linux-kernel - [PATCH] tracing: tprobe-events: Fix to clean up tprobe correctly when module unload

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Message-ID:  <174124210422.3014222.12363751066695445786.stgit@mhiramat.tok.corp.google.com>
Date: Thu,  6 Mar 2025 15:21:44 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH] tracing: tprobe-events: Fix to clean up tprobe correctly when module unload

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

When unloading module, the tprobe events are not correctly cleaned
up. Thus it becomes `fprobe-event` and never be enabled again even
if loading the same module again.

For example;

 # cd /sys/kernel/tracing
 # modprobe trace_events_sample
 # echo 't:my_tprobe foo_bar' >> dynamic_events
 # cat dynamic_events
t:tracepoints/my_tprobe foo_bar
 # rmmod trace_events_sample
 # cat dynamic_events
f:tracepoints/my_tprobe foo_bar

As you can see, the second time my_tprobe starts with 'f' instead
of 't'.

This cleans up (unregister) the tprobe events when module is
unloaded.

Fixes: 57a7e6de9e30 ("tracing/fprobe: Support raw tracepoints on future loaded modules")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/trace/trace_fprobe.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index e27305d31fc5..d5fc0c5bf879 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -775,7 +775,7 @@ static void __unregister_trace_fprobe(struct trace_fprobe *tf)
 		if (trace_fprobe_is_tracepoint(tf)) {
 			tracepoint_probe_unregister(tf->tpoint,
 					tf->tpoint->probestub, NULL);
-			tf->tpoint = NULL;
+			tf->tpoint = TRACEPOINT_STUB;
 			tf->mod = NULL;
 		}
 	}
@@ -1007,12 +1007,8 @@ static int __tracepoint_probe_module_cb(struct notifier_block *self,
 				    trace_probe_is_enabled(&tf->tp))
 					reenable_trace_fprobe(tf);
 			}
-		} else if (val == MODULE_STATE_GOING && tp_mod->mod == tf->mod) {
-			tracepoint_probe_unregister(tf->tpoint,
-					tf->tpoint->probestub, NULL);
-			tf->tpoint = NULL;
-			tf->mod = NULL;
-		}
+		} else if (val == MODULE_STATE_GOING && tp_mod->mod == tf->mod)
+			__unregister_trace_fprobe(tf);
 	}
 	mutex_unlock(&event_mutex);