From: Eric Anholt <eric@anholt.net>
To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: "Thomas Hellström" <thomas@shipmail.org>,
DRI <dri-devel@lists.sourceforge.net>,
"Linux Kernel" <linux-kernel@vger.kernel.org>
Subject: Re: Gem GTT mmaps..
Date: Tue, 10 Feb 2009 14:00:01 -0800 [thread overview]
Message-ID: <1234303201.32506.8.camel@gaiman> (raw)
In-Reply-To: <200902061424.02906.jbarnes@virtuousgeek.org>
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On Fri, 2009-02-06 at 14:24 -0800, Jesse Barnes wrote:
> On Friday, February 6, 2009 1:35 pm Thomas Hellström wrote:
> > Jesse Barnes wrote:
> > > 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?
> >
> > Yes, an mmap() is always paired with a vm_close(), and the vm_close()
> > also happens in a crash situation.
>
> This one should cover the cases you found.
> - ref at map time will keep the object around so fault shouldn't fail
> - additional threads will take their refs in vm_open/close
> - unmap will unref and remove mmap_offset allowing object to be freed
sw_finish doesn't mean unmap (note that it doesn't actually unmap).
If you want to actually unmap, that should be done with munmap.
--
Eric Anholt
eric@anholt.net eric.anholt@intel.com
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next prev parent reply other threads:[~2009-02-10 22:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-04 22:32 Gem GTT mmaps Thomas Hellström
2009-02-04 23:02 ` Jesse Barnes
2009-02-04 23:42 ` Eric Anholt
2009-02-05 18:37 ` Jesse Barnes
2009-02-06 17:14 ` Jesse Barnes
2009-02-06 21:35 ` Thomas Hellström
2009-02-06 22:24 ` Jesse Barnes
2009-02-06 22:39 ` Thomas Hellström
2009-02-06 23:22 ` Jesse Barnes
2009-02-07 0:52 ` Chris Wilson
2009-02-11 22:01 ` Jesse Barnes
2009-02-07 8:06 ` Xavier Bestel
2009-02-10 22:00 ` Eric Anholt [this message]
2009-02-10 22:58 ` Jesse Barnes
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