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    SubjectRe: [PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier
    On Wed, Apr 21, 2010 at 11:00:04PM +0200, Frederic Weisbecker wrote:
    > On Tue, Apr 20, 2010 at 11:24:02AM -0400, Don Zickus wrote:
    > > As part of the transition of the nmi watchdog to something more generic,
    > > the trigger_all_cpu_backtrace code is getting left behind. Put it in its
    > > own die_notifier so it can still be used.
    > >
    > > Signed-off-by: Don Zickus <dzickus@redhat.com>
    > > ---
    > > arch/x86/kernel/apic/hw_nmi.c | 65 ++++++++++++++++++++++++++++++++---------
    > > 1 files changed, 51 insertions(+), 14 deletions(-)
    > >
    > > diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
    > > index 79425f9..19d3435 100644
    > > --- a/arch/x86/kernel/apic/hw_nmi.c
    > > +++ b/arch/x86/kernel/apic/hw_nmi.c
    > > @@ -17,6 +17,10 @@
    > > #include <linux/cpumask.h>
    > > #include <linux/kernel_stat.h>
    > > #include <asm/mce.h>
    > > +#include <linux/kdebug.h>
    > > +#include <linux/notifier.h>
    > > +#include <linux/kprobes.h>
    > > +
    > >
    > > #include <linux/nmi.h>
    > > #include <linux/module.h>
    > > @@ -54,20 +58,6 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
    > > unsigned int sum;
    > > int cpu = smp_processor_id();
    > >
    > > - /* FIXME: cheap hack for this check, probably should get its own
    > > - * die_notifier handler
    > > - */
    > > - if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
    > > - static DEFINE_SPINLOCK(lock); /* Serialise the printks */
    > > -
    > > - spin_lock(&lock);
    > > - printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
    > > - show_regs(regs);
    > > - dump_stack();
    > > - spin_unlock(&lock);
    > > - cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
    > > - }
    > > -
    > > /* if we are doing an mce, just assume the cpu is not stuck */
    > > /* Could check oops_in_progress here too, but it's safer not to */
    > > if (mce_in_progress())
    > > @@ -109,6 +99,53 @@ void arch_trigger_all_cpu_backtrace(void)
    > > mdelay(1);
    > > }
    > > }
    > > +
    > > +static int __kprobes
    > > +arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
    > > + unsigned long cmd, void *__args)
    > > +{
    > > + struct die_args *args = __args;
    > > + struct pt_regs *regs;
    > > + int cpu = smp_processor_id();
    > > +
    > > + switch (cmd) {
    > > + case DIE_NMI:
    > > + case DIE_NMI_IPI:
    > > + break;
    > > +
    > > + default:
    > > + return NOTIFY_DONE;
    > > + }
    > > +
    > > + regs = args->regs;
    > > +
    > > + if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
    > > + static DEFINE_SPINLOCK(lock); /* Serialise the printks */
    > > +
    > > + spin_lock(&lock);
    >
    >
    >
    > This should be an arch_spin_lock(), so that it won't sleep with rt mutex.

    ok, I just copied and pasted what was there currently.

    >
    >
    > In fact this whole function can be moved to generic code, right?

    generic for x86, yes. Ingo stuck in the nmi.c code awhile ago. This code
    just needs a home somewhere. I really don't care where.

    Cheers,
    Don


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