tracing: Simplify test for function_graph tracing start point

In the function graph tracer, a calling function is to be traced
only when it is enabled through the set_graph_function file,
or when it is nested in an enabled function.

Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested
or not. Looking at 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 yet, it is left for future usage.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4B4DB0B6.7040607@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 2 insertions, 6 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f2252296607c..616b135c9eb9 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -215,7 +215,8 @@ 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);
@@ -228,9 +229,6 @@ 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);
@@ -278,8 +276,6 @@ 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);
 }