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

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Message-ID: <53CE74B5.3000201@canonical.com>
Date:	Tue, 22 Jul 2014 16:27:01 +0200
From:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
To:	Christian König <christian.koenig@....com>,
	Christian König <deathsimple@...afone.de>,
	Dave Airlie <airlied@...il.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: [PATCH 09/17] drm/radeon: use common fence implementation for
 fences

op 22-07-14 16:24, Christian König schreef:
>> No, you really shouldn't be doing much in the check anyway, it's meant to be a lightweight check. If you're not ready yet because of a lockup simply return not signaled yet.
> It's not only the lockup case from radeon I have in mind here. For userspace queues it might be necessary to call copy_from_user to figure out if a fence is signaled or not.
>
> Returning false all the time is probably not a good idea either.
Having userspace implement a fence sounds like an awful idea, why would you want to do that?

A fence could be exported to userspace, but that would only mean it can wait for it to be signaled with an interface like poll..

~Maarten

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