From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gustavo Padovan Subject: Re: [RFC 1/8] dma-buf/fence: add fence_collection fences Date: Wed, 18 May 2016 11:30:11 -0300 Message-ID: <20160518143011.GA2287@joana> References: <1460683781-22535-1-git-send-email-gustavo@padovan.org> <1460683781-22535-2-git-send-email-gustavo@padovan.org> <20160415080254.GQ2510@phenom.ffwll.local> <5710AE61.9040308@amd.com> <20160415182750.GA23954@joana> <20160415192550.GZ2510@phenom.ffwll.local> <573C14C3.8080604@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <573C14C3.8080604@amd.com> Sender: linux-kernel-owner@vger.kernel.org To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Gustavo Padovan , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Daniel Stone , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Riley Andrews , Rob Clark , Greg Hackmann , John Harrison , laurent.pinchart@ideasonboard.com, seanpaul@google.com, marcheu@google.com, m.chehab@samsung.com, Maarten Lankhorst List-Id: dri-devel@lists.freedesktop.org Hi Christian, 2016-05-18 Christian K=F6nig : > Am 15.04.2016 um 21:25 schrieb Daniel Vetter: > > On Fri, Apr 15, 2016 at 11:27:50AM -0700, Gustavo Padovan wrote: > > > 2016-04-15 Christian K=F6nig : > > > > Amdgpu also has an implementation for a fence collection which = uses a a > > > > hashtable to keep the fences grouped by context (e.g. only the = latest fence > > > > is keept for each context). See amdgpu_sync.c for reference. > > > >=20 > > > > We should either make the collection similar in a way that you = can add as > > > > many fences as you want (like the amdgpu implementation) or mak= e it static > > > > and only add a fixed number of fences right from the beginning. > > > >=20 > > > > I can certainly see use cases for both, but if you want to stic= k with a > > > > static approach you should probably call the new object fence_a= rray instead > > > > of fence_collection and do as Daniel suggested. > > > Maybe we can go for something in between. Have fence_collection_i= nit() > > > need at least two fences to create the fence_collection. Then > > > fence_collection_add() would add more dinamically. > > The problem with adding fences later on is that it makes it trivial= to add > > deadlocks and loops. Just add the fence collection to itself, boom.= From > > that pov it's an unsafe api, and hence something to avoid. > > -Daniel >=20 > Any conclusion on this? Did any version of the patch made it upstream= ? >=20 > I'm in the need of an array based fence collection right now as well.= Any > objection that I just take the patch proposed here and fix the commen= ts or > are you still else working on this right now? I have a new version of this patch that I didn't send upstream yet because it is part of a bigger patchset. But I can split it and send what I have for fence_collection later today. Gustavo