On 09/17/2012 08:18 PM, Gilles Chanteperdrix wrote: > On 09/17/2012 08:15 PM, Jan Kiszka wrote: > >> On 2012-09-17 20:12, Jan Kiszka wrote: >>> On 2012-09-17 20:08, Gilles Chanteperdrix wrote: >>>> On 09/17/2012 08:05 PM, Jan Kiszka wrote: >>>> >>>>> On 2012-09-17 19:46, Gilles Chanteperdrix wrote: >>>>>> ipipe_end is a nop when called from primary domain, yes, but this is not >>>>>> very different from edge irqs. Also, fasteoi become a bit like MSI: in >>>>>> the same way as we can not mask MSI from primary domain, we should not >>>>>> mask IO-APIC fasteoi irqs, because the cost is too prohibitive. If we >>>>>> can live with MSI without masking them in primary mode, I guess we can >>>>>> do the same with fasteoi irqs. >>>>> >>>>> MSIs are edge triggered, fasteois are still level-based. They require >>>>> masking at the point you defer them - what we do and what Linux may even >>>>> extend beyond that. If you mask them by raising the task priority, you >>>>> have to keep it raised until Linux finally handled the IRQ. >>>> >>>> >>>> Yes. >>>> >>>>> Or you >>>>> decide to mask it at IO-APIC level again. >>>> >>>> >>>> We do not want that. >>>> >>>>> If you keep the TPR raised, >>>>> you will block more than what Linux wants to block. >>>> >>>> >>>> The point is that if the TPR keeps raised, it means that primary domain >>>> has preempted Linux, so, we want it to keep that way. Otherwise the TPR >>>> gets lowered when Linux has handled the interrupt. >>>> >>>> A week-end of testing made me sure of one thing: it works. I assure you. >>> >>> Probably, in the absence of IRQF_ONESHOT Linux interrupts. No longer if >>> you face threaded IRQs - I assure you. >> >> Well, it may work (if mask/unmask callbacks work as native) but the >> benefit is gone: masking at IO-APIC level will be done again. Given that >> threaded IRQs become increasingly popular, it will also be hard to avoid >> them in common setups. > > > The thing is, if we no longer use the IO-APIC spinlock from primary > domain, we may not have to turn it into an ipipe_spinlock, and may be > able to preempt the IO-APIC masking. >
No, we need it in ack_apic_level in the IO-APIC erratum case. -- Gilles. _______________________________________________ Xenomai mailing list Xenomai@xenomai.org http://www.xenomai.org/mailman/listinfo/xenomai