* H. Nikolaus Schaller <h...@goldelico.com> [180618 18:33]: > >> So code just needs group cleanup on failed probing and fixing the mutex > >> around pinctrl_generic_add_group(). > >> > >> I think we need the mutex because a race still can happen when > >> create_pinctrl() is calling pcs_dt_node_to_map() > >> and pinctrl_generic_add_group() w/o being locked on pinctrl_maps_mutex. > >> > >> The race I suspect is that two drivers are trying to insert the same name > >> and may come > >> both to the conclusion that it does not yet exist. And both insert into > >> the radix tree. > >> > >> The window of risk is small though... It is in pinctrl_generic_add_group() > >> between calling > >> pinctrl_generic_group_name_to_selector() and radix_tree_insert() so we > >> probably won't > >> see it in real hardware tests. > > > > Hmm but that race should be already fixed with mutex held > > by the pin controller drivers with these fixes? Or am I > > missing something still? > > Hm. Maybe we refer to a different mutex?
Yes I think that's the case, you're talking about a different mutex here :) > I had seen the call sequence > > create_pinctrl()-> pinctrl_dt_to_map() -> pcs_dt_node_to_map() -> > pinctrl_generic_add_group() > > w/o any lock inside. > > There is a mutex_lock(&pinctrl_maps_mutex); in create_pinctrl(), but locked > after that. > > Or is there a lock outside of create_pinctrl()? > > If I look into the stack dumps, call nesting is > > driver_probe_device() -> pinctrl_bind_pins() -> devm_pinctrl_get() -> > create_pinctrl() > > They all do no locking. > > Maybe I am missing something. Can you please post a patch for that as you already have it debugged? That's easier to understand than reading a verbal patch :) Regards, Tony
