From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [Letux-kernel] BUG: drivers/pinctrl/core: races in pinctrl_groups and deferred probing Date: Mon, 18 Jun 2018 21:34:08 -0700 Message-ID: <20180619043408.GT112168@atomide.com> References: <4DE2E482-B0D3-4799-9E2D-74E2180B305B@goldelico.com> <20180618091433.GP112168@atomide.com> <20180618095428.GQ112168@atomide.com> <20180618115122.GT26255@atomide.com> <20180618181744.GS112168@atomide.com> <404C63D9-169E-4051-88E0-2856F3602A72@goldelico.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <404C63D9-169E-4051-88E0-2856F3602A72@goldelico.com> Sender: linux-kernel-owner@vger.kernel.org To: "H. Nikolaus Schaller" Cc: Christ van Willegen , Linus Walleij , Linux Kernel Mailing List , "open list:GPIO SUBSYSTEM" , Andy Shevchenko , kernel@pyra-handheld.com, Discussions about the Letux Kernel List-Id: linux-gpio@vger.kernel.org * H. Nikolaus Schaller [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