[Intel-gfx] [PATCH v6 3/7] drm/i915: Add per context timelines to fence object

Chris Wilson chris at chris-wilson.co.uk
Thu Feb 18 14:49:49 UTC 2016

On Thu, Feb 18, 2016 at 02:24:06PM +0000, John.C.Harrison at Intel.com wrote:
> From: John Harrison <John.C.Harrison at Intel.com>
> The fence object used inside the request structure requires a sequence
> number. Although this is not used by the i915 driver itself, it could
> potentially be used by non-i915 code if the fence is passed outside of
> the driver. This is the intention as it allows external kernel drivers
> and user applications to wait on batch buffer completion
> asynchronously via the dma-buff fence API.
> To ensure that such external users are not confused by strange things
> happening with the seqno, this patch adds in a per context timeline
> that can provide a guaranteed in-order seqno value for the fence. This
> is safe because the scheduler will not re-order batch buffers within a
> context - they are considered to be mutually dependent.

This is still nonsense. Just implement per-context seqno.

Chris Wilson, Intel Open Source Technology Centre

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