Re: [PATCH] drm/ttm: Fix race condition in ttm_bo_delayed_delete

From: Francisco Jerez <currojerez-sGOZH3hwPm2sTnJN9+BGXg@public.gmane.org>
To: Luca Barbieri <luca-Ukmtq+NC3rhBHFWNQifrYwC/G2K4zDHf@public.gmane.org>
Cc: "airlied-cv59FeDIM0c@public.gmane.org"
	<airlied-cv59FeDIM0c@public.gmane.org>,
	"nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
	<nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>,
	Thomas Hellstrom
	<thellstrom-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>,
	"dri-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org"
	<dri-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>,
	Thomas Hellstrom <thomas-4+hqylr40dJg9hUCZPvPmw@public.gmane.org>
Subject: Re: [PATCH] drm/ttm: Fix race condition in ttm_bo_delayed_delete
Date: Thu, 21 Jan 2010 18:39:03 +0100	[thread overview]
Message-ID: <87r5pjbbns.fsf@riseup.net> (raw)
In-Reply-To: <ff13bc9a1001210830g2653f672r918f8cb90cbf6170-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> (Luca Barbieri's message of "Thu, 21 Jan 2010 17:30:33 +0100")

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Luca Barbieri <luca-Ukmtq+NC3rhBHFWNQifrYwC/G2K4zDHf@public.gmane.org> writes:

>> The card also keeps some internal FIFO caches, so it seems to me that
>> getting that safe of races and efficient at the same time could be a bit
>> non-trivial.
>
> Are they flushable?
> It seems this *might* do the job:
> if (!pfifo->cache_flush(dev))
> return;
> pfifo->reassign(dev, false);
> pfifo->cache_flush(dev);
> pfifo->cache_pull(dev, false);
>
>
> pfifo->cache_pull(dev, true);
> pfifo->reassign(dev, true);

Yeah, that would probably do the job, but it's likely to be too slow to
be useful.

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