GEM - radeon cs ioctl deadlock

Ben Skeggs skeggsb at
Wed Oct 13 18:47:19 PDT 2010

On Thu, 2010-10-14 at 08:14 +1000, Dave Airlie wrote:
> On Wed, 2010-10-13 at 17:57 -0400, Jerome Glisse wrote:
> > So we are facing a deadlock with the radeon cs ioctl. When a buffer is given
> > a name (with flink) we could endup with 2 handle pointing to the same
> > object (flink object and open it from same file descriptor). Would it be ok
> > if i change gem open to first look if we already have an handle for the
> > object and to use that handle instead of creating a new one ? Or could
> > this break intel driver ?
> I think r300g worked around this already, maybe we should just avoid
> doing it from userspace if possible.
We had this in nouveau at some point.  In the end, I prevented the
deadlock from occuring by checking that a process doesn't reserve the
same buffer twice (we store file_priv in a reserved_by field in the bo
as we reserve the buffers), and then just fixed userspace.

> Dave.
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