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=-14.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 C6F44C48BDF for ; Sat, 19 Jun 2021 03:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 984AF6135F for ; Sat, 19 Jun 2021 03:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235621AbhFSDMt (ORCPT ); Fri, 18 Jun 2021 23:12:49 -0400 Received: from m12-17.163.com ([220.181.12.17]:37227 "EHLO m12-17.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235206AbhFSDMq (ORCPT ); Fri, 18 Jun 2021 23:12:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=TRcSN 7ER03UoZDCumjMkss4Yzc53jQuAXejLACVSkss=; b=nQvxERUu8wJNHjX7R7Ckj hfio2mJu3gHffs3LB0oGnAuo8LkS4YPOrahHw1mjmWvSosMVO4rOjIz2krfN+AwO fYYE7+LqMbQniSNusFZWuhkv4Niq/NFLg7wLSe3KoJKBGLc+iwDXKwF2UrAMfGW4 IPz5HyA1qU6FHtqwYvszyM= Received: from localhost (unknown [218.17.89.111]) by smtp13 (Coremail) with SMTP id EcCowABXtDjjX81geZOD8Q--.57668S2; Sat, 19 Jun 2021 11:09:24 +0800 (CST) Date: Sat, 19 Jun 2021 11:09:23 +0800 From: Chunyou Tang To: Steven Price Cc: robh@kernel.org, tomeu.vizoso@collabora.com, alyssa.rosenzweig@collabora.com, airlied@linux.ie, daniel@ffwll.ch, ChunyouTang , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] drm/panfrost:modify 'break' to 'continue' to traverse the circulation Message-ID: <20210619110923.00001c64@163.com> In-Reply-To: <4d289eed-59f2-161a-40d1-2a434a1955c2@arm.com> References: <20210617080414.1940-1-tangchunyou@163.com> <4d289eed-59f2-161a-40d1-2a434a1955c2@arm.com> Organization: icube X-Mailer: Claws Mail 3.10.1 (GTK+ 2.16.6; i586-pc-mingw32msvc) MIME-Version: 1.0 Content-Type: text/plain; charset=GB18030 Content-Transfer-Encoding: 8bit X-CM-TRANSID: EcCowABXtDjjX81geZOD8Q--.57668S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxCrWUXF17AFWDGF48ZF47Arb_yoW5CrWxpF WUCr15AFWkX3Wrta929a4xCF4jq34Fqry5uF98AwsxArsxtF1YvF409a4rWr9rAF45KF4U twsrWa47W3y0yw7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jDR6rUUUUU= X-Originating-IP: [218.17.89.111] X-CM-SenderInfo: 5wdqwu5kxq50rx6rljoofrz/xtbBRRO1UVPAMiD73gACsU Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, 1, from https://lore.kernel.org/lkml/31644881-134a-2d6e-dddf-e658a3a8176b@arm.com/ I can see what your sent,I used a wrong email address,Now it correct. 2, > >Unless I'm mistaken the situation where some mappings may be NULL is > >caused by the loop in panfrost_lookup_bos() not completing > >successfully > >(panfrost_gem_mapping_get() returning NULL). In this case if > >mappings[i] > >is NULL then all following mappings must also be NULL. So 'break' > >allows > >us to skip the later ones. Admittedly the performance here isn't > >important so I'm not sure it's worth the optimisation, but AIUI this > >code isn't actually wrong. from panfrost_lookup_bos(),you can see: for (i = 0; i < job->bo_count; i++) { struct panfrost_gem_mapping *mapping; bo = to_panfrost_bo(job->bos[i]); ICUBE_DEBUG_PRINTK("panfrost bo gem handle=0x%x is_dumb=%d\n", bo->gem_handle, bo->is_dumb); if (!bo->is_dumb) { mapping = panfrost_gem_mapping_get(bo, priv); if (!mapping) { ret = -EINVAL; break; } atomic_inc(&bo->gpu_usecount); job->mappings[i] = mapping; } else { atomic_inc(&bo->gpu_usecount); job->mappings[i] = NULL; } } if bo->is_dumb is TRUE,the job->mappings[i] will set to NULL,and the while will be continue,so if job->mappings[i] is NULL,the following can not be NULL. 3, I've had this problem in our project,the value of is_dumb like these: 0 0 0 1 0 0 0 so,when job->mappings[i] is NULL,we can not break the while in panfrost_job_cleanup(). thanks Chunyou ÓÚ Fri, 18 Jun 2021 13:43:25 +0100 Steven Price дµÀ: > On 17/06/2021 09:04, ChunyouTang wrote: > > From: ChunyouTang > > > > The 'break' can cause 'Memory manager not clean during takedown' > > > > It cannot use break to finish the circulation,it should use > > > > continue to traverse the circulation.it should put every mapping > > > > which is not NULL. > > You don't appear to have answered my question about whether you've > actually seen this happen (and ideally what circumstances). In my > previous email[1] I explained why I don't think this is needed. You > need to convince me that I've overlooked something. > > Thanks, > > Steve > > [1] > https://lore.kernel.org/r/31644881-134a-2d6e-dddf-e658a3a8176b%40arm.com > > > Signed-off-by: ChunyouTang > > --- > > drivers/gpu/drm/panfrost/panfrost_job.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c > > b/drivers/gpu/drm/panfrost/panfrost_job.c index > > 6003cfeb1322..52bccc1d2d42 100644 --- > > a/drivers/gpu/drm/panfrost/panfrost_job.c +++ > > b/drivers/gpu/drm/panfrost/panfrost_job.c @@ -281,7 +281,7 @@ > > static void panfrost_job_cleanup(struct kref *ref) if > > (job->mappings) { for (i = 0; i < job->bo_count; i++) { > > if (!job->mappings[i]) > > - break; > > + continue; > > > > atomic_dec(&job->mappings[i]->obj->gpu_usecount); > > panfrost_gem_mapping_put(job->mappings[i]); > >