The task can then be 'unlinked' from the miscellaneous structures in uC/OS-II.
360 * 2) The function OSDummy() is called after OS_EXIT_CRITICAL() because, on most processors,
361 * the next instruction following the enable interrupt instruction is ignored. You can
362 * replace OSDummy() with a macro that basically executes a NO OP (i.e. OS_NOP()). The
363 * NO OP macro would avoid the execution time of the function call and return.
364 * 3) An ISR cannot delete a task.
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