Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> In a simple test case that writes to scratch and then busy-waits for the
> batch to be signaled, we observe that the signal is before the write is
> posted. That is bad news.
>
> Splitting the flush + write_dword into two separate flush_dw prevents
> the issue from being reproduced, we can presume the post-sync op is not
> so post-sync.
>
Only thing that is mildly surpricing is that first one doesnt
need postop write.
> Testcase: igt/gem_exec_fence/parallel
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_lrc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index d0be98b67138..a437140a987d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -5047,7 +5047,8 @@ gen12_emit_fini_breadcrumb_tail(struct i915_request *request, u32 *cs)
>
> static u32 *gen12_emit_fini_breadcrumb(struct i915_request *rq, u32 *cs)
> {
> - return gen12_emit_fini_breadcrumb_tail(rq, emit_xcs_breadcrumb(rq, cs));
> + cs = emit_xcs_breadcrumb(rq, __gen8_emit_flush_dw(cs, 0, 0, 0));
> + return gen12_emit_fini_breadcrumb_tail(rq, cs);
> }
>
> static u32 *
> --
> 2.20.1
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