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From: Don Zickus on 27 Jan 2010 15:10
These are the bits that enable the new nmi_watchdog and safely isolate the
old nmi_watchdog. Only one or the other can run, not both at the same
time.

Signed-off-by: Don Zickus <dzickus(a)redhat.com>
---
arch/x86/kernel/apic/Makefile | 7 ++++++-
arch/x86/kernel/traps.c | 2 ++
include/linux/nmi.h | 4 ++++
kernel/Makefile | 1 +
lib/Kconfig.debug | 13 +++++++++++++
5 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/Makefile b/arch/x86/kernel/apic/Makefile
index 565c1bf..1a4512e 100644
--- a/arch/x86/kernel/apic/Makefile
+++ b/arch/x86/kernel/apic/Makefile
@@ -2,7 +2,12 @@
# Makefile for local APIC drivers and for the IO-APIC code
#

-obj-$(CONFIG_X86_LOCAL_APIC) += apic.o apic_noop.o probe_$(BITS).o ipi.o nmi.o
+obj-$(CONFIG_X86_LOCAL_APIC) += apic.o apic_noop.o probe_$(BITS).o ipi.o
+ifneq ($(CONFIG_NMI_WATCHDOG),y)
+obj-$(CONFIG_X86_LOCAL_APIC) += nmi.o
+endif
+obj-$(CONFIG_NMI_WATCHDOG) += hw_nmi.o
+
obj-$(CONFIG_X86_IO_APIC) += io_apic.o
obj-$(CONFIG_SMP) += ipi.o

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 3b98dd3..eee1dc8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -406,6 +406,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
return;

#ifdef CONFIG_X86_LOCAL_APIC
+#ifndef CONFIG_NMI_WATCHDOG
/*
* Ok, so this is none of the documented NMI sources,
* so it must be the NMI watchdog.
@@ -413,6 +414,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
if (nmi_watchdog_tick(regs, reason))
return;
if (!do_nmi_callback(regs, cpu))
+#endif /* !CONFIG_NMI_WATCHDOG */
unknown_nmi_error(reason, regs);
#else
unknown_nmi_error(reason, regs);
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index b752e80..a42ff0b 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -47,4 +47,8 @@ static inline bool trigger_all_cpu_backtrace(void)
}
#endif

+#ifdef CONFIG_NMI_WATCHDOG
+int hw_nmi_is_cpu_stuck(struct pt_regs *);
+#endif
+
#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index 864ff75..8a5abe5 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
+obj-$(CONFIG_NMI_WATCHDOG) += nmi_watchdog.o
obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 25c3ed5..04a43a2 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -170,6 +170,19 @@ config DETECT_SOFTLOCKUP
can be detected via the NMI-watchdog, on platforms that
support it.)

+config NMI_WATCHDOG
+ bool "Detect Hard Lockups with an NMI Watchdog"
+ depends on DEBUG_KERNEL && PERF_EVENTS
+ default y
+ help
+ Say Y here to enable the kernel to use the NMI as a watchdog
+ to detect hard lockups. This is useful when a cpu hangs for no
+ reason but can still respond to NMIs. A backtrace is displayed
+ for reviewing and reporting.
+
+ The overhead should be minimal, just an extra NMI every few
+ seconds.
+
config BOOTPARAM_SOFTLOCKUP_PANIC
bool "Panic (Reboot) On Soft Lockups"
depends on DETECT_SOFTLOCKUP
--
1.6.5.2

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