[Mesa-dev] [PATCH v6.2] egl: Allow creation of per surface out fence

Fri Sep 8 17:33:08 UTC 2017

On 8 September 2017 at 17:54, Rafael Antognolli
<rafael.antognolli at intel.com> wrote:
> On Fri, Sep 08, 2017 at 08:32:05AM -0700, Marathe, Yogesh wrote:
>> > -----Original Message-----
>> > From: Emil Velikov [mailto:emil.l.velikov at gmail.com]
>> > Sent: Friday, September 8, 2017 8:28 PM
>> > To: Marathe, Yogesh <yogesh.marathe at intel.com>
>> > Cc: Tomasz Figa <tfiga at chromium.org>; Antognolli, Rafael
>> > <rafael.antognolli at intel.com>; Janes, Mark A <mark.a.janes at intel.com>;
>> > mesa-dev at lists.freedesktop.org; Gao, Shuo <shuo.gao at intel.com>; Liu,
>> > Zhiquan <zhiquan.liu at intel.com>; daniels at collabora.com;
>> > nicolai.haehnle at amd.com; eric at engestrom.ch; Wu, Zhongmin
>> > <zhongmin.wu at intel.com>; kenneth at whitecape.org; Kondapally, Kalyan
>> > <kalyan.kondapally at intel.com>; fernetmenta at online.de;
>> > tarceri at itsqueeze.com; varad.gautam at collabora.com
>> > Subject: Re: [Mesa-dev] [PATCH v6.2] egl: Allow creation of per surface out
>> > fence
>> >
>> > On 8 September 2017 at 14:47, Marathe, Yogesh <yogesh.marathe at intel.com>
>> > wrote:
>> > > Hello Folks,
>> > >
>> > > Sorry for late reply, I took quite some time to CTS up, comments below.
>> > >
>> > >> -----Original Message-----
>> > >> From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org] On
>> > >> Behalf Of Marathe, Yogesh
>> > >> Sent: Friday, September 1, 2017 10:16 AM
>> > >> To: Tomasz Figa <tfiga at chromium.org>
>> > >> Cc: Gao, Shuo <shuo.gao at intel.com>; Liu, Zhiquan
>> > >> <zhiquan.liu at intel.com>; daniels at collabora.com;
>> > >> nicolai.haehnle at amd.com; Antognolli, Rafael
>> > >> <rafael.antognolli at intel.com>; eric at engestrom.ch; Emil Velikov
>> > >> <emil.l.velikov at gmail.com>; Wu, Zhongmin <zhongmin.wu at intel.com>;
>> > >> kenneth at whitecape.org; Kondapally, Kalyan
>> > >> <kalyan.kondapally at intel.com>; fernetmenta at online.de;
>> > >> mesa-dev at lists.freedesktop.org; tarceri at itsqueeze.com;
>> > >> varad.gautam at collabora.com
>> > >> Subject: Re: [Mesa-dev] [PATCH v6.2] egl: Allow creation of per
>> > >> surface out fence
>> > >>
>> > >> Tomasz,
>> > >>
>> > >> > -----Original Message-----
>> > >> > From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org] On
>> > >> > Behalf Of Tomasz Figa
>> > >> > Sent: Friday, September 1, 2017 9:53 AM
>> > >> > To: Marathe, Yogesh <yogesh.marathe at intel.com> On Thu, Aug 31, 2017
>> > >> > at 2:18 AM, Marathe, Yogesh <yogesh.marathe at intel.com> wrote:
>> > >> > >> -----Original Message-----
>> > >> > >> From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org]
>> > >> > >> On Behalf Of Emil Velikov
>> > >> > >> Sent: Wednesday, August 30, 2017 9:44 PM
>> > >> > >> To: Marathe, Yogesh <yogesh.marathe at intel.com>
>> > >> > >> Cc: Gao, Shuo <shuo.gao at intel.com>; Liu, Zhiquan
>> > >> > >> <zhiquan.liu at intel.com>; daniels at collabora.com;
>> > >> > >> nicolai.haehnle at amd.com; Antognolli, Rafael
>> > >> > >> <rafael.antognolli at intel.com>; eric at engestrom.ch; Wu, Zhongmin
>> > >> > >> <zhongmin.wu at intel.com>; tfiga at chromium.org;
>> > >> kenneth at whitecape.org;
>> > >> > >> Kondapally, Kalyan <kalyan.kondapally at intel.com>;
>> > >> > >> fernetmenta at online.de; mesa-dev at lists.freedesktop.org;
>> > >> > >> tarceri at itsqueeze.com; varad.gautam at collabora.com
>> > >> > >> Subject: Re: [Mesa-dev] [PATCH v6.2] egl: Allow creation of per
>> > >> > >> surface out fence
>> > >> > >>
>> > >> > >> On 30 August 2017 at 15:39, Marathe, Yogesh
>> > >> > >> <yogesh.marathe at intel.com>
>> > >> > >> wrote:
>> > >> > >>
>> > >> > >> >
>> > >> > >> > Thank you, Tomasz and all involved for the help and guidance.
>> > >> > >> >
>> > >> > >> Our excitement was short lived - see commit
>> > >> > >> 8c9df0daf20206fafb7df77b1edcbc41b8e91372.
>> > >> > >>
>> > >> > >> Seems the patch was not run through the Intel CI, though I'm
>> > >> > >> should not have assumed that you're aware of if.
>> > >> > >> Please get in touch with Mark Janes (Cc'd here, janesma on IRC).
>> > >> > >> He can set you up and/or run a branch for you.
>> > >> > >>
>> > >> > >
>> > >> > > No problem. I will contact Mark.
>> > >> > >
>> > >> > > Primarily looks like platform / kernel version issue.
>> > >> > > intel_get_boolean() for I915_PARAM_HAS_EXEC_FENCE is false, but I
>> > >> > > see following in i915_drv.c:915_getparam in kernel, no clue why
>> > >> > > that would come false in UMD.
>> > >> > >
>> > >> > > ...
>> > >> > >         case I915_PARAM_HAS_EXEC_FENCE:
>> > >> > >                 /* For the time being all of these are always true;
>> > >> > >                  * if some supported hardware does not have one of these
>> > >> > >                  * features this value needs to be provided from
>> > >> > >                  * INTEL_INFO(), a feature macro, or similar.
>> > >> > >                  */
>> > >> > >                 value = 1;
>> > >> > >                 break;
>> > >> > > ...
>> > >> >
>> > >> > Which kernel are you looking at? Remember that not everyone uses
>> > >> > current upstream master. There is a number of upstream stable
>> > >> > releases and downstream forks. Grepping for
>> > >> > I915_PARAM_HAS_EXEC_FENCE on http://elixir.free-electrons.com, shows
>> > that it was only added in Linux 4.12.
>> > >> >
>> > >>
>> > >> I'm on 4.9.x but I see my kernel  tree has following patch, so this
>> > >> looks like it is done for android (cherry picked / backport). That’s why it
>> > worked for me always!
>> > >>
>> > >> commit f0683754f03fa308a2657cb1dadbf235c9607188
>> > >> Author: Chris Wilson <chris at chris-wilson.co.uk>
>> > >> Date:   Fri Jan 27 09:40:08 2017 +0000
>> > >>
>> > >>     drm/i915: Support explicit fencing for execbuf
>> > >>
>> > >> Nonetheless, as you mentioned, I've synced up with Mark and we've
>> > >> created a separate branch where CTS / intel mesa CI can run. Let me try to fix
>> > this.
>> > >>
>> > >> Caveat: To have flatland running on android  there was another issue
>> > >> in kernel which needed a fix. Details -
>> > >> https://bugs.freedesktop.org/show_bug.cgi?id=101656
>> > >
>> > > I was able to run CTS (https://github.com/KhronosGroup/VK-GL-CTS) on
>> > > this patch for x11_egl. I see exact same results before and after patch on
>> > Ubuntu 16.04 setup.
>> > > Mark had also mentioned  this works fine on 4.12 onwards (essentially with
>> > drm/i915:
>> > > Support explicit fencing for execbuf patch in kernel).
>> > >
>> > > Regarding the primary reason why this was reverted
>> > >
>> > > mesa/drivers/dri/i965/brw_sync.c:491: brw_dri_create_fence_fd:
>> > > Assertion `brw->screen->has_exec_fence' failed.
>> > >
>> > > This assertion evident on older kernels. Although I'm bit surprised
>> > > here after looking at the code. Older kernels where this explicit
>> > > fencing is not supported must've returned 'false' for has_exec_fence in
>> > intelInitScreen2().
>> > >
>> > >    screen->has_exec_fence =
>> > >      intel_get_boolean(screen, I915_PARAM_HAS_EXEC_FENCE);
>> > >
>> > > It appears that’s coming 'true' and due to that we set
>> > > enable_out_fence in dri2_init_surface() (based on get_capabilities()) which
>> > causes create_fence_fd call on non-supported kernels.
>> > > Isn't this strange? Can someone please comment?
>> > >
>> > In all fairness there was a few wtf moments as Mark mentioned the issue. As on
>> > a quick look "it cannot happen" :-\
>> >
>> > One way is to add some printfs "debugging" across the board and check with
>> > Mark if he can run (only?) the affected test on the CI.
>> >
>>
>> Number of tests failing on CI due to this are huge, any 'one' can be picked up. I do have
>> my CI branch setup now but I don’t think I can use it for debugging (not advised).  I'll sync
>> up with Mark again. Just wanted a confirmation, I'm not missing something obvious. Thanks.
>
> Hi Yogesh,
>
> I replied to you already when you messaged in private, the error is not
> related to the kernel returning true for that, it's related to a memory
> corruption caused by wrong use of the dri2_surf_init inside
> platform_x11_dri3.c. Quoting myself:
>
> "More specifically, it looks like this test fails every time:
>
> glcts -n dEQP-EGL.functional.query_context.get_current_context.rgb888_window
>
> I see several valgrind warnings inside platform_x11_dri3.c. I believe you are
> probably accessing the dri2_surf before it was allocated, or after it was
> freed..."
>
> When I tested this back then, the "out_fence_enable" (or whatever was called)
> in dri2 was false, but after a couple runs it would become a bogus number,
> which also points to memory corruption.
>
> I suggest ignoring the kernel and focusing on valgrind debugging.
>
Nicely spotted there Rafael.

The issue is that the dri3 surface primitive wraps around _EGLSurface.
Thus as we reference the new variables we effectively write onto the
loader_dri3 bits. And at a later stage the dri3 loader code toggles
those to "use out fence = true".

-Emil