From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 1/3] ipuv3-crtc: add remove action for devres data Date: Wed, 3 Apr 2019 09:22:10 +0200 Message-ID: <20190403072210.GP2665@phenom.ffwll.local> References: <0687f68004b28ed3a364b06a9eb64e2e@agner.ch> <20190402134904.588-1-m.grzeschik@pengutronix.de> <20190402134904.588-2-m.grzeschik@pengutronix.de> <1554220163.2338.2.camel@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1554220163.2338.2.camel@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: Philipp Zabel Cc: Michael Grzeschik , airlied@linux.ie, gregkh@linuxfoundation.org, kernel@pengutronix.de, rafael@kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux@armlinux.org.uk List-Id: dri-devel@lists.freedesktop.org On Tue, Apr 02, 2019 at 05:49:23PM +0200, Philipp Zabel wrote: > Hi Michael, > > On Tue, 2019-04-02 at 15:49 +0200, Michael Grzeschik wrote: > > The destroy function in drm_mode_config_cleanup will remove the objects > > in ipu-drm-core by calling its destroy functions if the bind function > > fails. The drm_crtc is also part of the devres allocated ipu_crtc > > object. The ipu_crtc object will already be cleaned up if the bind for > > the crtc fails. This leads drm_crtc_cleanup try to clean already freed > > memory. > > > > We fix this issue by adding the devres action ipu_crtc_remove_head which > > will remove its head from the objects in ipu-drm-core which then never > > calls its destroy function anymore. > > > > Signed-off-by: Michael Grzeschik > > --- > > drivers/gpu/drm/imx/ipuv3-crtc.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c > > index ec3602ebbc1cd..fa1ee33a43d77 100644 > > --- a/drivers/gpu/drm/imx/ipuv3-crtc.c > > +++ b/drivers/gpu/drm/imx/ipuv3-crtc.c > > @@ -429,6 +429,14 @@ static int ipu_crtc_init(struct ipu_crtc *ipu_crtc, > > return ret; > > } > > > > +static void ipu_crtc_remove_head(void *data) > > +{ > > + struct ipu_crtc *ipu_crtc = data; > > + struct drm_crtc *crtc = &ipu_crtc->base; > > + > > + list_del(&crtc->head); > > I don't think reaching into drm_crtc internals like this is going to be > robust. Currently, this is either missing the rest of drm_crtc_cleanup, > or it will crash if drm_crtc_init_with_planes hasn't been called yet. > > I think you could call devm_add_action with a function that calls > drm_crtc_cleanup after drm_crtc_init_with_planes in ipu_crtc_init. > > Alternatively, the ipu_crtc allocation could be changed to kzalloc. It > would then have to freed manually in the drm_crtc_funcs->destroy > callback. Dirty secret of devm: You can't use it for any drm_ structure, because the lifetimes of those do not match the lifetimes of the underlying device. We'd need to tie the lifetimes of drm objects to drm_device. Noralf has some patches to move that forward. We'd need something like drm_dev_kzalloc which releases memory when drm_device is freed. Agreed that digging even deeper into the devm deadend is not a good idea. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch