[for-next][PATCH 8/8] tracing/fgraph: Have wakeup and irqsoff tracers ignore graph functions too

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

Currently both the wakeup and irqsoff traces do not handle set_graph_notrace
well. The ftrace infrastructure will ignore the return paths of all
functions leaving them hanging without an end:

  # echo '*spin*' > set_graph_notrace
  # cat trace
  [...]
          _raw_spin_lock() {
            preempt_count_add() {
            do_raw_spin_lock() {
          update_rq_clock();

Where the '*spin*' functions should have looked like this:

          _raw_spin_lock() {
            preempt_count_add();
            do_raw_spin_lock();
          }
          update_rq_clock();

Instead, have the wakeup and irqsoff tracers ignore the functions that are
set by the set_graph_notrace like the function_graph tracer does. Move
the logic in the function_graph tracer into a header to allow wakeup and
irqsoff tracers to use it as well.

Cc: Namhyung Kim <namhyung.kim@xxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.h                 | 11 +++++++++++
 kernel/trace/trace_functions_graph.c | 14 +++++++-------
 kernel/trace/trace_irqsoff.c         | 12 ++++++++++++
 kernel/trace/trace_sched_wakeup.c    | 12 ++++++++++++
 4 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 37602e722336..c2234494f40c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -846,6 +846,17 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr)
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */
+
+extern unsigned int fgraph_max_depth;
+
+static inline bool ftrace_graph_ignore_func(struct ftrace_graph_ent *trace)
+{
+	/* trace it when it is-nested-in or is a function enabled. */
+	return !(trace->depth || ftrace_graph_addr(trace->func)) ||
+		(trace->depth < 0) ||
+		(fgraph_max_depth && trace->depth >= fgraph_max_depth);
+}
+
 #else /* CONFIG_FUNCTION_GRAPH_TRACER */
 static inline enum print_line_t
 print_graph_function_flags(struct trace_iterator *iter, u32 flags)
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 566f7327c3aa..d56123cdcc89 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -65,7 +65,7 @@ struct fgraph_data {
 
 #define TRACE_GRAPH_INDENT	2
 
-static unsigned int max_depth;
+unsigned int fgraph_max_depth;
 
 static struct tracer_opt trace_opts[] = {
 	/* Display overruns? (for self-debug purpose) */
@@ -384,10 +384,10 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	if (!ftrace_trace_task(tr))
 		return 0;
 
-	/* trace it when it is-nested-in or is a function enabled. */
-	if ((!(trace->depth || ftrace_graph_addr(trace->func)) ||
-	     ftrace_graph_ignore_irqs()) || (trace->depth < 0) ||
-	    (max_depth && trace->depth >= max_depth))
+	if (ftrace_graph_ignore_func(trace))
+		return 0;
+
+	if (ftrace_graph_ignore_irqs())
 		return 0;
 
 	/*
@@ -1500,7 +1500,7 @@ graph_depth_write(struct file *filp, const char __user *ubuf, size_t cnt,
 	if (ret)
 		return ret;
 
-	max_depth = val;
+	fgraph_max_depth = val;
 
 	*ppos += cnt;
 
@@ -1514,7 +1514,7 @@ graph_depth_read(struct file *filp, char __user *ubuf, size_t cnt,
 	char buf[15]; /* More than enough to hold UINT_MAX + "\n"*/
 	int n;
 
-	n = sprintf(buf, "%d\n", max_depth);
+	n = sprintf(buf, "%d\n", fgraph_max_depth);
 
 	return simple_read_from_buffer(ubuf, cnt, ppos, buf, n);
 }
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 03cdff84d026..86654d7e1afe 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -175,6 +175,18 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
 	int ret;
 	int pc;
 
+	if (ftrace_graph_ignore_func(trace))
+		return 0;
+	/*
+	 * Do not trace a function if it's filtered by set_graph_notrace.
+	 * Make the index of ret stack negative to indicate that it should
+	 * ignore further functions.  But it needs its own ret stack entry
+	 * to recover the original index in order to continue tracing after
+	 * returning from the function.
+	 */
+	if (ftrace_graph_notrace_addr(trace->func))
+		return 1;
+
 	if (!func_prolog_dec(tr, &data, &flags))
 		return 0;
 
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 1bf2324dc682..5d0bb025bb21 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -239,6 +239,18 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
 	unsigned long flags;
 	int pc, ret = 0;
 
+	if (ftrace_graph_ignore_func(trace))
+		return 0;
+	/*
+	 * Do not trace a function if it's filtered by set_graph_notrace.
+	 * Make the index of ret stack negative to indicate that it should
+	 * ignore further functions.  But it needs its own ret stack entry
+	 * to recover the original index in order to continue tracing after
+	 * returning from the function.
+	 */
+	if (ftrace_graph_notrace_addr(trace->func))
+		return 1;
+
 	if (!func_prolog_preempt_disable(tr, &data, &pc))
 		return 0;
 
-- 
2.10.2