4 files changed, 15 insertions, 3 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a102b11eacf2..1281969103b8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -620,7 +620,12 @@ static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
 static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
 static int cmdline_idx;
 static DEFINE_SPINLOCK(trace_cmdline_lock);
-atomic_t trace_record_cmdline_disabled;
+
+/* trace in all context switches */
+atomic_t trace_record_cmdline_enabled __read_mostly;
+
+/* temporary disable recording */
+atomic_t trace_record_cmdline_disabled __read_mostly;
 
 static void trace_init_cmdlines(void)
 {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 21c29ee13e53..8991c5efcc74 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -216,6 +216,8 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
 extern unsigned long tracing_max_latency;
 extern unsigned long tracing_thresh;
 
+extern atomic_t trace_record_cmdline_enabled;
+
 void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu);
 void update_max_tr_single(struct trace_array *tr,
                           struct task_struct *tsk, int cpu);
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 4165d34bd28a..0a084656d7cf 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -29,12 +29,14 @@ static void function_reset(struct trace_array *tr)
 static void start_function_trace(struct trace_array *tr)
 {
         function_reset(tr);
+        atomic_inc(&trace_record_cmdline_enabled);
         tracing_start_function_trace();
 }
 
 static void stop_function_trace(struct trace_array *tr)
 {
         tracing_stop_function_trace();
+        atomic_dec(&trace_record_cmdline_enabled);
 }
 
 static void function_trace_init(struct trace_array *tr)
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 5671db0e1827..a3376478fc2c 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -29,8 +29,6 @@ ctx_switch_func(void *__rq, struct task_struct *prev, struct task_struct *next)
         if (!tracer_enabled)
                 return;
 
-        tracing_record_cmdline(prev);
-
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
         data = tr->data[cpu];
@@ -73,6 +71,9 @@ void
 ftrace_ctx_switch(void *__rq, struct task_struct *prev,
                   struct task_struct *next)
 {
+        if (unlikely(atomic_read(&trace_record_cmdline_enabled)))
+                tracing_record_cmdline(prev);
+
         /*
          * If tracer_switch_func only points to the local
          * switch func, it still needs the ptr passed to it.
@@ -134,11 +135,13 @@ static void sched_switch_reset(struct trace_array *tr)
 static void start_sched_trace(struct trace_array *tr)
 {
         sched_switch_reset(tr);
+        atomic_inc(&trace_record_cmdline_enabled);
         tracer_enabled = 1;
 }
 
 static void stop_sched_trace(struct trace_array *tr)
 {
+        atomic_dec(&trace_record_cmdline_enabled);
         tracer_enabled = 0;
 }