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

Frederic Weisbecker
2010-04-21T21:00:00Z

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.

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

> + 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));
> + return NOTIFY_STOP;
> + }
> +
> + return NOTIFY_DONE;
> +}
> +
> +static __read_mostly struct notifier_block backtrace_notifier = {
> + .notifier_call = arch_trigger_all_cpu_backtrace_handler,
> + .next = NULL,
> + .priority = 1
> +};
> +
> +static int __init register_trigger_all_cpu_backtrace(void)
> +{
> + register_die_notifier(&backtrace_notifier);
> + return 0;
> +}
> +early_initcall(register_trigger_all_cpu_backtrace);
> #endif
>
> /* STUB calls to mimic old nmi_watchdog behaviour */
> --
> 1.6.5.2
>