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>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b5b25b6..c8a852a 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -912,9 +912,15 @@ void tracing_reset_current(int cpu)
        tracing_reset(&global_trace, cpu);
 }
 
-void tracing_reset_current_online_cpus(void)
+void tracing_reset_all_online_cpus(void)
 {
-       tracing_reset_online_cpus(&global_trace);
+       struct trace_array *tr;
+
+       mutex_lock(&trace_types_lock);
+       list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+               tracing_reset_online_cpus(tr);
+       }
+       mutex_unlock(&trace_types_lock);
 }
 
 #define SAVED_CMDLINES 128

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6728a24..fa60b29 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -496,7 +496,7 @@ int tracing_is_enabled(void);
 void tracing_reset(struct trace_array *tr, int cpu);
 void tracing_reset_online_cpus(struct trace_array *tr);
 void tracing_reset_current(int cpu);
-void tracing_reset_current_online_cpus(void);
+void tracing_reset_all_online_cpus(void);
 int tracing_open_generic(struct inode *inode, struct file *filp);
 struct dentry *trace_create_file(const char *name,
                                 umode_t mode,

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 9a7dc4b..a376ab5 100644 (file)
--- 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,