1 files changed, 48 insertions, 0 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 3bcb9df9334..19332200c45 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -345,11 +345,59 @@ static struct dentry *event_trace_events_dir(void)
         return d_events;
 }
 
+struct event_subsystem {
+        struct list_head        list;
+        const char              *name;
+        struct dentry           *entry;
+};
+
+static LIST_HEAD(event_subsystems);
+
+static struct dentry *
+event_subsystem_dir(const char *name, struct dentry *d_events)
+{
+        struct event_subsystem *system;
+
+        /* First see if we did not already create this dir */
+        list_for_each_entry(system, &event_subsystems, list) {
+                if (strcmp(system->name, name) == 0)
+                        return system->entry;
+        }
+
+        /* need to create new entry */
+        system = kmalloc(sizeof(*system), GFP_KERNEL);
+        if (!system) {
+                pr_warning("No memory to create event subsystem %s\n",
+                           name);
+                return d_events;
+        }
+
+        system->entry = debugfs_create_dir(name, d_events);
+        if (!system->entry) {
+                pr_warning("Could not create event subsystem %s\n",
+                           name);
+                kfree(system);
+                return d_events;
+        }
+
+        system->name = name;
+        list_add(&system->list, &event_subsystems);
+
+        return system->entry;
+}
+
 static int
 event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
 {
         struct dentry *entry;
 
+        /*
+         * If the trace point header did not define TRACE_SYSTEM
+         * then the system would be called "TRACE_SYSTEM".
+         */
+        if (strcmp(call->system, "TRACE_SYSTEM") != 0)
+                d_events = event_subsystem_dir(call->system, d_events);
+
         call->dir = debugfs_create_dir(call->name, d_events);
         if (!call->dir) {
                 pr_warning("Could not create debugfs "