Commit 218d372c authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
Browse files

fgraph: Keep track of when fgraph_ops are registered or not 

Add a warning if unregister_ftrace_graph() is called without ever
registering it, or if register_ftrace_graph() is called twice. This can
detect errors when they happen and not later when there's a side effect:

Link: https://lore.kernel.org/all/20250617120830.24fbdd62@gandalf.local.home/

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/20250701194451.22e34724@gandalf.local.home


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 437889b9

kernel/trace/fgraph.c

+13 −3
Original line number Diff line number Diff line
@@ -1325,6 +1325,10 @@ int register_ftrace_graph(struct fgraph_ops *gops) 
	int ret = 0;

	int i = -1;



	if (WARN_ONCE(gops->ops.flags & FTRACE_OPS_FL_GRAPH,

		      "function graph ops registered again"))

		return -EBUSY;



	guard(mutex)(&ftrace_lock);



	if (!fgraph_stack_cachep) {
@@ -1401,17 +1405,21 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) 
{

	int command = 0;



	if (WARN_ONCE(!(gops->ops.flags & FTRACE_OPS_FL_GRAPH),

		      "function graph ops unregistered without registering"))

		return;



	guard(mutex)(&ftrace_lock);



	if (unlikely(!ftrace_graph_active))

		return;

		goto out;



	if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE ||

		     fgraph_array[gops->idx] != gops))

		return;

		goto out;



	if (fgraph_lru_release_index(gops->idx) < 0)

		return;

		goto out;



	fgraph_array[gops->idx] = &fgraph_stub;
@@ -1434,4 +1442,6 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) 
		unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);

	}

	gops->saved_func = NULL;

 out:

	gops->ops.flags &= ~FTRACE_OPS_FL_GRAPH;

}