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Subject[patch 3/5] x86, ftrace, hw-branch-tracer: dump on oops
Dump the branch trace on an oops (based on ftrace_dump_on_oops).

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
---
Index: ftrace/arch/x86/kernel/dumpstack.c
===================================================================
--- ftrace.orig/arch/x86/kernel/dumpstack.c 2009-01-14 15:21:46.000000000 +0100
+++ ftrace/arch/x86/kernel/dumpstack.c 2009-01-14 15:26:11.000000000 +0100
@@ -14,6 +14,7 @@
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>
+#include <linux/ftrace.h>

#include <asm/stacktrace.h>

@@ -195,6 +196,11 @@
int cpu;
unsigned long flags;

+ /* notify the hw-branch tracer so it may disable tracing and
+ add the last trace to the trace buffer -
+ the earlier this happens, the more useful the trace. */
+ trace_hw_branch_oops();
+
oops_enter();

/* racy, but better than risking deadlock. */
Index: ftrace/kernel/trace/trace.h
===================================================================
--- ftrace.orig/kernel/trace/trace.h 2009-01-14 15:21:46.000000000 +0100
+++ ftrace/kernel/trace/trace.h 2009-01-14 15:26:11.000000000 +0100
@@ -415,7 +415,6 @@

void trace_graph_return(struct ftrace_graph_ret *trace);
int trace_graph_entry(struct ftrace_graph_ent *trace);
-void trace_hw_branch(struct trace_array *tr, u64 from, u64 to);

void tracing_start_cmdline_record(void);
void tracing_stop_cmdline_record(void);
Index: ftrace/kernel/trace/trace_hw_branches.c
===================================================================
--- ftrace.orig/kernel/trace/trace_hw_branches.c 2009-01-14 15:26:07.000000000 +0100
+++ ftrace/kernel/trace/trace_hw_branches.c 2009-01-14 15:26:11.000000000 +0100
@@ -39,6 +39,7 @@
#define this_buffer per_cpu(buffer, smp_processor_id())

static int __read_mostly trace_hw_branches_enabled;
+static struct trace_array *hw_branch_trace __read_mostly;


/*
@@ -127,6 +128,8 @@

static int bts_trace_init(struct trace_array *tr)
{
+ hw_branch_trace = tr;
+
register_hotcpu_notifier(&bts_hotcpu_notifier);
tracing_reset_online_cpus(tr);
bts_trace_start(tr);
@@ -138,6 +141,8 @@
{
bts_trace_stop(tr);
unregister_hotcpu_notifier(&bts_hotcpu_notifier);
+
+ hw_branch_trace = NULL;
}

static void bts_trace_print_header(struct seq_file *m)
@@ -166,8 +171,9 @@
return TRACE_TYPE_UNHANDLED;
}

-void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
+void trace_hw_branch(u64 from, u64 to)
{
+ struct trace_array *tr = hw_branch_trace;
struct ring_buffer_event *event;
struct hw_branch_entry *entry;
unsigned long irq1, irq2;
@@ -200,8 +206,7 @@
local_irq_restore(irq1);
}

-static void trace_bts_at(struct trace_array *tr,
- const struct bts_trace *trace, void *at)
+static void trace_bts_at(const struct bts_trace *trace, void *at)
{
struct bts_struct bts;
int err = 0;
@@ -216,7 +221,7 @@

switch (bts.qualifier) {
case BTS_BRANCH:
- trace_hw_branch(tr, bts.variant.lbr.from, bts.variant.lbr.to);
+ trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
break;
}
}
@@ -232,12 +237,15 @@
const struct bts_trace *trace;
unsigned char *at;

- if (!this_tracer)
+ if (unlikely(!tr))
return;

if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
return;

+ if (unlikely(!this_tracer))
+ return;
+
ds_suspend_bts(this_tracer);
trace = ds_read_bts(this_tracer);
if (!trace)
@@ -245,11 +253,11 @@

for (at = trace->ds.top; (void *)at < trace->ds.end;
at += trace->ds.size)
- trace_bts_at(tr, trace, at);
+ trace_bts_at(trace, at);

for (at = trace->ds.begin; (void *)at < trace->ds.top;
at += trace->ds.size)
- trace_bts_at(tr, trace, at);
+ trace_bts_at(trace, at);

out:
ds_resume_bts(this_tracer);
@@ -264,6 +272,15 @@
mutex_unlock(&bts_tracer_mutex);
}

+void trace_hw_branch_oops(void)
+{
+ mutex_lock(&bts_tracer_mutex);
+
+ trace_bts_cpu(hw_branch_trace);
+
+ mutex_unlock(&bts_tracer_mutex);
+}
+
struct tracer bts_tracer __read_mostly =
{
.name = "hw-branch-tracer",
Index: ftrace/include/linux/ftrace.h
===================================================================
--- ftrace.orig/include/linux/ftrace.h 2009-01-14 15:21:46.000000000 +0100
+++ ftrace/include/linux/ftrace.h 2009-01-14 15:26:11.000000000 +0100
@@ -492,4 +492,17 @@

#endif /* CONFIG_TRACING */

+
+#ifdef CONFIG_HW_BRANCH_TRACER
+
+void trace_hw_branch(u64 from, u64 to);
+void trace_hw_branch_oops(void);
+
+#else /* CONFIG_HW_BRANCH_TRACER */
+
+static inline void trace_hw_branch(u64 from, u64 to) {}
+static inline void trace_hw_branch_oops(void) {}
+
+#endif /* CONFIG_HW_BRANCH_TRACER */
+
#endif /* _LINUX_FTRACE_H */
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