What is the purpose of the parameter "struct softirq_action *a" being
passed into tasklet_action() since it doesn't appear to be used
anywhere in the function?
How does the list in __get_cpu_var(tasklet_vec).list get populated?
It looks like at the top of the tasklet_action() call the list is set
to empty and at the bottom __get_cpu_var(tasklet_vec).list is assigned
to the next element of a temporary list ( t->next ). Is it possible
for __get_cpu_var(tasklet_vec).list to get populated during a call to
tasklet_action() or is what I am seeing just a NULL assignment to
t->next ?
On 10/22/07, Tony Mouawad <tonym.ace@xxxxxxxxx> wrote:
> Hello,
>
> I'm trying to get a handle on a problem that is occuring inside of a
> call to tasklet_action(). Can someone explain a bit about what line
> 404 is doing ( and the function itself ) in the following code? It
> seems that the OS is intermittently resulting in a false result on
> line 404 and then executing line 405 which ultimately halts the
> kernel.
>
> Regards,
> Tony
>
>
> 388 static void tasklet_action(struct softirq_action *a)
> 389 {
> 390 struct tasklet_struct *list;
> 391
> 392 local_irq_disable();
> 393 list = __get_cpu_var(tasklet_vec).list;
> 394 __get_cpu_var(tasklet_vec).list = NULL;
> 395 local_irq_enable();
> 396
> 397 while (list) {
> 398 struct tasklet_struct *t = list;
> 399
> 400 list = list->next;
> 401
> 402 if (tasklet_trylock(t)) {
> 403 if (!atomic_read(&t->count)) {
> 404 if
> (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
> 405 BUG();
> 406 t->func(t->data);
> 407 tasklet_unlock(t);
> 408 continue;
> 409 }
> 410 tasklet_unlock(t);
> 411 }
> 412
> 413 local_irq_disable();
> 414 t->next = __get_cpu_var(tasklet_vec).list;
> 415 __get_cpu_var(tasklet_vec).list = t;
> 416 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
> 417 local_irq_enable();
> 418 }
> 419 }
>
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