linux-kernel - Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence implementation for fences

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Date:	Wed, 23 Jul 2014 11:30:44 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	Christian König <christian.koenig@....com>
Cc:	Christian König <deathsimple@...afone.de>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Thomas Hellstrom <thellstrom@...are.com>,
	nouveau <nouveau@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Ben Skeggs <bskeggs@...hat.com>,
	"Deucher, Alexander" <alexander.deucher@....com>
Subject: Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence
 implementation for fences

On Wed, Jul 23, 2014 at 11:27 AM, Christian König
<christian.koenig@....com> wrote:
> You submit a job to the hardware and then block the job to wait for radeon
> to be finished? Well than this would indeed require a hardware reset, but
> wouldn't that make the whole problem even worse?
>
> I mean currently we block one userspace process to wait for other hardware
> to be finished with a buffer, but what you are describing here blocks the
> whole hardware to wait for other hardware which in the end blocks all
> userspace process accessing the hardware.

There is nothing new here with prime - if one context hangs the gpu it
blocks everyone else on i915.

> Talking about alternative approaches wouldn't it be simpler to just offload
> the waiting to a different kernel or userspace thread?

Well this is exactly what we'll do once we have the scheduler. But
this is an orthogonal issue imo.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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