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 ? Thanks -- Ahmed S. Darwish Homepage: http://darwish.07.googlepages.com Blog: http://darwish-07.blogspot.com -- 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/
