Chris Wilson <ch...@chris-wilson.co.uk> writes:

> Now that we have split out the seqno-barrier from the
> engine->get_seqno() callback itself, we can move the users of the
> seqno-barrier to the required callsites simplifying the common code and
> making the required workaround handling much more explicit.
>
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c  |  4 ++--
>  drivers/gpu/drm/i915/i915_drv.h      | 17 ++++++++---------
>  drivers/gpu/drm/i915/i915_gem.c      | 24 ++++++++++++++++--------
>  drivers/gpu/drm/i915/intel_display.c |  2 +-
>  drivers/gpu/drm/i915/intel_pm.c      |  4 ++--
>  5 files changed, 29 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
> b/drivers/gpu/drm/i915/i915_debugfs.c
> index 1499e2337e5d..d09e48455dcb 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -601,7 +601,7 @@ static int i915_gem_pageflip_info(struct seq_file *m, 
> void *data)
>                                          
> i915_gem_request_get_seqno(work->flip_queued_req),
>                                          dev_priv->next_seqno,
>                                          ring->get_seqno(ring),
> -                                        
> i915_gem_request_completed(work->flip_queued_req, true));
> +                                        
> i915_gem_request_completed(work->flip_queued_req));
>                       } else
>                               seq_printf(m, "Flip not associated with any 
> ring\n");
>                       seq_printf(m, "Flip queued on frame %d, (was ready on 
> frame %d), now %d\n",
> @@ -1354,8 +1354,8 @@ static int i915_hangcheck_info(struct seq_file *m, void 
> *unused)
>       intel_runtime_pm_get(dev_priv);
>  
>       for_each_ring(ring, dev_priv, i) {
> -             seqno[i] = ring->get_seqno(ring);
>               acthd[i] = intel_ring_get_active_head(ring);
> +             seqno[i] = ring->get_seqno(ring);

Oh! Perhaps I am overly optimistic but did you just show how to solve
the 'hangcheck elapsed <random> ring idle..' coherency issue
in hangcheck?

I would like to have a separate patch that does this ordering
in here and also in i915_hangcheck_elapsed to be in the safe
side, regardless.

Or at minimum, copy the acthd read, seqno read ordering
into the i915_hangcheck_elapsed also.

-Mika


>       }
>  
>       i915_get_extra_instdone(dev, instdone);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 9762aa76bb0a..44d46018ee13 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2969,20 +2969,14 @@ i915_seqno_passed(uint32_t seq1, uint32_t seq2)
>       return (int32_t)(seq1 - seq2) >= 0;
>  }
>  
> -static inline bool i915_gem_request_started(struct drm_i915_gem_request *req,
> -                                        bool lazy_coherency)
> +static inline bool i915_gem_request_started(struct drm_i915_gem_request *req)
>  {
> -     if (!lazy_coherency && req->ring->irq_seqno_barrier)
> -             req->ring->irq_seqno_barrier(req->ring);
>       return i915_seqno_passed(req->ring->get_seqno(req->ring),
>                                req->previous_seqno);
>  }
>  
> -static inline bool i915_gem_request_completed(struct drm_i915_gem_request 
> *req,
> -                                           bool lazy_coherency)
> +static inline bool i915_gem_request_completed(struct drm_i915_gem_request 
> *req)
>  {
> -     if (!lazy_coherency && req->ring->irq_seqno_barrier)
> -             req->ring->irq_seqno_barrier(req->ring);
>       return i915_seqno_passed(req->ring->get_seqno(req->ring),
>                                req->seqno);
>  }
> @@ -3636,6 +3630,8 @@ static inline void i915_trace_irq_get(struct 
> intel_engine_cs *ring,
>  
>  static inline bool __i915_request_irq_complete(struct drm_i915_gem_request 
> *req)
>  {
> +     struct intel_engine_cs *engine = req->ring;
> +
>       /* Ensure our read of the seqno is coherent so that we
>        * do not "miss an interrupt" (i.e. if this is the last
>        * request and the seqno write from the GPU is not visible
> @@ -3647,7 +3643,10 @@ static inline bool __i915_request_irq_complete(struct 
> drm_i915_gem_request *req)
>        * but it is easier and safer to do it every time the waiter
>        * is woken.
>        */
> -     if (i915_gem_request_completed(req, false))
> +     if (engine->irq_seqno_barrier)
> +             engine->irq_seqno_barrier(engine);
> +
> +     if (i915_gem_request_completed(req))
>               return true;
>  
>       /* We need to check whether any gpu reset happened in between
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 4b26529f1f44..d125820c6309 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1171,12 +1171,12 @@ static bool __i915_spin_request(struct 
> drm_i915_gem_request *req,
>        */
>  
>       /* Only spin if we know the GPU is processing this request */
> -     if (!i915_gem_request_started(req, true))
> +     if (!i915_gem_request_started(req))
>               return false;
>  
>       timeout = local_clock_us(&cpu) + 5;
>       do {
> -             if (i915_gem_request_completed(req, true))
> +             if (i915_gem_request_completed(req))
>                       return true;
>  
>               if (signal_pending_state(state, wait->task))
> @@ -1228,7 +1228,7 @@ int __i915_wait_request(struct drm_i915_gem_request 
> *req,
>       if (list_empty(&req->list))
>               return 0;
>  
> -     if (i915_gem_request_completed(req, true))
> +     if (i915_gem_request_completed(req))
>               return 0;
>  
>       timeout_remain = MAX_SCHEDULE_TIMEOUT;
> @@ -2724,8 +2724,16 @@ i915_gem_find_active_request(struct intel_engine_cs 
> *ring)
>  {
>       struct drm_i915_gem_request *request;
>  
> +     /* We are called by the error capture and reset at a random
> +      * point in time. In particular, note that neither is crucially
> +      * ordered with an interrupt. After a hang, the GPU is dead and we
> +      * assume that no more writes can happen (we waited long enough for
> +      * all writes that were in transaction to be flushed) - adding an
> +      * extra delay for a recent interrupt is pointless. Hence, we do
> +      * not need an engine->irq_seqno_barrier() before the seqno reads.
> +      */
>       list_for_each_entry(request, &ring->request_list, list) {
> -             if (i915_gem_request_completed(request, false))
> +             if (i915_gem_request_completed(request))
>                       continue;
>  
>               return request;
> @@ -2859,7 +2867,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs 
> *ring)
>                                          struct drm_i915_gem_request,
>                                          list);
>  
> -             if (!i915_gem_request_completed(request, true))
> +             if (!i915_gem_request_completed(request))
>                       break;
>  
>               i915_gem_request_retire(request);
> @@ -2883,7 +2891,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs 
> *ring)
>       }
>  
>       if (unlikely(ring->trace_irq_req &&
> -                  i915_gem_request_completed(ring->trace_irq_req, true))) {
> +                  i915_gem_request_completed(ring->trace_irq_req))) {
>               ring->irq_put(ring);
>               i915_gem_request_assign(&ring->trace_irq_req, NULL);
>       }
> @@ -2995,7 +3003,7 @@ i915_gem_object_flush_active(struct drm_i915_gem_object 
> *obj)
>               if (list_empty(&req->list))
>                       goto retire;
>  
> -             if (i915_gem_request_completed(req, true)) {
> +             if (i915_gem_request_completed(req)) {
>                       __i915_gem_request_retire__upto(req);
>  retire:
>                       i915_gem_object_retire__read(obj, i);
> @@ -3104,7 +3112,7 @@ __i915_gem_object_sync(struct drm_i915_gem_object *obj,
>       if (to == from)
>               return 0;
>  
> -     if (i915_gem_request_completed(from_req, true))
> +     if (i915_gem_request_completed(from_req))
>               return 0;
>  
>       if (!i915_semaphore_is_enabled(obj->base.dev)) {
> diff --git a/drivers/gpu/drm/i915/intel_display.c 
> b/drivers/gpu/drm/i915/intel_display.c
> index 7e36f85d3109..de4d4a0d923a 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11523,7 +11523,7 @@ static bool __intel_pageflip_stall_check(struct 
> drm_device *dev,
>  
>       if (work->flip_ready_vblank == 0) {
>               if (work->flip_queued_req &&
> -                 !i915_gem_request_completed(work->flip_queued_req, true))
> +                 !i915_gem_request_completed(work->flip_queued_req))
>                       return false;
>  
>               work->flip_ready_vblank = drm_crtc_vblank_count(crtc);
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 9df9e9a22f3c..401c3770057d 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -7286,7 +7286,7 @@ static void __intel_rps_boost_work(struct work_struct 
> *work)
>       struct request_boost *boost = container_of(work, struct request_boost, 
> work);
>       struct drm_i915_gem_request *req = boost->req;
>  
> -     if (!i915_gem_request_completed(req, true))
> +     if (!i915_gem_request_completed(req))
>               gen6_rps_boost(to_i915(req->ring->dev), NULL,
>                              req->emitted_jiffies);
>  
> @@ -7302,7 +7302,7 @@ void intel_queue_rps_boost_for_request(struct 
> drm_device *dev,
>       if (req == NULL || INTEL_INFO(dev)->gen < 6)
>               return;
>  
> -     if (i915_gem_request_completed(req, true))
> +     if (i915_gem_request_completed(req))
>               return;
>  
>       boost = kmalloc(sizeof(*boost), GFP_ATOMIC);
> -- 
> 2.7.0.rc3
>
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