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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 6B248ECE58D for ; Wed, 9 Oct 2019 14:09:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3A7721848 for ; Wed, 9 Oct 2019 14:09:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="YnqCuIIF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729883AbfJIOJS (ORCPT ); Wed, 9 Oct 2019 10:09:18 -0400 Received: from mail-ed1-f68.google.com ([209.85.208.68]:33463 "EHLO mail-ed1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729471AbfJIOJS (ORCPT ); Wed, 9 Oct 2019 10:09:18 -0400 Received: by mail-ed1-f68.google.com with SMTP id c4so2182865edl.0 for ; Wed, 09 Oct 2019 07:09:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=Ggm5FnPBWudwKM7bMG2DlNAhhZbMe/QrjNBGIC21iLE=; b=YnqCuIIF4UjVn4HFsfE/AMYmTYKiPdUIcORH84mX/PlfmNBc/fSAWjPbb+SFtiEaj5 CJwG0TCw8MvXNqBwWvRa5icbOZLDJc9LfzGCi4ILVlt+b596PwwqKJi2If4srCw+yT/J 9iuCxay/yJEpJJgrY0i5Ld8SI7b05zSZ/NLc8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition :content-transfer-encoding:in-reply-to:user-agent; bh=Ggm5FnPBWudwKM7bMG2DlNAhhZbMe/QrjNBGIC21iLE=; b=owRtFezXkjKwGDr21HiHPr8rQ8PtB3TS0y2J+fUMW1Au0xhSFDGpPxmzKPmcSdBm53 V6CKbfyl/DPvmp13W945zxZ3GrxgTxaloeDHGgyIeppeOdTM1Brj1xK67LzvkBsrLLVT iQwtPwVDMY42Keki2vzTwjIeO6SXUEAz/ZCIW3stG3L/Hl97I9jPDbnyybnRp1Lg409Y qsKA8toQyCP+MIIW0nyQohiFomeEsPUsuaJ73U4N0c2sf4zATBOIcdJHnhbJ6ipXdP7y YK2CjX6eJpKWljFBzNYgQtjF8LigX+PTtMmZbjcUYm+NQbnlSukNCoNkTZ4oxkqGL2JW 8FVg== X-Gm-Message-State: APjAAAXV0zG2wNapnlGT5yOsG49Smf/OjQ5JMWnEsED+NjnaMM4AxT6d KGcb+x3sWDthZvapo+Z7IMID4g== X-Google-Smtp-Source: APXvYqzkirb8on6ORe6NpqSckThXHb3Tav3Cj0WPhAo5jbAa/jP+L4b2aIMdTn9K+fFgrnr9a9Um2w== X-Received: by 2002:a17:906:fcac:: with SMTP id qw12mr2982663ejb.31.1570630156129; Wed, 09 Oct 2019 07:09:16 -0700 (PDT) Received: from phenom.ffwll.local (212-51-149-96.fiber7.init7.net. [212.51.149.96]) by smtp.gmail.com with ESMTPSA id t22sm375873edd.79.2019.10.09.07.09.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Oct 2019 07:09:15 -0700 (PDT) Date: Wed, 9 Oct 2019 16:09:12 +0200 From: Daniel Vetter To: christian.koenig@amd.com Cc: Daniel Vetter , dri-devel@lists.freedesktop.org, sumit.semwal@linaro.org, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Subject: Re: [PATCH 2/4] drm/ttm: use the parent resv for ghost objects v2 Message-ID: <20191009140912.GY16989@phenom.ffwll.local> References: <20190829142917.13058-1-christian.koenig@amd.com> <20190829142917.13058-3-christian.koenig@amd.com> <20191008092552.GG16989@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux phenom 5.2.0-2-amd64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Wed, Oct 09, 2019 at 03:10:09PM +0200, Christian König wrote: > Am 08.10.19 um 11:25 schrieb Daniel Vetter: > > On Thu, Aug 29, 2019 at 04:29:15PM +0200, Christian König wrote: > > > This way we can even pipeline imported BO evictions. > > > > > > v2: Limit this to only cases when the parent object uses a separate > > > reservation object as well. This fixes another OOM problem. > > > > > > Signed-off-by: Christian König > > Since I read quite a bit of ttm I figured I'll review this too, but I'm > > totally lost. And git blame gives me at best commits with one-liner commit > > messages, and the docs aren't explaining much at all either (and generally > > they didn't get updated at all with all the changes in the past years). > > > > I have a vague idea of what you're doing here, but not enough to do review > > with any confidence. And from other ttm patches from amd it feels a lot > > like we have essentially a bus factor of 1 for all things ttm :-/ > > Yeah, that's one of a couple of reasons why I want to get rid of TTM in the > long term. > > Basically this is a bug fix for delay freeing ttm objects. When we hang the > ttm object on a ghost object to be freed and the ttm object is an imported > DMA-buf we run into the problem that we want to drop the mapping, but have > the wrong lock taken (the lock of the ghost and not of the parent). Got intrigued, did some more digging, I guess the bugfix part is related to: commit 841e763b40764a7699ae07f4cb1921af62d6316d Author: Christian König Date: Thu Jul 20 20:55:06 2017 +0200 drm/ttm: individualize BO reservation obj when they are freed and that's why you switch everything over to useing _resv instead of the pointer. But then I still don't follow the details ... > > Regards, > Christian. > > > -Daniel > > > > > --- > > > drivers/gpu/drm/ttm/ttm_bo_util.c | 16 +++++++++------- > > > 1 file changed, 9 insertions(+), 7 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c > > > index fe81c565e7ef..2ebe9fe7f6c8 100644 > > > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c > > > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c > > > @@ -517,7 +517,9 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo, > > > kref_init(&fbo->base.kref); > > > fbo->base.destroy = &ttm_transfered_destroy; > > > fbo->base.acc_size = 0; > > > - fbo->base.base.resv = &fbo->base.base._resv; > > > + if (bo->base.resv == &bo->base._resv) > > > + fbo->base.base.resv = &fbo->base.base._resv; I got confused a bit at first, until I spotted the fbo->base = *bo; somewhere above. So I think that part makes sense, together with the above cited patch. I think at least, confidence on this is very low ... > > > + > > > dma_resv_init(fbo->base.base.resv); > > > ret = dma_resv_trylock(fbo->base.base.resv); Shouldn't this be switched over to _resv too? Otherwise feels like unbalanced locking. > > > WARN_ON(!ret); > > > @@ -716,7 +718,7 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo, > > > if (ret) > > > return ret; > > > - dma_resv_add_excl_fence(ghost_obj->base.resv, fence); > > > + dma_resv_add_excl_fence(&ghost_obj->base._resv, fence); > > > /** > > > * If we're not moving to fixed memory, the TTM object > > > @@ -729,7 +731,7 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo, > > > else > > > bo->ttm = NULL; > > > - ttm_bo_unreserve(ghost_obj); > > > + dma_resv_unlock(&ghost_obj->base._resv); > > > ttm_bo_put(ghost_obj); > > > } > > > @@ -772,7 +774,7 @@ int ttm_bo_pipeline_move(struct ttm_buffer_object *bo, > > > if (ret) > > > return ret; > > > - dma_resv_add_excl_fence(ghost_obj->base.resv, fence); > > > + dma_resv_add_excl_fence(&ghost_obj->base._resv, fence); > > > /** > > > * If we're not moving to fixed memory, the TTM object > > > @@ -785,7 +787,7 @@ int ttm_bo_pipeline_move(struct ttm_buffer_object *bo, > > > else > > > bo->ttm = NULL; > > > - ttm_bo_unreserve(ghost_obj); > > > + dma_resv_unlock(&ghost_obj->base._resv); I guess dropping the lru part here (aside from switching from ->resv to ->_resv, which is your bugfix I think) doesn't matter since the ghost object got all cleared up and isn't on any lists anyway? Otoh how does it work then ... Not clear to me why this is safe. > > > ttm_bo_put(ghost_obj); > > > } else if (from->flags & TTM_MEMTYPE_FLAG_FIXED) { > > > @@ -841,7 +843,7 @@ int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo) > > > if (ret) > > > return ret; > > > - ret = dma_resv_copy_fences(ghost->base.resv, bo->base.resv); > > > + ret = dma_resv_copy_fences(&ghost->base._resv, bo->base.resv); > > > /* Last resort, wait for the BO to be idle when we are OOM */ > > > if (ret) > > > ttm_bo_wait(bo, false, false); > > > @@ -850,7 +852,7 @@ int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo) > > > bo->mem.mem_type = TTM_PL_SYSTEM; > > > bo->ttm = NULL; > > > - ttm_bo_unreserve(ghost); > > > + dma_resv_unlock(&ghost->base._resv); > > > ttm_bo_put(ghost); > > > return 0; > > > -- > > > 2.17.1 -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch