tracing/function-graph-tracer: append the tracing_graph_flag

Impact: Provide a way to pause the function graph tracer

As suggested by Steven Rostedt, the previous patch that prevented from
spinlock function tracing shouldn't use the raw_spinlock to fix it.
It's much better to follow lockdep with normal spinlock, so this patch
adds a new flag for each task to make the function graph tracer able
to be paused. We also can send an ftrace_printk whithout worrying of
the irrelevant traced spinlock during insertion.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 449fa8e9e34f..11cac81eed08 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -401,6 +401,16 @@ static inline int task_curr_ret_stack(struct task_struct *t)
 {
         return t->curr_ret_stack;
 }
+
+static inline void pause_graph_tracing(void)
+{
+        atomic_inc(&current->tracing_graph_pause);
+}
+
+static inline void unpause_graph_tracing(void)
+{
+        atomic_dec(&current->tracing_graph_pause);
+}
 #else
 
 #define __notrace_funcgraph
@@ -412,6 +422,9 @@ static inline int task_curr_ret_stack(struct task_struct *tsk)
 {
         return -1;
 }
+
+static inline void pause_graph_tracing(void) { }
+static inline void unpause_graph_tracing(void) { }
 #endif
 
 #ifdef CONFIG_TRACING
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4c152e0acc9e..4b81fc5f7731 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1379,6 +1379,8 @@ struct task_struct {
          * because of depth overrun.
          */
         atomic_t trace_overrun;
+        /* Pause for the tracing */
+        atomic_t tracing_graph_pause;
 #endif
 #ifdef CONFIG_TRACING
         /* state flags for use by tracers */