From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH 1/2] drm/i915: Don't drop pinned fences Date: Mon, 27 Jan 2014 21:26:26 +0000 Message-ID: <20140127212626.GE2508@nuc-i3427.alporthouse.com> References: <1390855788-20422-1-git-send-email-daniel.vetter@ffwll.ch> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from fireflyinternet.com (mail.fireflyinternet.com [87.106.93.118]) by gabe.freedesktop.org (Postfix) with ESMTP id 3B134106200 for ; Mon, 27 Jan 2014 13:26:32 -0800 (PST) Content-Disposition: inline In-Reply-To: <1390855788-20422-1-git-send-email-daniel.vetter@ffwll.ch> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Daniel Vetter Cc: Intel Graphics Development List-Id: intel-gfx@lists.freedesktop.org On Mon, Jan 27, 2014 at 09:49:47PM +0100, Daniel Vetter wrote: > Userspace can currently provoke this when e.g. trying to use a pinned > scanout as a cursor or overlay target. Later on that might lead to > some fun fence pin count mayhem. > > Spurred by Ville's report that something goes wrong here and > originally I've thought that this might slip through the pwrite gtt > fastpath. But that one checks of obj tiling, so should be ok. > > But one thing that _does_ blow up is the vma unbinding with more than > one address space. The next patch will fix this. It's buggy behaviour, so if (WARN_ON(fence->pin_count) return -EBUSY; I did worry that we would then have some unexpected failure, a new EBUSY returning to userspace, but I think along the paths that can trigger it, we have already returned EBUSY in the (dim and distant) past. -Chris -- Chris Wilson, Intel Open Source Technology Centre