Re: [PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier

Don Zickus
2010-04-21T21:10:57Z

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