On Tue, 5 Sep 2017 16:57:47 -0500 Tom Zanussi <[email protected]> wrote:
> 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. This is a very scary patch. I'll apply it and run a bunch of tests with lockdep enabled. Let's see what blows up (or not). -- Steve > > Signed-off-by: Tom Zanussi <[email protected]> > --- > 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; > }
