linux-kernel - [PATCH] tracing, function_graph: simplify test for tracing

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Date:	Wed, 13 Jan 2010 19:38:30 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] tracing, function_graph: simplify test for tracing


For function_graph, a calling function is to be traced only when
it is enabled or it is nested in a enabled function.

Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested or not.
read the code, we can get this:
(trace->depth > 0) <==> (TSK_TRACE_FL_GRAPH is set)

trace->depth is more explicit to tell that it is nested.
So we use trace->depth directly and simplify the code.

No functionality is changed.
TSK_TRACE_FL_GRAPH is not removed now, it is left for future usage.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 3976520..9a69b9c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -506,7 +506,7 @@ static inline int ftrace_graph_addr(unsigned long addr)
 {
 	int i;
 
-	if (!ftrace_graph_count || test_tsk_trace_graph(current))
+	if (!ftrace_graph_count)
 		return 1;
 
 	for (i = 0; i < ftrace_graph_count; i++) {
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b1342c5..8e17a57 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -218,7 +218,8 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	if (!ftrace_trace_task(current))
 		return 0;
 
-	if (!ftrace_graph_addr(trace->func))
+	/* trace it when it is-nested-in or is a function enabled. */
+	if (!(trace->depth || ftrace_graph_addr(trace->func)))
 		return 0;
 
 	local_irq_save(flags);
@@ -231,9 +232,6 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	} else {
 		ret = 0;
 	}
-	/* Only do the atomic if it is not already set */
-	if (!test_tsk_trace_graph(current))
-		set_tsk_trace_graph(current);
 
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
@@ -281,8 +279,6 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
 		pc = preempt_count();
 		__trace_graph_return(tr, trace, flags, pc);
 	}
-	if (!trace->depth)
-		clear_tsk_trace_graph(current);
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
 }

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