On 13/01/2020 10:44, Chris Wilson wrote:
> Since commit 422d7df4f090 ("drm/i915: Replace engine->timeline with a
> plain list"), we used the default embedded priotree slot for the virtual
> engine request queue, which means we can also use the same solitary slot
> with the scheduler. However, the priolist is expected to be guarded by
> the engine->active.lock, but this is not true for the virtual engine
>
> References: 422d7df4f090 ("drm/i915: Replace engine->timeline with a plain
> list")
> Signed-off-by: Chris Wilson <[email protected]>
> Cc: Mika Kuoppala <[email protected]>
> Cc: Tvrtko Ursulin <[email protected]>
> ---
> drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++
> drivers/gpu/drm/i915/i915_request.c | 4 +++-
> drivers/gpu/drm/i915/i915_request.h | 16 ++++++++++++++++
> drivers/gpu/drm/i915/i915_scheduler.c | 3 +--
> 4 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c
> b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index a6ac37dece0a..685659f079a2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -985,6 +985,8 @@ __unwind_incomplete_requests(struct intel_engine_cs
> *engine)
>
> GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
>
> list_move(&rq->sched.link, pl);
> + set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> +
> active = rq;
> } else {
> struct intel_engine_cs *owner = rq->context->engine;
> @@ -2473,6 +2475,7 @@ static void execlists_submit_request(struct
> i915_request *request)
> spin_lock_irqsave(&engine->active.lock, flags);
>
> queue_request(engine, &request->sched, rq_prio(request));
> + set_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags);
Move into queue_request so it is closer to priolist management, just like at
other call sites?
Also, these are all under the engine active lock so non-atomic set/clear could
be used, no?
>
> GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
> GEM_BUG_ON(list_empty(&request->sched.link));
> diff --git a/drivers/gpu/drm/i915/i915_request.c
> b/drivers/gpu/drm/i915/i915_request.c
> index be185886e4fc..9ed0d3bc7249 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -408,8 +408,10 @@ bool __i915_request_submit(struct i915_request *request)
> xfer: /* We may be recursing from the signal callback of another i915
> fence */
> spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
>
> - if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags))
> + if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)) {
> list_move_tail(&request->sched.link, &engine->active.requests);
> + clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags);
> + }
>
> if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) &&
> !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags) &&
> diff --git a/drivers/gpu/drm/i915/i915_request.h
> b/drivers/gpu/drm/i915/i915_request.h
> index 031433691a06..f3e50ec989b8 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -70,6 +70,17 @@ enum {
> */
> I915_FENCE_FLAG_ACTIVE = DMA_FENCE_FLAG_USER_BITS,
>
> + /*
> + * I915_FENCE_FLAG_PQUEUE - this request is ready for execution
> + *
> + * Using the scheduler, when a request is ready for execution it is put
> + * into the priority queue. We want to track its membership within that
> + * queue so that we can easily check before rescheduling.
> + *
> + * See i915_request_in_priority_queue()
> + */
> + I915_FENCE_FLAG_PQUEUE,
> +
> /*
> * I915_FENCE_FLAG_SIGNAL - this request is currently on signal_list
> *
> @@ -361,6 +372,11 @@ static inline bool i915_request_is_active(const struct
> i915_request *rq)
> return test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags);
> }
>
> +static inline bool i915_request_in_priority_queue(const struct i915_request
> *rq)
> +{
> + return test_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> +}
> +
> /**
> * Returns true if seq1 is later than seq2.
> */
> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c
> b/drivers/gpu/drm/i915/i915_scheduler.c
> index bf87c70bfdd9..4f6e4d6c590a 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler.c
> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
> @@ -338,8 +338,7 @@ static void __i915_schedule(struct i915_sched_node *node,
> continue;
> }
>
> - if (!intel_engine_is_virtual(engine) &&
> - !i915_request_is_active(node_to_request(node))) {
> + if (i915_request_in_priority_queue(node_to_request(node))) {
Not shown in this diff before this if block we have:
if (list_empty(&node->link)) {
/*
* If the request is not in the priolist queue because
* it is not yet runnable, then it doesn't contribute
* to our preemption decisions. On the other hand,
* if the request is on the HW, it too is not in the
* queue; but in that case we may still need to reorder
* the inflight requests.
*/
continue;
}
What is the difference between list_empty(&node->link) and
!i915_request_in_priority_queue?
Regards,
Tvrtko
> if (!cache.priolist)
> cache.priolist =
> i915_sched_lookup_priolist(engine,
>
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