tracing: Reverse the order of trace_types_lock and event_mutex

In order to make future changes where we need to call
tracing_set_clock() from within an event command, the order of
trace_types_lock and event_mutex must be reversed, as the event command
will hold event_mutex and the trace_types_lock is taken from within
tracing_set_clock().

Link: http://lkml.kernel.org/r/20170921162249.0dde3dca@gandalf.local.home
Requested-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 752e5daf0896fc529876f8801a95e23118713338..5f1ac7d3402ce225933f9d1fbfb41496fac53e6f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7687,6 +7687,7 @@ static int instance_mkdir(const char *name)
        struct trace_array *tr;
        int ret;
 
+       mutex_lock(&event_mutex);
        mutex_lock(&trace_types_lock);
 
        ret = -EEXIST;
@@ -7742,6 +7743,7 @@ static int instance_mkdir(const char *name)
        list_add(&tr->list, &ftrace_trace_arrays);
 
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        return 0;
 
@@ -7753,6 +7755,7 @@ static int instance_mkdir(const char *name)
 
  out_unlock:
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        return ret;
 
@@ -7765,6 +7768,7 @@ static int instance_rmdir(const char *name)
        int ret;
        int i;
 
+       mutex_lock(&event_mutex);
        mutex_lock(&trace_types_lock);
 
        ret = -ENODEV;
@@ -7810,6 +7814,7 @@ static int instance_rmdir(const char *name)
 
  out_unlock:
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        return ret;
 }

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 87468398b9ed6206722db4126cc6c6318580e357..ec0f9aa4e1516bd7fe2ee17b6b12ff27a81d1482 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1406,8 +1406,8 @@ static int subsystem_open(struct inode *inode, struct file *filp)
                return -ENODEV;
 
        /* Make sure the system still exists */
-       mutex_lock(&trace_types_lock);
        mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
        list_for_each_entry(tr, &ftrace_trace_arrays, list) {
                list_for_each_entry(dir, &tr->systems, list) {
                        if (dir == inode->i_private) {
@@ -1421,8 +1421,8 @@ static int subsystem_open(struct inode *inode, struct file *filp)
                }
        }
  exit_loop:
-       mutex_unlock(&event_mutex);
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        if (!system)
                return -ENODEV;
@@ -2294,15 +2294,15 @@ static void __add_event_to_tracers(struct trace_event_call *call);
 int trace_add_event_call(struct trace_event_call *call)
 {
        int ret;
-       mutex_lock(&trace_types_lock);
        mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
 
        ret = __register_event(call, NULL);
        if (ret >= 0)
                __add_event_to_tracers(call);
 
-       mutex_unlock(&event_mutex);
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
        return ret;
 }
 
@@ -2356,13 +2356,13 @@ int trace_remove_event_call(struct trace_event_call *call)
 {
        int ret;
 
-       mutex_lock(&trace_types_lock);
        mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
        down_write(&trace_event_sem);
        ret = probe_remove_event_call(call);
        up_write(&trace_event_sem);
-       mutex_unlock(&event_mutex);
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        return ret;
 }
@@ -2424,8 +2424,8 @@ static int trace_module_notify(struct notifier_block *self,
 {
        struct module *mod = data;
 
-       mutex_lock(&trace_types_lock);
        mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
        switch (val) {
        case MODULE_STATE_COMING:
                trace_module_add_events(mod);
@@ -2434,8 +2434,8 @@ static int trace_module_notify(struct notifier_block *self,
                trace_module_remove_events(mod);
                break;
        }
-       mutex_unlock(&event_mutex);
        mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
 
        return 0;
 }
@@ -2950,24 +2950,24 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
  * creates the event hierachry in the @parent/events directory.
  *
  * Returns 0 on success.
+ *
+ * Must be called with event_mutex held.
  */
 int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr)
 {
        int ret;
 
-       mutex_lock(&event_mutex);
+       lockdep_assert_held(&event_mutex);
 
        ret = create_event_toplevel_files(parent, tr);
        if (ret)
-               goto out_unlock;
+               goto out;
 
        down_write(&trace_event_sem);
        __trace_add_event_dirs(tr);
        up_write(&trace_event_sem);
 
- out_unlock:
-       mutex_unlock(&event_mutex);
-
+ out:
        return ret;
 }
 
@@ -2996,9 +2996,10 @@ early_event_add_tracer(struct dentry *parent, struct trace_array *tr)
        return ret;
 }
 
+/* Must be called with event_mutex held */
 int event_trace_del_tracer(struct trace_array *tr)
 {
-       mutex_lock(&event_mutex);
+       lockdep_assert_held(&event_mutex);
 
        /* Disable any event triggers and associated soft-disabled events */
        clear_event_triggers(tr);
@@ -3019,8 +3020,6 @@ int event_trace_del_tracer(struct trace_array *tr)
 
        tr->event_dir = NULL;
 
-       mutex_unlock(&event_mutex);
-
        return 0;
 }