x86: Move trigger_all_cpu_backtrace to its own die_notifier

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.

V2:
- use arch_spin_locks

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
LKML-Reference: <1273266711-18706-6-git-send-email-dzickus@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 79425f96fceebbf0946478f4617778c4aba182c6..8c3edfb89c2be3d3a9a83920d0d4c9561c24539d 100644 (file)
--- 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 arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
+
+               arch_spin_lock(&lock);
+               printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
+               show_regs(regs);
+               dump_stack();
+               arch_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 */