linux-kernel - Re: Gem GTT mmaps..

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Date:	Fri, 6 Feb 2009 09:14:59 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Eric Anholt <eric@...olt.net>
Cc:	Thomas Hellström <thomas@...pmail.org>,
	DRI <dri-devel@...ts.sourceforge.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Gem GTT mmaps..

On Thursday, February 5, 2009 10:37 am Jesse Barnes wrote:
> So if we leave the lookup reference around from the GTT mapping ioctl, that
> would take care of new mappings.  And if we added/removed references at VM
> open/close time, we should be covered for fork.  But is it ok to add a new
> unref in the finish ioctl for GTT mapped objects?  I don't think so,
> because we don't know for sure if the caller was the one that created the
> new fake offset (which would be one way of detecting whether it was GTT
> mapped). Seems like we need a new unmap ioctl?  Or we could put the mapping
> ref/unref in libdrm, where it would be tracked on a per-process basis...

Ah but maybe we should just tear down the fake offset at unmap time; then we'd 
be able to use it as an existence test for the mapping and get the 
refcounting right.  The last thing I thought of was whether we'd be ok in a 
map_gtt -> crash case.  I *think* the vm_close code will deal with that, if 
we do a deref there?

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center
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