[PATCH 1/2] x86: add config option for the default NMI watchdog

[Aristeu Rozanski <aris@redhat.com>]

This patch adds config options to allow selecting one of the two NMI watchdog
methods as default. It's still possible to select a different method or even
disable it using the command line mode. This is required for the next patch,
which adds support to "auto" mode.

Signed-off-by: Aristeu Rozanski <aris@redhat.com>
---
 arch/x86/kernel/apic/nmi.c |   11 ++++++++++-
 lib/Kconfig.debug          |   21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index e82a450..fd176e9 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -50,7 +50,16 @@ static cpumask_var_t backtrace_mask;
 atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
 EXPORT_SYMBOL(nmi_active);
 
-unsigned int nmi_watchdog = NMI_NONE;
+#ifdef CONFIG_DEBUG_DEFAULT_NMI_NONE
+#define DEFAULT_NMI_WATCHDOG_VALUE NMI_NONE
+#endif
+#ifdef CONFIG_DEBUG_DEFAULT_NMI_IOAPIC
+#define DEFAULT_NMI_WATCHDOG_VALUE NMI_IOAPIC
+#endif
+#ifdef CONFIG_DEBUG_DEFAULT_NMI_LAPIC
+#define DEFAULT_NMI_WATCHDOG_VALUE NMI_LAPIC
+#endif
+unsigned int nmi_watchdog = DEFAULT_NMI_WATCHDOG_VALUE;
 EXPORT_SYMBOL(nmi_watchdog);
 
 static int panic_on_timeout;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2790b4f..0a3622a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -253,6 +253,27 @@ config DEBUG_NMI_TIMEOUT
 	  This value is the number of seconds the NMI watchdog will tick
 	  before it decides the machine has hung.
 
+choice
+	prompt "Default NMI watchdog method"
+	default DEBUG_DEFAULT_NMI_NONE
+	depends on X86
+	help
+	  This allows to set the default NMI watchdog method to be used. The
+	  default can be changed using nmi_watchdog=. Only choose an option
+	  different from Disabled if you know the machine supports that method.
+
+config DEBUG_DEFAULT_NMI_NONE
+	bool "Disabled"
+
+config DEBUG_DEFAULT_NMI_IOAPIC
+	bool "IOAPIC"
+
+config DEBUG_DEFAULT_NMI_LAPIC
+	bool "LAPIC"
+
+endchoice
+
+
 config TIMER_STATS
 	bool "Collect kernel timers statistics"
 	depends on DEBUG_KERNEL && PROC_FS
-- 
1.5.5.6