fgraph: Fix thresh_return clear per-task notrace

When tracing_thresh is enabled, function graph tracing uses
trace_graph_thresh_return() as the return handler. Unlike
trace_graph_return(), it did not clear the per-task TRACE_GRAPH_NOTRACE
flag set by the entry handler for set_graph_notrace addresses. This could
leave the task permanently in "notrace" state and effectively disable
function graph tracing for that task.

Mirror trace_graph_return()'s per-task notrace handling by clearing
TRACE_GRAPH_NOTRACE and returning early when set.

Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Fixes: b842148 ("function_graph: Move graph notrace bit to shadow stack global var")
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Shengming Hu <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: HSM6236

kernel/trace/trace_functions_graph.c

@@ -400,14 +400,15 @@ static void trace_graph_thresh_return(struct ftrace_graph_ret *trace,
 				      struct fgraph_ops *gops,
 				      struct ftrace_regs *fregs)
 {
+	unsigned long *task_var = fgraph_get_task_var(gops);
 	struct fgraph_times *ftimes;
 	struct trace_array *tr;
 	int size;
 
 	ftrace_graph_addr_finish(gops, trace);
 
-	if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
-		trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
+	if (*task_var & TRACE_GRAPH_NOTRACE) {
+		*task_var &= ~TRACE_GRAPH_NOTRACE;
 		return;
 	}