function_graph: Remove the use of FTRACE_NOTRACE_DEPTH

The curr_ret_stack is no longer set to a negative value when a function is
not to be traced by the function graph tracer. Remove the usage of
FTRACE_NOTRACE_DEPTH, as it is no longer needed.
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -790,7 +790,6 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
  */
 #define __notrace_funcgraph		notrace
 
-#define FTRACE_NOTRACE_DEPTH 65536
 #define FTRACE_RETFUNC_DEPTH 50
 #define FTRACE_RETSTACK_ALLOC_SIZE 32
 extern int register_ftrace_graph(trace_func_graph_ret_t retfunc,

kernel/trace/fgraph.c

@@ -112,16 +112,6 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
 
 	index = current->curr_ret_stack;
 
-	/*
-	 * A negative index here means that it's just returned from a
-	 * notrace'd function.  Recover index to get an original
-	 * return address.  See ftrace_push_return_trace().
-	 *
-	 * TODO: Need to check whether the stack gets corrupted.
-	 */
-	if (index < 0)
-		index += FTRACE_NOTRACE_DEPTH;
-
 	if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
 		ftrace_graph_stop();
 		WARN_ON(1);
@@ -190,15 +180,6 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 	 */
 	barrier();
 	current->curr_ret_stack--;
-	/*
-	 * The curr_ret_stack can be less than -1 only if it was
-	 * filtered out and it's about to return from the function.
-	 * Recover the index and continue to trace normal functions.
-	 */
-	if (current->curr_ret_stack < -1) {
-		current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
-		return ret;
-	}
 
 	if (unlikely(!ret)) {
 		ftrace_graph_stop();

kernel/trace/trace_functions_graph.c

@@ -115,9 +115,6 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
 	if (ret != (unsigned long)return_to_handler)
 		return ret;
 
-	if (index < -1)
-		index += FTRACE_NOTRACE_DEPTH;
-
 	if (index < 0)
 		return ret;
 
@@ -675,10 +672,6 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 
 		cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 
-		/* If a graph tracer ignored set_graph_notrace */
-		if (call->depth < -1)
-			call->depth += FTRACE_NOTRACE_DEPTH;
-
 		/*
 		 * Comments display at + 1 to depth. Since
 		 * this is a leaf function, keep the comments
@@ -721,10 +714,6 @@ print_graph_entry_nested(struct trace_iterator *iter,
 		struct fgraph_cpu_data *cpu_data;
 		int cpu = iter->cpu;
 
-		/* If a graph tracer ignored set_graph_notrace */
-		if (call->depth < -1)
-			call->depth += FTRACE_NOTRACE_DEPTH;
-
 		cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 		cpu_data->depth = call->depth;