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    Subject[PATCH 4/4] [RFC][powerpc] nmi_watchdog: support for powerpc
    Date
    In order to make sure other arches compiled properly, I used powerpc as a
    test bed. It was just basic sanity checking code to see if the
    infrastructure bits worked ok. The lock up detection logic is non-existant
    and the sample_period is some large made up number.

    The interesting piece of the patch is the change to ppc970-pmc.c. I had to
    move the initcall from arch_init to early_init to allow the nmi_watchdog to
    register with the perf_event subsystem as cpus were coming online.
    Otherwise it failed with ENXIO.

    This patch is just a conversation starter. I am not sure if powerpc has a
    true NMI and if this is really needed. But since I spent some time making
    it work, I thought I would throw it out there.

    Signed-off-by: Don Zickus <dzickus@redhat.com>
    ---
    arch/powerpc/Kconfig | 1 +
    arch/powerpc/kernel/Makefile | 1 +
    arch/powerpc/kernel/hw_nmi.c | 45 ++++++++++++++++++++++++++++++++++++++
    arch/powerpc/kernel/ppc970-pmu.c | 2 +-
    4 files changed, 48 insertions(+), 1 deletions(-)
    create mode 100644 arch/powerpc/kernel/hw_nmi.c

    diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
    index ba3948c..146b0b5 100644
    --- a/arch/powerpc/Kconfig
    +++ b/arch/powerpc/Kconfig
    @@ -140,6 +140,7 @@ config PPC
    select HAVE_SYSCALL_WRAPPERS if PPC64
    select GENERIC_ATOMIC64 if PPC32
    select HAVE_PERF_EVENTS
    + select PERF_EVENTS_NMI

    config EARLY_PRINTK
    bool
    diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
    index c002b04..08e3d2d 100644
    --- a/arch/powerpc/kernel/Makefile
    +++ b/arch/powerpc/kernel/Makefile
    @@ -86,6 +86,7 @@ obj-$(CONFIG_KPROBES) += kprobes.o
    obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
    obj-$(CONFIG_STACKTRACE) += stacktrace.o
    obj-$(CONFIG_SWIOTLB) += dma-swiotlb.o
    +obj-$(CONFIG_NMI_WATCHDOG) += hw_nmi.o

    pci64-$(CONFIG_PPC64) += pci_dn.o isa-bridge.o
    obj-$(CONFIG_PCI) += pci_$(CONFIG_WORD_SIZE).o $(pci64-y) \
    diff --git a/arch/powerpc/kernel/hw_nmi.c b/arch/powerpc/kernel/hw_nmi.c
    new file mode 100644
    index 0000000..2313724
    --- /dev/null
    +++ b/arch/powerpc/kernel/hw_nmi.c
    @@ -0,0 +1,45 @@
    +/*
    + * HW NMI watchdog support
    + *
    + * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
    + *
    + * Arch specific calls to support NMI watchdog
    + *
    + * Bits copied from original nmi.c file
    + *
    + */
    +
    +#include <linux/smp.h>
    +//#include <linux/cpumask.h>
    +//#include <linux/sched.h>
    +#include <linux/percpu.h>
    +#include <linux/kernel_stat.h>
    +
    +//#include <linux/nmi.h>
    +
    +static DEFINE_PER_CPU(unsigned, last_irq_sum);
    +
    +int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
    +{
    + unsigned int sum;
    + int cpu = smp_processor_id();
    +
    + /* We determine if the cpu is stuck by checking whether any
    + * interrupts have happened since we last checked. Of course
    + * an nmi storm could create false positives, but the higher
    + * level logic should account for that
    + */
    + return 0;
    + sum = kstat_irqs_cpu(0, cpu);
    + if (__get_cpu_var(last_irq_sum) == sum) {
    + return 1;
    + } else {
    + __get_cpu_var(last_irq_sum) = sum;
    + return 0;
    + }
    +}
    +
    +u64 hw_nmi_get_sample_period(void)
    +{
    + return 10000 * 1000;
    +}
    diff --git a/arch/powerpc/kernel/ppc970-pmu.c b/arch/powerpc/kernel/ppc970-pmu.c
    index 8eff48e..d91aaf1 100644
    --- a/arch/powerpc/kernel/ppc970-pmu.c
    +++ b/arch/powerpc/kernel/ppc970-pmu.c
    @@ -492,4 +492,4 @@ static int init_ppc970_pmu(void)
    return register_power_pmu(&ppc970_pmu);
    }

    -arch_initcall(init_ppc970_pmu);
    +early_initcall(init_ppc970_pmu);
    --
    1.6.6.83.gc9a2


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