Am 15.12.2010 14:04, Thomas Gleixner wrote: > On Wed, 15 Dec 2010, Jan Kiszka wrote: >> Am 14.12.2010 21:54, Thomas Gleixner wrote: >>> On Mon, 13 Dec 2010, Jan Kiszka wrote: >>>> @@ -943,6 +950,9 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id) >>>> /* Make sure it's not being used on another CPU: */ >>>> synchronize_irq(irq); >>>> >>>> + if (single_handler) >>>> + desc->irq_data.drv_status &= ~IRQS_SHARED; >>>> + >>> >>> What's the reason to clear this flag outside of the desc->lock held >>> region. >> >> We need to synchronize the irq first before clearing the flag. >> >> The problematic scenario behind this: An IRQ started in shared mode, >> this the line was unmasked after the hardirq. Now we clear IRQS_SHARED >> before calling into the threaded handler. And that handler may now think >> that the line is still masked as IRQS_SHARED is set. > > That should read "not set" I guess. Can't remember who wrote this, but that guy might have been too tired for clear sentences: Yes, of course, we could run into troubles, if IRQS_SHARED was _not_ set while the IRQ line is unmasked between hard and threaded handler. > Hmm, needs more thoughts :( Be warned, might be painful. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
