On 20/02/2008, Ahmed S. Darwish <[EMAIL PROTECTED]> wrote: > On Wed, Feb 20, 2008 at 11:41:13AM +0100, Ingo Molnar wrote: > > > > * Ahmed S. Darwish <[EMAIL PROTECTED]> wrote: > > > > > > > - local_irq_disable(); > > > > > - t->next = __get_cpu_var(tasklet_vec).list; > > > > > - __get_cpu_var(tasklet_vec).list = t; > > > > > - __raise_softirq_irqoff(TASKLET_SOFTIRQ); > > > > > - local_irq_enable(); > > > > > + /* We were not lucky enough to run, reschedule. */ > > > > > + __tasklet_schedule(t); > > > > > > > > i think there's a subtle difference that you missed: this one does > > > > __raise_softirq_irqoff(), while __tasklet_schedule() does a > > > > raise_softirq_irqoff(). (note the lack of undescores) > > > > > > > > the reason is to avoid infinitely self-activating tasklets. > > > > > > Indeed, thanks a lot for the explanation. (maybe it's time to check > > > for new eyeglasses ;)). > > > > nah, it's rather subtle and the code looked good to me at first but i > > remembered that there was some small detail here to watch out for. > > > > i really dont like tasklets due to their many, arbitrary scheduling > > limitations, we should really use the "turn tasklets into kthreads" > > patch i posted last year. > > > > While we are at it, there's a small question that is bothering me > for a while (and I'm really thankful for help). > > I keep reading that softirqs (and naturally, tasklets) got executed > in interrupt context at the return from hardirq code path. > > Checking entry_32.S, I find no mentioning of softirqs on the return > path (beginning from ret_from_intr: to restore_all: ) > > The only invocation I'm able to find is from local_bh_enable() and > from ksoftirqd/n threads (by calling do_softirq()). AFAIK, both > invocations occur in a _nont-interrupt_ context (exception context). > > So, where does the interrupt-context tasklets invocation really > occur ?
Look at irq_exit() in softirq.c. The common sequence is ... -> do_IRQ() --> irq_exit() --> invoke_softirq() -- Best regards, Dmitry Adamushko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
