1 files changed, 19 insertions, 3 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f8fdb9cedc24..2e37857f7dfe 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -96,6 +96,9 @@ static DEFINE_PER_CPU(struct trace_array_cpu, max_data);
 /* 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 trace_array *tr)
 {
         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, unsigned long parent_ip)
         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 __read_mostly =
 
 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, struct file *file, int *ret)
                 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, struct file *file)
                 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);