Re: [PATCH] drm/i915/execlists: Prevent merging requests with conflicting flags

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On 09/10/2019 12:28, Chris Wilson wrote:
We set out-of-bound parameters inside the i915_requests.flags field,
such as disabling preemption or marking the end-of-context. We should
not coalesce consecutive requests if they have differing instructions
as we only inspect the last active request in a context. Thus if we
allow a later request to be merged into the same execution context, it
will mask any of the earlier flags.

References: 2a98f4e65bba ("drm/i915: add infrastructure to hold off preemption on a request")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>


Oops, I missed your patch :(

I guess this works too, potentially providing better timeslicing than the update I made.

I'll give it a go later, but it sounds like it should work.


Thanks,


-Lionel


---
  drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 6db762c509b8..2e5192a9e796 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1233,6 +1233,9 @@ static bool can_merge_rq(const struct i915_request *prev,
  	if (i915_request_completed(next))
  		return true;
+ if (unlikely(prev->flags ^ next->flags))
+		return false;
+
  	if (!can_merge_ctx(prev->hw_context, next->hw_context))
  		return false;


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