[PATCH v2][GIT PULL] tracing: add trace_stack interface

From: Steven Rostedt
Date: Tue May 19 2009 - 21:09:50 EST



Ingo,

I rebased because I forgot to add EXPORT_SYMBOL_GPL.

-- Steve

Please pull the latest tip/tracing/ftrace tree, which can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/ftrace


Steven Rostedt (1):
tracing: add trace_stack interface

----
include/linux/kernel.h | 2 ++
kernel/trace/trace.c | 16 ++++++++++++++++
2 files changed, 18 insertions(+), 0 deletions(-)
---------------------------
commit 9f6b28655254b91c48f684b367ac14bfec0e180a
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
Date: Tue May 19 18:54:16 2009 -0400

tracing: add trace_stack interface

This patch adds the global function

void trace_stack(void)

This allows a developer to find where a function is called. For example,
if you want to know who calls __netif_reschedule, you can add

static inline void __netif_reschedule(struct Qdisc *q)
{
struct softnet_data *sd;
unsigned long flags;

+ trace_stack();
local_irq_save(flags);
sd = &__get_cpu_var(softnet_data);
q->next_sched = sd->output_queue;

And see the following in the trace output:

<= __ftrace_trace_stack
<= trace_stack
<= __netif_schedule
<= dev_watchdog
<= run_timer_softirq
<= __do_softirq
<= call_softirq
<= do_softirq
<= irq_exit

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 883cd44..347a0f1 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -511,6 +511,7 @@ extern int
__ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);

extern void ftrace_dump(void);
+extern void trace_stack(void);
#else
static inline void
ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { }
@@ -531,6 +532,7 @@ ftrace_vprintk(const char *fmt, va_list ap)
return 0;
}
static inline void ftrace_dump(void) { }
+static inline void trace_stack(void) { }
#endif /* CONFIG_TRACING */

/*
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dd40d23..7bfd4f2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1046,6 +1046,22 @@ void __trace_stack(struct trace_array *tr,
__ftrace_trace_stack(tr, flags, skip, pc);
}

+/**
+ * trace_stack - dump the stack into the trace buffer
+ *
+ * Use this to record the stack trace into the ring buffer. If you
+ * want to know a caller of a function, place a call to trace_stack
+ * and the ftrace trace file will display who the callers were.
+ */
+void trace_stack(void)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+ __trace_stack(&global_trace, flags, 0, preempt_count());
+}
+EXPORT_SYMBOL_GPL(trace_stack);
+
static void ftrace_trace_userstack(struct trace_array *tr,
unsigned long flags, int pc)
{


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