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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 417EDC4360F for ; Thu, 4 Apr 2019 12:38:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 140822075E for ; Thu, 4 Apr 2019 12:38:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729538AbfDDMin (ORCPT ); Thu, 4 Apr 2019 08:38:43 -0400 Received: from relay11.mail.gandi.net ([217.70.178.231]:36411 "EHLO relay11.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726790AbfDDMin (ORCPT ); Thu, 4 Apr 2019 08:38:43 -0400 Received: from aptenodytes (aaubervilliers-681-1-89-125.w90-88.abo.wanadoo.fr [90.88.30.125]) (Authenticated sender: paul.kocialkowski@bootlin.com) by relay11.mail.gandi.net (Postfix) with ESMTPSA id AF92110004D; Thu, 4 Apr 2019 12:38:38 +0000 (UTC) Message-ID: <23336c399cd31738750fa060854f5a076b722300.camel@bootlin.com> Subject: Re: [PATCH v4 4/4] drm/vc4: Allocate binner bo when starting to use the V3D From: Paul Kocialkowski To: Eric Anholt , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: David Airlie , Daniel Vetter , Thomas Petazzoni , Maxime Ripard , Eben Upton , Daniel Stone Date: Thu, 04 Apr 2019 14:38:38 +0200 In-Reply-To: <87ftqyor88.fsf@anholt.net> References: <20190403154856.9470-1-paul.kocialkowski@bootlin.com> <20190403154856.9470-5-paul.kocialkowski@bootlin.com> <87ftqyor88.fsf@anholt.net> Organization: Bootlin Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Le mercredi 03 avril 2019 à 11:53 -0700, Eric Anholt a écrit : > Paul Kocialkowski writes: > > > The binner bo is not required until the V3D is in use, so avoid > > allocating it at probe and do it on the first non-dumb BO allocation. > > Keep track of which clients are using the V3D and liberate the buffer > > when there is none left. > > > > We also want to keep it alive during runtime suspend/resume to avoid > > failing to allocate it at resume. This happens when the CMA pool is > > full at that point and results in a hard crash. > > > > Signed-off-by: Paul Kocialkowski > > --- > > drivers/gpu/drm/vc4/vc4_bo.c | 32 ++++++++++++++++++++++++++++++++ > > drivers/gpu/drm/vc4/vc4_drv.c | 9 +++++++++ > > drivers/gpu/drm/vc4/vc4_drv.h | 4 ++++ > > drivers/gpu/drm/vc4/vc4_v3d.c | 13 ------------- > > 4 files changed, 45 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c > > index 88ebd681d7eb..b941f09b9378 100644 > > --- a/drivers/gpu/drm/vc4/vc4_bo.c > > +++ b/drivers/gpu/drm/vc4/vc4_bo.c > > @@ -799,6 +799,30 @@ vc4_prime_import_sg_table(struct drm_device *dev, > > return obj; > > } > > > > +static int vc4_prepare_bin_bo(struct drm_device *dev, > > + struct drm_file *file_priv) > > +{ > > + struct vc4_file *vc4file = file_priv->driver_priv; > > + struct vc4_dev *vc4 = to_vc4_dev(dev); > > + int ret; > > + > > + if (!vc4->v3d) > > + return -ENODEV; > > + > > + if (!vc4file->needs_bin_bo) { > > + atomic_inc(&vc4->bin_bo_usecnt); > > + vc4file->needs_bin_bo = true; > > + } > > + > > + if (!vc4->bin_bo) { > > + ret = vc4_v3d_allocate_bin_bo(vc4); > > + if (ret) > > + return ret; > > + } > > + > > This atomic usage looks really racy. For example, multiple clients > could call allocate at the same time and leak one. Or this timeline: > > us them > dec count to 0 > inc count > check bin_bo > free bin_bo Oh, you're definitely right. Sorry I missed that. > vc4_v3d_allocate_bin_bo should probably be a vc4_v3d_bin_bo_get() > returning a kref on the BO, called under a lock protecting both one > file_priv being dereferenced by multiple threads in the kernel at the > same time (so file_priv doesn't try to double-get its ref) and multiple > file_privs trying to get the bin_bo at once. Sounds good, I'll look into it and spin up a new revision soon. Cheers, Paul -- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com