From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758231AbcG0Ubv (ORCPT ); Wed, 27 Jul 2016 16:31:51 -0400 Received: from mail-yw0-f193.google.com ([209.85.161.193]:35019 "EHLO mail-yw0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752018AbcG0Ubs (ORCPT ); Wed, 27 Jul 2016 16:31:48 -0400 MIME-Version: 1.0 In-Reply-To: <1468856499-19246-1-git-send-email-cpaul@redhat.com> References: <1468856499-19246-1-git-send-email-cpaul@redhat.com> From: Alex Deucher Date: Wed, 27 Jul 2016 16:31:46 -0400 Message-ID: Subject: Re: [PATCH v2] drm/amdgpu: Disable RPM helpers while reprobing connectors on resume To: Lyude Cc: amd-gfx list , "for 3.8" , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , David Airlie , Chunming Zhou , Jammy Zhou , Monk Liu , Flora Cui , Tom St Denis , "open list:RADEON and AMDGPU DRM DRIVERS" , open list Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 18, 2016 at 11:41 AM, Lyude wrote: > Just about all of amdgpu's connector probing functions try to acquire > runtime PM refs. If we try to do this in the context of > amdgpu_resume_kms by calling drm_helper_hpd_irq_event(), we end up > deadlocking the system. > > Since we're guaranteed to be holding the spinlock for RPM in > amdgpu_resume_kms, and we already know the GPU is in working order, we > need to prevent the RPM helpers from trying to run during the initial > connector reprobe on resume. > > There's a couple of solutions I've explored for fixing this, but this > one by far seems to be the simplest and most reliable (plus I'm pretty > sure that's what disable_depth is there for anyway). > > Reproduction recipe: > - Get any laptop dual GPUs using PRIME > - Make sure runtime PM is enabled for amdgpu > - Boot the machine > - If the machine managed to boot without hanging, switch out of X to > another VT. This should definitely cause X to hang infinitely. > > Changes since v1: > - add appropriate #ifdef checks for CONFIG_PM. This is not very > useful, but it appears some kernel test suites test compiling amdgpu > with CONFIG_PM disabled, which results in this patch breaking the builds > if we don't include this #ifdef > > Cc: stable@vger.kernel.org > Cc: Alex Deucher > Signed-off-by: Lyude Applied. Thanks! Alex > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > index 6e92008..b7f5650 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > @@ -1841,7 +1841,23 @@ int amdgpu_resume_kms(struct drm_device *dev, bool resume, bool fbcon) > } > > drm_kms_helper_poll_enable(dev); > + > + /* > + * Most of the connector probing functions try to acquire runtime pm > + * refs to ensure that the GPU is powered on when connector polling is > + * performed. Since we're calling this from a runtime PM callback, > + * trying to acquire rpm refs will cause us to deadlock. > + * > + * Since we're guaranteed to be holding the rpm lock, it's safe to > + * temporarily disable the rpm helpers so this doesn't deadlock us. > + */ > +#ifdef CONFIG_PM > + dev->dev->power.disable_depth++; > +#endif > drm_helper_hpd_irq_event(dev); > +#ifdef CONFIG_PM > + dev->dev->power.disable_depth--; > +#endif > > if (fbcon) { > amdgpu_fbdev_set_suspend(adev, 0); > -- > 2.7.4 >