3 files changed, 54 insertions, 0 deletions

diff --git a/kernel/trace/events.c b/kernel/trace/events.c
index 46e27ad2487e..4e4e45860c58 100644
--- a/kernel/trace/events.c
+++ b/kernel/trace/events.c
@@ -2,6 +2,10 @@
  * This is the place to register all trace points as events.
  */
 
+/* someday this needs to go in a generic header */
+#define __STR(x) #x
+#define STR(x) __STR(x)
+
 #include <trace/trace_events.h>
 
 #include "trace_events.h"
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 3bcb9df93342..19332200c457 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 "
diff --git a/kernel/trace/trace_events.h b/kernel/trace/trace_events.h
index deb95e5006c8..b015d7b19878 100644
--- a/kernel/trace/trace_events.h
+++ b/kernel/trace/trace_events.h
@@ -7,6 +7,7 @@
 
 struct ftrace_event_call {
         char            *name;
+        char            *system;
         struct dentry   *dir;
         int             enabled;
         int             (*regfunc)(void);
@@ -44,6 +45,7 @@ static struct ftrace_event_call __used					\
 __attribute__((__aligned__(4)))                                         \
 __attribute__((section("_ftrace_events"))) event_##call = {             \
         .name                   = #call,                                \
+        .system                 = STR(TRACE_SYSTEM),                    \
         .regfunc                = ftrace_reg_event_##call,              \
         .unregfunc              = ftrace_unreg_event_##call,            \
 }