Messages in this thread |  | | Date | Mon, 19 Jan 2015 17:48:18 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [RFC PATCH 5/5] arm: perf: Use FIQ to handle PMU events. |
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On Tue, Jan 13, 2015 at 04:35:31PM +0000, Daniel Thompson wrote: > +/* > + * This handler is called *unconditionally* from the default NMI/FIQ > + * handler. The irq may not be anything to do with us so the main > + * job of this function is to figure out if the irq passed in is ours > + * or not. > + */ > +void cpu_pmu_handle_fiq(int irq) > +{ > + int cpu = smp_processor_id();
This can be either debug_smp_processor_id() or raw_smp_processor_id(). raw_smp_processor_id() is fine from FIQ contexts, as seems to be debug_smp_processor_id(), but only because we guarantee that irqs_disabled() in there will be true.
> + > + if (irq != get_cpu_var(cpu_pmu_irqs)) > + return;
get_cpu_var() needs put_cpu_var() to undo its effects. get_cpu_var() calls preempt_disable(), which calls into lockdep... I think we determined that was fine last time we went digging? put_cpu_var() would call preempt_enable() which I'd hope would be safe in FIQ/NMI contexts?
> + > + (void)armpmu_dispatch_irq(irq, > + get_cpu_ptr(&cpu_pmu->hw_events->percpu_pmu));
Again, get_cpu_xxx() needs to be balanced with a put_cpu_xxx().
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