From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73B97C77B6F for ; Thu, 13 Apr 2023 12:43:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229894AbjDMMn5 (ORCPT ); Thu, 13 Apr 2023 08:43:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229722AbjDMMn4 (ORCPT ); Thu, 13 Apr 2023 08:43:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16E9893D1 for ; Thu, 13 Apr 2023 05:43:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A9E476146C for ; Thu, 13 Apr 2023 12:43:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 629DDC433D2; Thu, 13 Apr 2023 12:43:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1681389834; bh=yOCVEPTkqmwzrbgaO4trLtk8j+cugrX7CunNTUSAF4o=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=eo/swswdEMkWLuTPtC+XSfNe7DxDo2uPvkry0F0awj0Xy5GYN62lRckycHDCOCMu7 xTfmUHC881NkN6xEPSTxJs6G5rwPTk/OUcFxbKzYP8kJyp0q6BJrFAjtE0YVg52dGa l93ocDixpnNZVssYz3IIvocuBFfTq0t72K+VZEeibMLvktwDqj3HLCz/2iA+6z3HW4 MyiaNaKS4VNCyx0+U8BzxmodHPMZM8Tf0Vnee8zXIaaAPUUcYamTPCurR1YXn2X/Wc JUiXEaMgYxyt1j25oDps/VYxBPIEa4XhDa1xKZFX4xJMaXtguQe0XbjNSael1HYD+u ONyEslOtsuPag== Message-ID: Subject: Re: [PATCH] drm: make drm_dp_add_payload_part2 gracefully handle NULL state pointer From: Jeff Layton To: Jani Nikula , David Airlie , Daniel Vetter Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Harry Wentland , Alex Deucher Date: Thu, 13 Apr 2023 08:43:52 -0400 In-Reply-To: <87edooarpq.fsf@intel.com> References: <20230413111254.22458-1-jlayton@kernel.org> <87edooarpq.fsf@intel.com> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2023-04-13 at 15:31 +0300, Jani Nikula wrote: > On Thu, 13 Apr 2023, Jeff Layton wrote: > > I've been experiencing some intermittent crashes down in the display > > driver code. The symptoms are ususally a line like this in dmesg: > >=20 > > amdgpu 0000:30:00.0: [drm] Failed to create MST payload for port 00= 0000006d3a3885: -5 > >=20 > > ...followed by an Oops due to a NULL pointer dereference. > >=20 > > The real bug is probably in the caller of this function, which is > > passing it a NULL state pointer, but this patch at least keeps my > > machine from oopsing when this occurs. >=20 > My fear is that papering over this makes the root cause harder to find. >=20 > Cc: Harry, Alex >=20 >=20 > BR, > Jani. >=20 >=20 I'm happy to help track down the root cause. Display drivers are somewhat outside my wheelhouse though. Maybe we can throw a WARNING when this happens? I'd just like it to not crash my machine. > >=20 > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D2184855 > > Signed-off-by: Jeff Layton > > --- > > drivers/gpu/drm/display/drm_dp_mst_topology.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > >=20 > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gp= u/drm/display/drm_dp_mst_topology.c > > index 38dab76ae69e..87ad406c50f9 100644 > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c > > @@ -3404,7 +3404,8 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_to= pology_mgr *mgr, > > =20 > > /* Skip failed payloads */ > > if (payload->vc_start_slot =3D=3D -1) { > > - drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, s= kipping part 2\n", > > + drm_dbg_kms(state ? state->dev : NULL, > > + "Part 1 of payload creation for %s failed, skipping part 2\n", > > payload->port->connector->name); > > return -EIO; > > } >=20 --=20 Jeff Layton