On Thu, 7 Sep 2017, Paul Burton wrote: > Up until now per_cpu_devid interrupts have not supported sharing. On > MIPS we have some percpu interrupts which are shared in many systems - > a single CPU interrupt line may be used to indicate a timer interrupt, > performance counter interrupt or fast debug channel interrupt. We have > up until now supported this with a series of hacks, wherein drivers call > each other's interrupt handlers & our MIPS GIC irqchip driver includes a > hack which configures the interrupt(s) for all CPUs. In order to allow > this mess to be cleaned up, this patch introduces support for shared > per_cpu_devid interrupts. > > The major portion of this is supporting per_cpu_devid interrupts in > __handle_irq_event_percpu() and then making use of this, via > handle_irq_event_percpu(), from handler_percpu_devif_irq() to invoke the > handler for all actions associated with the shared interrupt. This does > have a few side effects worth noting: > > - per_cpu_devid interrupts will now add to the entropy pool via > add_interrupt_randomness(), where they previously did not. > > - per_cpu_devid interrupts will record timings when IRQS_TIMINGS is > set, via record_irq_time(), where they previously did not. > > - per_cpu_devid interrupts will handle an IRQ_WAKE_THREAD return from > their handlers to wake a thread, where they previously did not. That's broken because it lacks the magic synchronization which is described in the comment in __irq_wake_thread(). > I'm not aware of any reason the above should be bad side effects, so > sharing __handle_irq_event_percpu() for per_cpu_devid interrupts seems > like a positive. Now you are :) The other side effect of this is the extra overhead. You add an extra conditional into the main interrupt handling function __handle_irq_event_percpu() and the extra loop and hoops overhead for handle_percpu_devid_irq(). Thanks, tglx
