Hi Will,
On Tue, 26 Jan 2021 at 19:48, Will Deacon <w...@kernel.org> wrote:
>
> Hi Sumit,
>
> On Fri, Jan 15, 2021 at 05:31:41PM +0530, Sumit Garg wrote:
> > With the recent feature added to enable perf events to use pseudo NMIs
> > as interrupts on platforms which support GICv3 or later, its now been
> > possible to enable hard lockup detector (or NMI watchdog) on arm64
> > platforms. So enable corresponding support.
> >
> > One thing to note here is that normally lockup detector is initialized
> > just after the early initcalls but PMU on arm64 comes up much later as
> > device_initcall(). So we need to re-initialize lockup detection once
> > PMU has been initialized.
> >
> > Signed-off-by: Sumit Garg <sumit.g...@linaro.org>
> > ---
>
> [...]
>
> > diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> > index 3605f77a..bafb7c8 100644
> > --- a/arch/arm64/kernel/perf_event.c
> > +++ b/arch/arm64/kernel/perf_event.c
> > @@ -23,6 +23,8 @@
> > #include <linux/platform_device.h>
> > #include <linux/sched_clock.h>
> > #include <linux/smp.h>
> > +#include <linux/nmi.h>
> > +#include <linux/cpufreq.h>
> >
> > /* ARMv8 Cortex-A53 specific event types. */
> > #define ARMV8_A53_PERFCTR_PREF_LINEFILL 0xC2
> > @@ -1246,12 +1248,30 @@ static struct platform_driver armv8_pmu_driver = {
> > .probe = armv8_pmu_device_probe,
> > };
> >
> > +static int __init lockup_detector_init_fn(void *data)
> > +{
> > + lockup_detector_init();
> > + return 0;
> > +}
> > +
> > static int __init armv8_pmu_driver_init(void)
> > {
> > + int ret;
> > +
> > if (acpi_disabled)
> > - return platform_driver_register(&armv8_pmu_driver);
> > + ret = platform_driver_register(&armv8_pmu_driver);
> > else
> > - return arm_pmu_acpi_probe(armv8_pmuv3_init);
> > + ret = arm_pmu_acpi_probe(armv8_pmuv3_init);
> > +
> > + /*
> > + * Try to re-initialize lockup detector after PMU init in
> > + * case PMU events are triggered via NMIs.
> > + */
> > + if (ret == 0 && arm_pmu_irq_is_nmi())
> > + smp_call_on_cpu(raw_smp_processor_id(),
> > lockup_detector_init_fn,
> > + NULL, false);
> > +
> > + return ret;
>
> What's wrong with the alternative approach outlined by Mark:
>
> https://lore.kernel.org/r/20210113130235.GB19011@C02TD0UTHF1T.local
>
> ?
I have replied on this thread.
-Sumit
>
> Will
