Andrew Morton pointed out that some archs do not compile the ftrace code
because their NMI code does not define a DIE_OOPS. The ftrace dump_on_oops
code adds an NMI handler to dump out the contents of the buffer if we
hit an oops or a NMI detected lockup.

The NMI handlers are called for other reasons than DIE_OOPS so the ftrace
handler must distinguish between them. This patch creates a "weak" handler
that does nothing and lets the arch define the NMI handler for ftrace.

Signed-off-by: Steven Rostedt
---
arch/x86/kernel/Makefile | 2 +-
arch/x86/kernel/ftrace.c | 17 +++++++++++++++++
kernel/trace/trace.c | 27 +++++++++++++++------------
3 files changed, 33 insertions(+), 13 deletions(-)

Index: linux-tip.git/arch/x86/kernel/Makefile
================================================== =================
--- linux-tip.git.orig/arch/x86/kernel/Makefile 2008-10-23 12:55:19.000000000 -0400
+++ linux-tip.git/arch/x86/kernel/Makefile 2008-10-23 15:23:06.000000000 -0400
@@ -65,7 +65,7 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-$(CONFIG_X86_LOCAL_APIC) += apic.o nmi.o
obj-$(CONFIG_X86_IO_APIC) += io_apic.o
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
-obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+obj-$(CONFIG_TRACING) += ftrace.o
obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
Index: linux-tip.git/arch/x86/kernel/ftrace.c
================================================== =================
--- linux-tip.git.orig/arch/x86/kernel/ftrace.c 2008-10-23 12:55:19.000000000 -0400
+++ linux-tip.git/arch/x86/kernel/ftrace.c 2008-10-23 15:25:40.000000000 -0400
@@ -14,13 +14,29 @@
#include
#include
#include
+#include
#include
#include

#include
#include

+int ftrace_nmi_die_handler(struct notifier_block *self,
+ unsigned long val,
+ void *data)
+{
+ switch (val) {
+ case DIE_OOPS:
+ if (ftrace_dump_on_oops)
+ ftrace_dump();
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}

+#ifdef CONFIG_DYNAMIC_FTRACE
/* Long is fine, even if it is only 4 bytes ;-) */
static unsigned long *ftrace_nop;

@@ -171,3 +187,4 @@ int __init ftrace_dyn_arch_init(void *da

return 0;
}
+#endif /* CONFIG_DYNAMIC_FTRACE */
Index: linux-tip.git/kernel/trace/trace.c
================================================== =================
--- linux-tip.git.orig/kernel/trace/trace.c 2008-10-23 14:24:28.000000000 -0400
+++ linux-tip.git/kernel/trace/trace.c 2008-10-23 15:49:54.000000000 -0400
@@ -3051,23 +3051,26 @@ static struct notifier_block trace_panic
.priority = 150 /* priority: INT_MAX >= x >= 0 */
};

-static int trace_die_handler(struct notifier_block *self,
- unsigned long val,
- void *data)
+/**
+ * ftrace_nmi_die_handler - handler to call by ftrace on NMI lockup
+ * @self: unused
+ * @val: NMI handler type variable
+ * @data: unused
+ *
+ * Architectures need to define their own NMI watchdog handler.
+ * The NMI handlers may be called for various reasons, but we
+ * only want to dump the ftrace buffers when it is a lockup.
+ * Unfortunately, not all architectures define DIE_OOPS.
+ */
+int __weak ftrace_nmi_die_handler(struct notifier_block *self,
+ unsigned long val,
+ void *data)
{
- switch (val) {
- case DIE_OOPS:
- if (ftrace_dump_on_oops)
- ftrace_dump();
- break;
- default:
- break;
- }
return NOTIFY_OK;
}

static struct notifier_block trace_die_notifier = {
- .notifier_call = trace_die_handler,
+ .notifier_call = ftrace_nmi_die_handler,
.priority = 200
};


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