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Subject[PATCH 8/8] ftrace: separate out the function enabled variable
Currently the function tracer uses the global tracer_enabled variable that
is used to keep track if the tracer is enabled or not. The function tracing
startup needs to be separated out, otherwise the internal happenings of
the tracer startup is also recorded.

This patch creates a ftrace_function_enabled variable to all the starting
of the function traces to happen after everything has been started.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
kernel/trace/trace.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
Index: linux-tip.git/kernel/trace/trace.c
===================================================================
--- linux-tip.git.orig/kernel/trace/trace.c 2008-07-10 20:26:33.000000000 -0400
+++ linux-tip.git/kernel/trace/trace.c 2008-07-10 20:38:17.000000000 -0400
@@ -96,6 +96,9 @@ static DEFINE_PER_CPU(struct trace_array
/* tracer_enabled is used to toggle activation of a tracer */
static int tracer_enabled = 1;

+/* function tracing enabled */
+int ftrace_function_enabled;
+
/*
* trace_nr_entries is the number of entries that is allocated
* for a buffer. Note, the number of entries is always rounded
@@ -134,6 +137,7 @@ static notrace void no_trace_init(struct
{
int cpu;

+ ftrace_function_enabled = 0;
if(tr->ctrl)
for_each_online_cpu(cpu)
tracing_reset(tr->data[cpu]);
@@ -985,7 +989,7 @@ function_trace_call(unsigned long ip, un
long disabled;
int cpu;

- if (unlikely(!tracer_enabled))
+ if (unlikely(!ftrace_function_enabled))
return;

if (skip_trace(ip))
@@ -1010,11 +1014,15 @@ static struct ftrace_ops trace_ops __rea

void tracing_start_function_trace(void)
{
+ ftrace_function_enabled = 0;
register_ftrace_function(&trace_ops);
+ if (tracer_enabled)
+ ftrace_function_enabled = 1;
}

void tracing_stop_function_trace(void)
{
+ ftrace_function_enabled = 0;
unregister_ftrace_function(&trace_ops);
}
#endif
@@ -1850,8 +1858,10 @@ __tracing_open(struct inode *inode, stru
m->private = iter;

/* stop the trace while dumping */
- if (iter->tr->ctrl)
+ if (iter->tr->ctrl) {
tracer_enabled = 0;
+ ftrace_function_enabled = 0;
+ }

if (iter->trace && iter->trace->open)
iter->trace->open(iter);
@@ -1884,8 +1894,14 @@ int tracing_release(struct inode *inode,
iter->trace->close(iter);

/* reenable tracing if it was previously enabled */
- if (iter->tr->ctrl)
+ if (iter->tr->ctrl) {
tracer_enabled = 1;
+ /*
+ * It is safe to enable function tracing even if it
+ * isn't used
+ */
+ ftrace_function_enabled = 1;
+ }
mutex_unlock(&trace_types_lock);

seq_release(inode, file);
--


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