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Subject[PATCH v2 35/40] tracing: Reverse the order event_mutex/trace_types_lock are taken
Date
Change the order event_mutex and trace_types_lock are taken, to avoid
circular dependencies and lockdep spew.

Changing the order shouldn't matter to any current code, but does to
anything that takes the event_mutex first and then trace_types_lock.
This is the case when calling tracing_set_clock from inside an event
command, which already holds the event_mutex.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
kernel/trace/trace_events.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c93540c..889802c 100644
--- 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 @@ void trace_event_eval_update(struct trace_eval_map **map, int len)
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;
}
--
1.9.3
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