linux-kernel - [PATCH] trace: function graph: Fix filters for function

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Date:	Sat,  4 Jun 2016 17:01:07 -0700
From:	Joel Fernandes <agnel.joel@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH] trace: function graph: Fix filters for function_graph threshold

Function graph tracer currently ignores filters if tracing_thresh is set.
For example, even if set_ftrace_pid is set, then its ignored if tracing_thresh
set, resulting in all processes being traced.

To fix this, we reuse the same entry function as when tracing_thresh is not
set and do everything as in the regular case except for writing the function entry
to the ring buffer.

Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>
Signed-off-by: Joel Fernandes <agnel.joel@...il.com>
---
 kernel/trace/trace_functions_graph.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index a663cbb..0967fac 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -337,6 +337,13 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	if (ftrace_graph_notrace_addr(trace->func))
 		return 1;
 
+	/*
+	 * Stop here if tracing_threshold is set. We only write function return
+	 * events to the ring buffer.
+	 */
+	if (tracing_thresh)
+		return 1;
+
 	local_irq_save(flags);
 	cpu = raw_smp_processor_id();
 	data = per_cpu_ptr(tr->trace_buffer.data, cpu);
@@ -354,14 +361,6 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	return ret;
 }
 
-static int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
-{
-	if (tracing_thresh)
-		return 1;
-	else
-		return trace_graph_entry(trace);
-}
-
 static void
 __trace_graph_function(struct trace_array *tr,
 		unsigned long ip, unsigned long flags, int pc)
@@ -456,7 +455,7 @@ static int graph_trace_init(struct trace_array *tr)
 	set_graph_array(tr);
 	if (tracing_thresh)
 		ret = register_ftrace_graph(&trace_graph_thresh_return,
-					    &trace_graph_thresh_entry);
+					    &trace_graph_entry);
 	else
 		ret = register_ftrace_graph(&trace_graph_return,
 					    &trace_graph_entry);
-- 
2.5.0