Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes: > On Fri, 10 Jul 2015, Stephen Warren wrote: >> On 07/07/2015 03:13 PM, Eric Anholt wrote: >> > +static void bcm2836_mask_per_cpu_irq(unsigned int reg, unsigned int bit) >> > +{ >> > + void __iomem *reg_base = intc.base + reg; >> > + unsigned int i; >> > + >> > + for (i = 0; i < 4; i++) >> >> Is "4" there the CPU count? Perhaps this should use one of the Linux >> APIs to query the CPU count rather than hard-coding it? >> >> Should per-CPU IRQs automatically be masked on all CPUs at once, or only >> on the current CPU? A very quick look at the ARM GIC driver implies it >> doesn't iterate over all CPUs when masking per-CPU IRQs. > > Usually per cpu interrupts are only masked on the cpu which is calling > the function. The whole reason why per cpu interrupts exist is that > you can share the same interrupt number for all cores. > > So masking all interrupts is not a good idea. In this case if a cpu is > hot unplugged, then all other cpus would not longer get timer > interrupts. Not what you really want, right? I was replicating the behavior of the downstream driver, but it seemed suspicious. Converting to using smp_processor_id() to just mask/unmask this CPU's interrupts seems to have gone fine.
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