On Thu, Jul 12, 2012 at 04:13:35PM +0100, Chris Wilson wrote:
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>

I'd like to keep the analysis of why things blow up on the BUG_ON(seqno ==
0) here in the commit message, i.e. the two patches that together caused
the regression (I think we need both the flushing list prep patch an
-ERESTART from intel_ring_begin). Plus the scenario of what exactly needs
to be submitted and interrupted that you've laid out on irc.

Although I have to admit that I still fail to understand how the
unconditional flush can't plug all holes, i.e. if you come up with a
recipe to blow things up with only that broken patch applied, I'd much
appreciate it ;-)

/me feels way to dense about all the complexity we have here

One thing popped out a bit while reading this patch again, comment below.

Thanks, Daniel
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c   |    7 ----
>  drivers/gpu/drm/i915/i915_drv.h       |   19 +++--------
>  drivers/gpu/drm/i915/i915_gem.c       |   57 
> ++++++---------------------------
>  drivers/gpu/drm/i915/i915_gem_evict.c |   20 ------------
>  4 files changed, 13 insertions(+), 90 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
> b/drivers/gpu/drm/i915/i915_debugfs.c
> index 359f6e8..d149890 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -44,7 +44,6 @@
>  
>  enum {
>       ACTIVE_LIST,
> -     FLUSHING_LIST,
>       INACTIVE_LIST,
>       PINNED_LIST,
>  };
> @@ -177,10 +176,6 @@ static int i915_gem_object_list_info(struct seq_file *m, 
> void *data)
>               seq_printf(m, "Inactive:\n");
>               head = &dev_priv->mm.inactive_list;
>               break;
> -     case FLUSHING_LIST:
> -             seq_printf(m, "Flushing:\n");
> -             head = &dev_priv->mm.flushing_list;
> -             break;
>       default:
>               mutex_unlock(&dev->struct_mutex);
>               return -EINVAL;
> @@ -238,7 +233,6 @@ static int i915_gem_object_info(struct seq_file *m, void* 
> data)
>  
>       size = count = mappable_size = mappable_count = 0;
>       count_objects(&dev_priv->mm.active_list, mm_list);
> -     count_objects(&dev_priv->mm.flushing_list, mm_list);
>       seq_printf(m, "  %u [%u] active objects, %zu [%zu] bytes\n",
>                  count, mappable_count, size, mappable_size);
>  
> @@ -2006,7 +2000,6 @@ static struct drm_info_list i915_debugfs_list[] = {
>       {"i915_gem_gtt", i915_gem_gtt_info, 0},
>       {"i915_gem_pinned", i915_gem_gtt_info, 0, (void *) PINNED_LIST},
>       {"i915_gem_active", i915_gem_object_list_info, 0, (void *) ACTIVE_LIST},
> -     {"i915_gem_flushing", i915_gem_object_list_info, 0, (void *) 
> FLUSHING_LIST},
>       {"i915_gem_inactive", i915_gem_object_list_info, 0, (void *) 
> INACTIVE_LIST},
>       {"i915_gem_pageflip", i915_gem_pageflip_info, 0},
>       {"i915_gem_request", i915_gem_request_info, 0},
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 51e234e..38b95be 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -696,17 +696,6 @@ typedef struct drm_i915_private {
>               struct list_head active_list;
>  
>               /**
> -              * List of objects which are not in the ringbuffer but which
> -              * still have a write_domain which needs to be flushed before
> -              * unbinding.
> -              *
> -              * last_rendering_seqno is 0 while an object is in this list.
> -              *
> -              * A reference is held on the buffer while on this list.
> -              */
> -             struct list_head flushing_list;
> -
> -             /**
>                * LRU list of objects which are not in the ringbuffer and
>                * are ready to unbind, but are still in the GTT.
>                *
> @@ -873,7 +862,7 @@ struct drm_i915_gem_object {
>       struct drm_mm_node *gtt_space;
>       struct list_head gtt_list;
>  
> -     /** This object's place on the active/flushing/inactive lists */
> +     /** This object's place on the active/inactive lists */
>       struct list_head ring_list;
>       struct list_head mm_list;
>       /** This object's place on GPU write list */
> @@ -882,9 +871,9 @@ struct drm_i915_gem_object {
>       struct list_head exec_list;
>  
>       /**
> -      * This is set if the object is on the active or flushing lists
> -      * (has pending rendering), and is not set if it's on inactive (ready
> -      * to be unbound).
> +      * This is set if the object is on the active lists (has pending
> +      * rendering and so a non-zero seqno), and is not set if it i s on
> +      * inactive (ready to be unbound) list.
>        */
>       unsigned int active:1;
>  
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 875b745..f69d897 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1458,26 +1458,6 @@ i915_gem_object_move_to_active(struct 
> drm_i915_gem_object *obj,
>  }
>  
>  static void
> -i915_gem_object_move_off_active(struct drm_i915_gem_object *obj)
> -{
> -     list_del_init(&obj->ring_list);
> -     obj->last_rendering_seqno = 0;
> -     obj->last_fenced_seqno = 0;
> -}
> -
> -static void
> -i915_gem_object_move_to_flushing(struct drm_i915_gem_object *obj)
> -{
> -     struct drm_device *dev = obj->base.dev;
> -     drm_i915_private_t *dev_priv = dev->dev_private;
> -
> -     BUG_ON(!obj->active);
> -     list_move_tail(&obj->mm_list, &dev_priv->mm.flushing_list);
> -
> -     i915_gem_object_move_off_active(obj);
> -}
> -
> -static void
>  i915_gem_object_move_to_inactive(struct drm_i915_gem_object *obj)
>  {
>       struct drm_device *dev = obj->base.dev;
> @@ -1487,13 +1467,18 @@ i915_gem_object_move_to_inactive(struct 
> drm_i915_gem_object *obj)
>  
>       BUG_ON(!list_empty(&obj->gpu_write_list));
>       BUG_ON(!obj->active);
> +
> +     list_del_init(&obj->ring_list);
>       obj->ring = NULL;
>  
> -     i915_gem_object_move_off_active(obj);
> +     obj->last_rendering_seqno = 0;
> +     obj->last_fenced_seqno = 0;
>       obj->fenced_gpu_access = false;
>  
> -     obj->active = 0;
> +     obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;

Clearing the write_domain here makes me rather uneasy ... I see that we
should plug gpu write domains leaking out of obj->active (at least until
we've ripped out all that gpu domain tracking complexity for good). But I
also fear that this papers over some issues - at least in the old code we
should never be able to see this. Maybe just add a comment to explain
what's going on?

>       obj->pending_gpu_write = false;
> +
> +     obj->active = 0;
>       drm_gem_object_unreference(&obj->base);
>  
>       WARN_ON(i915_verify_lists(dev));
> @@ -1728,20 +1713,6 @@ void i915_gem_reset(struct drm_device *dev)
>       for_each_ring(ring, dev_priv, i)
>               i915_gem_reset_ring_lists(dev_priv, ring);
>  
> -     /* Remove anything from the flushing lists. The GPU cache is likely
> -      * to be lost on reset along with the data, so simply move the
> -      * lost bo to the inactive list.
> -      */
> -     while (!list_empty(&dev_priv->mm.flushing_list)) {
> -             obj = list_first_entry(&dev_priv->mm.flushing_list,
> -                                   struct drm_i915_gem_object,
> -                                   mm_list);
> -
> -             obj->base.write_domain = 0;
> -             list_del_init(&obj->gpu_write_list);
> -             i915_gem_object_move_to_inactive(obj);
> -     }
> -
>       /* Move everything out of the GPU domains to ensure we do any
>        * necessary invalidation upon reuse.
>        */
> @@ -1812,10 +1783,7 @@ i915_gem_retire_requests_ring(struct intel_ring_buffer 
> *ring)
>               if (!i915_seqno_passed(seqno, obj->last_rendering_seqno))
>                       break;
>  
> -             if (obj->base.write_domain != 0)
> -                     i915_gem_object_move_to_flushing(obj);
> -             else
> -                     i915_gem_object_move_to_inactive(obj);
> +             i915_gem_object_move_to_inactive(obj);
>       }
>  
>       if (unlikely(ring->trace_irq_seqno &&
> @@ -3877,7 +3845,6 @@ i915_gem_entervt_ioctl(struct drm_device *dev, void 
> *data,
>       }
>  
>       BUG_ON(!list_empty(&dev_priv->mm.active_list));
> -     BUG_ON(!list_empty(&dev_priv->mm.flushing_list));
>       BUG_ON(!list_empty(&dev_priv->mm.inactive_list));
>       mutex_unlock(&dev->struct_mutex);
>  
> @@ -3935,7 +3902,6 @@ i915_gem_load(struct drm_device *dev)
>       drm_i915_private_t *dev_priv = dev->dev_private;
>  
>       INIT_LIST_HEAD(&dev_priv->mm.active_list);
> -     INIT_LIST_HEAD(&dev_priv->mm.flushing_list);
>       INIT_LIST_HEAD(&dev_priv->mm.inactive_list);
>       INIT_LIST_HEAD(&dev_priv->mm.fence_list);
>       INIT_LIST_HEAD(&dev_priv->mm.gtt_list);
> @@ -4186,12 +4152,7 @@ static int
>  i915_gpu_is_active(struct drm_device *dev)
>  {
>       drm_i915_private_t *dev_priv = dev->dev_private;
> -     int lists_empty;
> -
> -     lists_empty = list_empty(&dev_priv->mm.flushing_list) &&
> -                   list_empty(&dev_priv->mm.active_list);
> -
> -     return !lists_empty;
> +     return !list_empty(&dev_priv->mm.active_list);
>  }
>  
>  static int
> diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c 
> b/drivers/gpu/drm/i915/i915_gem_evict.c
> index ae7c24e..f61af59 100644
> --- a/drivers/gpu/drm/i915/i915_gem_evict.c
> +++ b/drivers/gpu/drm/i915/i915_gem_evict.c
> @@ -92,23 +92,6 @@ i915_gem_evict_something(struct drm_device *dev, int 
> min_size,
>  
>       /* Now merge in the soon-to-be-expired objects... */
>       list_for_each_entry(obj, &dev_priv->mm.active_list, mm_list) {
> -             /* Does the object require an outstanding flush? */
> -             if (obj->base.write_domain)
> -                     continue;
> -
> -             if (mark_free(obj, &unwind_list))
> -                     goto found;
> -     }
> -
> -     /* Finally add anything with a pending flush (in order of retirement) */
> -     list_for_each_entry(obj, &dev_priv->mm.flushing_list, mm_list) {
> -             if (mark_free(obj, &unwind_list))
> -                     goto found;
> -     }
> -     list_for_each_entry(obj, &dev_priv->mm.active_list, mm_list) {
> -             if (!obj->base.write_domain)
> -                     continue;
> -
>               if (mark_free(obj, &unwind_list))
>                       goto found;
>       }
> @@ -171,7 +154,6 @@ i915_gem_evict_everything(struct drm_device *dev, bool 
> purgeable_only)
>       int ret;
>  
>       lists_empty = (list_empty(&dev_priv->mm.inactive_list) &&
> -                    list_empty(&dev_priv->mm.flushing_list) &&
>                      list_empty(&dev_priv->mm.active_list));
>       if (lists_empty)
>               return -ENOSPC;
> @@ -188,8 +170,6 @@ i915_gem_evict_everything(struct drm_device *dev, bool 
> purgeable_only)
>  
>       i915_gem_retire_requests(dev);
>  
> -     BUG_ON(!list_empty(&dev_priv->mm.flushing_list));
> -
>       /* Having flushed everything, unbind() should never raise an error */
>       list_for_each_entry_safe(obj, next,
>                                &dev_priv->mm.inactive_list, mm_list) {
> -- 
> 1.7.10.4
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Mail: dan...@ffwll.ch
Mobile: +41 (0)79 365 57 48
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