tracing: Clear all trace buffers when unloaded module event was used

Currently we do not know what buffer a module event was enabled in.
On unload, it is safest to clear all buffer instances, not just the
top level buffer.

Todo: Clear only the buffer that the event was used in. The
infrastructure is there to do this, but it makes the code a bit
more complex. Lets get the current code vetted before we add that.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 9a7dc4bf1171c..a376ab5eec5cb 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1649,14 +1649,18 @@ static void trace_module_remove_events(struct module *mod)
 		list_del(&file_ops->list);
 		kfree(file_ops);
 	}
+	up_write(&trace_event_mutex);
 
 	/*
 	 * It is safest to reset the ring buffer if the module being unloaded
-	 * registered any events that were used.
+	 * registered any events that were used. The only worry is if
+	 * a new module gets loaded, and takes on the same id as the events
+	 * of this module. When printing out the buffer, traced events left
+	 * over from this module may be passed to the new module events and
+	 * unexpected results may occur.
 	 */
 	if (clear_trace)
-		tracing_reset_current_online_cpus();
-	up_write(&trace_event_mutex);
+		tracing_reset_all_online_cpus();
 }
 
 static int trace_module_notify(struct notifier_block *self,