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authorFrederic Weisbecker <fweisbec@gmail.com>2010-01-14 08:23:15 +0100
committerIngo Molnar <mingo@elte.hu>2010-01-17 08:06:25 +0100
commit24a53652e361321b09df5040711e69387344ce09 (patch)
tree9db320478f5233ee4b427292cc57ad4b3a66fefb /kernel/trace/trace_functions_graph.c
parentd931369b74b3d6f2044f595af6f3dd074f65d9cf (diff)
downloadop-kernel-dev-24a53652e361321b09df5040711e69387344ce09.zip
op-kernel-dev-24a53652e361321b09df5040711e69387344ce09.tar.gz
tracing: Drop the tr check from the graph tracing path
Each time we save a function entry from the function graph tracer, we check if the trace array is set, which is wasteful because it is set anyway before we start the tracer. All we need is to ensure we have good read and write orderings. When we set the trace array, we just need to guarantee it to be visible before starting tracing. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> LKML-Reference: <1263453795-7496-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace_functions_graph.c')
-rw-r--r--kernel/trace/trace_functions_graph.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b1342c5..f225229 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -212,9 +212,6 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
int cpu;
int pc;
- if (unlikely(!tr))
- return 0;
-
if (!ftrace_trace_task(current))
return 0;
@@ -287,11 +284,20 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
local_irq_restore(flags);
}
+void set_graph_array(struct trace_array *tr)
+{
+ graph_array = tr;
+
+ /* Make graph_array visible before we start tracing */
+
+ smp_mb();
+}
+
static int graph_trace_init(struct trace_array *tr)
{
int ret;
- graph_array = tr;
+ set_graph_array(tr);
ret = register_ftrace_graph(&trace_graph_return,
&trace_graph_entry);
if (ret)
@@ -301,11 +307,6 @@ static int graph_trace_init(struct trace_array *tr)
return 0;
}
-void set_graph_array(struct trace_array *tr)
-{
- graph_array = tr;
-}
-
static void graph_trace_reset(struct trace_array *tr)
{
tracing_stop_cmdline_record();
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