An old optimisation to reduce the number of atomics per batch sadly
relies on struct_mutex for coordination. In order to remove struct_mutex
from serialising object/context closing, always taking and releasing an
active reference on first use / last use greatly simplifies the locking.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.a...@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c   |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_object.c    | 13 +---------
 drivers/gpu/drm/i915/gem/i915_gem_object.h    | 24 +------------------
 .../gpu/drm/i915/gem/i915_gem_object_types.h  |  8 -------
 .../gpu/drm/i915/gem/selftests/huge_pages.c   |  3 +--
 .../i915/gem/selftests/i915_gem_coherency.c   |  4 ++--
 .../drm/i915/gem/selftests/i915_gem_context.c | 11 +++++----
 .../drm/i915/gem/selftests/i915_gem_mman.c    |  2 +-
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     |  2 +-
 drivers/gpu/drm/i915/gt/intel_ringbuffer.c    |  3 +--
 drivers/gpu/drm/i915/gt/selftest_hangcheck.c  |  9 +------
 .../gpu/drm/i915/gt/selftest_workarounds.c    |  3 ---
 drivers/gpu/drm/i915/gvt/scheduler.c          |  2 +-
 drivers/gpu/drm/i915/i915_gem_batch_pool.c    |  2 +-
 drivers/gpu/drm/i915/i915_gem_render_state.c  |  2 +-
 drivers/gpu/drm/i915/i915_vma.c               | 15 +++++-------
 drivers/gpu/drm/i915/selftests/i915_request.c |  8 -------
 drivers/gpu/drm/i915/selftests/igt_spinner.c  |  9 +------
 18 files changed, 26 insertions(+), 96 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 217d87c13cd8..5016a3e1f863 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -112,7 +112,7 @@ static void lut_close(struct i915_gem_context *ctx)
                radix_tree_iter_delete(&ctx->handles_vma, &iter, slot);
 
                vma->open_count--;
-               __i915_gem_object_release_unless_active(vma->obj);
+               i915_vma_put(vma);
        }
        rcu_read_unlock();
 }
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c 
b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index df79e2eead62..c178cf7614c6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -156,7 +156,7 @@ void i915_gem_close_object(struct drm_gem_object *gem, 
struct drm_file *file)
                list_del(&lut->ctx_link);
 
                i915_lut_handle_free(lut);
-               __i915_gem_object_release_unless_active(obj);
+               i915_gem_object_put(obj);
        }
 
        mutex_unlock(&i915->drm.struct_mutex);
@@ -348,17 +348,6 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
        call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
 }
 
-void __i915_gem_object_release_unless_active(struct drm_i915_gem_object *obj)
-{
-       lockdep_assert_held(&obj->base.dev->struct_mutex);
-
-       if (!i915_gem_object_has_active_reference(obj) &&
-           i915_gem_object_is_active(obj))
-               i915_gem_object_set_active_reference(obj);
-       else
-               i915_gem_object_put(obj);
-}
-
 static inline enum fb_op_origin
 fb_write_origin(struct drm_i915_gem_object *obj, unsigned int domain)
 {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h 
b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 23bca003fbfb..dcb765cd97a3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -161,31 +161,9 @@ i915_gem_object_needs_async_cancel(const struct 
drm_i915_gem_object *obj)
 static inline bool
 i915_gem_object_is_active(const struct drm_i915_gem_object *obj)
 {
-       return obj->active_count;
+       return READ_ONCE(obj->active_count);
 }
 
-static inline bool
-i915_gem_object_has_active_reference(const struct drm_i915_gem_object *obj)
-{
-       return test_bit(I915_BO_ACTIVE_REF, &obj->flags);
-}
-
-static inline void
-i915_gem_object_set_active_reference(struct drm_i915_gem_object *obj)
-{
-       lockdep_assert_held(&obj->base.dev->struct_mutex);
-       __set_bit(I915_BO_ACTIVE_REF, &obj->flags);
-}
-
-static inline void
-i915_gem_object_clear_active_reference(struct drm_i915_gem_object *obj)
-{
-       lockdep_assert_held(&obj->base.dev->struct_mutex);
-       __clear_bit(I915_BO_ACTIVE_REF, &obj->flags);
-}
-
-void __i915_gem_object_release_unless_active(struct drm_i915_gem_object *obj);
-
 static inline bool
 i915_gem_object_is_framebuffer(const struct drm_i915_gem_object *obj)
 {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h 
b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 24abdd6999b5..133581339d81 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -120,14 +120,6 @@ struct drm_i915_gem_object {
        struct list_head batch_pool_link;
        I915_SELFTEST_DECLARE(struct list_head st_link);
 
-       unsigned long flags;
-
-       /**
-        * Have we taken a reference for the object for incomplete GPU
-        * activity?
-        */
-#define I915_BO_ACTIVE_REF 0
-
        /*
         * Is the object to be mapped as read-only to the GPU
         * Only honoured if hardware has relevant pte bit
diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c 
b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index 5a89cbab3b2e..9e211aa044ea 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -975,8 +975,6 @@ static int gpu_write(struct i915_vma *vma,
        if (err)
                goto err_request;
 
-       i915_gem_object_set_active_reference(batch->obj);
-
        i915_vma_lock(vma);
        err = i915_gem_object_set_to_gtt_domain(vma->obj, false);
        if (err == 0)
@@ -995,6 +993,7 @@ static int gpu_write(struct i915_vma *vma,
 err_batch:
        i915_vma_unpin(batch);
        i915_vma_close(batch);
+       i915_vma_put(batch);
 
        return err;
 }
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c 
b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
index 22fe4b6fd506..ae9586645150 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
@@ -365,7 +365,7 @@ static int igt_gem_coherency(void *arg)
                                                }
                                        }
 
-                                       
__i915_gem_object_release_unless_active(obj);
+                                       i915_gem_object_put(obj);
                                }
                        }
                }
@@ -377,7 +377,7 @@ static int igt_gem_coherency(void *arg)
        return err;
 
 put_object:
-       __i915_gem_object_release_unless_active(obj);
+       i915_gem_object_put(obj);
        goto unlock;
 }
 
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c 
b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
index 72eedd6c2a0a..1bc3b8026400 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -318,14 +318,14 @@ static int gpu_fill(struct drm_i915_gem_object *obj,
        if (err)
                goto skip_request;
 
-       i915_gem_object_set_active_reference(batch->obj);
+       i915_request_add(rq);
+
        i915_vma_unpin(batch);
        i915_vma_close(batch);
+       i915_vma_put(batch);
 
        i915_vma_unpin(vma);
 
-       i915_request_add(rq);
-
        return 0;
 
 skip_request:
@@ -802,9 +802,9 @@ emit_rpcs_query(struct drm_i915_gem_object *obj,
        if (err)
                goto skip_request;
 
-       i915_gem_object_set_active_reference(batch->obj);
        i915_vma_unpin(batch);
        i915_vma_close(batch);
+       i915_vma_put(batch);
 
        i915_vma_unpin(vma);
 
@@ -820,6 +820,7 @@ emit_rpcs_query(struct drm_i915_gem_object *obj,
        i915_request_add(rq);
 err_batch:
        i915_vma_unpin(batch);
+       i915_vma_put(batch);
 err_vma:
        i915_vma_unpin(vma);
 
@@ -1365,9 +1366,9 @@ static int write_to_scratch(struct i915_gem_context *ctx,
        if (err)
                goto skip_request;
 
-       i915_gem_object_set_active_reference(obj);
        i915_vma_unpin(vma);
        i915_vma_close(vma);
+       i915_vma_put(vma);
 
        i915_request_add(rq);
 
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c 
b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
index 297f8864d392..5db3327958fb 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
@@ -354,8 +354,8 @@ static int make_obj_busy(struct drm_i915_gem_object *obj)
 
        i915_request_add(rq);
 
-       __i915_gem_object_release_unless_active(obj);
        i915_vma_unpin(vma);
+       i915_gem_object_put(obj); /* leave it only alive via its active ref */
 
        return err;
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c 
b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index c397ec1b3df9..4d911f60d1f8 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -477,7 +477,7 @@ static void cleanup_status_page(struct intel_engine_cs 
*engine)
                i915_vma_unpin(vma);
 
        i915_gem_object_unpin_map(vma->obj);
-       __i915_gem_object_release_unless_active(vma->obj);
+       i915_gem_object_put(vma->obj);
 }
 
 static int pin_ggtt_status_page(struct intel_engine_cs *engine,
diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index 66d5a52d505c..ff58d658e3e2 100644
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -1302,10 +1302,9 @@ intel_engine_create_ring(struct intel_engine_cs *engine,
 void intel_ring_free(struct kref *ref)
 {
        struct intel_ring *ring = container_of(ref, typeof(*ring), ref);
-       struct drm_i915_gem_object *obj = ring->vma->obj;
 
        i915_vma_close(ring->vma);
-       __i915_gem_object_release_unless_active(obj);
+       i915_vma_put(ring->vma);
 
        i915_timeline_put(ring->timeline);
        kfree(ring);
diff --git a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c 
b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
index 45745e36b5f4..910f96231934 100644
--- a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
+++ b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
@@ -118,15 +118,8 @@ static int move_to_active(struct i915_vma *vma,
        i915_vma_lock(vma);
        err = i915_vma_move_to_active(vma, rq, flags);
        i915_vma_unlock(vma);
-       if (err)
-               return err;
-
-       if (!i915_gem_object_has_active_reference(vma->obj)) {
-               i915_gem_object_get(vma->obj);
-               i915_gem_object_set_active_reference(vma->obj);
-       }
 
-       return 0;
+       return err;
 }
 
 static struct i915_request *
diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c 
b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
index d4ba5296b2c8..db40d4f805ea 100644
--- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
@@ -135,9 +135,6 @@ read_nonprivs(struct i915_gem_context *ctx, struct 
intel_engine_cs *engine)
        }
        intel_ring_advance(rq, cs);
 
-       i915_gem_object_get(result);
-       i915_gem_object_set_active_reference(result);
-
        i915_request_add(rq);
        i915_vma_unpin(vma);
 
diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c 
b/drivers/gpu/drm/i915/gvt/scheduler.c
index 840cac06add7..d4dc0e189547 100644
--- a/drivers/gpu/drm/i915/gvt/scheduler.c
+++ b/drivers/gpu/drm/i915/gvt/scheduler.c
@@ -583,7 +583,7 @@ static void release_shadow_batch_buffer(struct 
intel_vgpu_workload *workload)
                                i915_vma_unpin(bb->vma);
                                i915_vma_close(bb->vma);
                        }
-                       __i915_gem_object_release_unless_active(bb->obj);
+                       i915_gem_object_put(bb->obj);
                }
                list_del(&bb->list);
                kfree(bb);
diff --git a/drivers/gpu/drm/i915/i915_gem_batch_pool.c 
b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
index f3890b664e3f..56adfdcaed3e 100644
--- a/drivers/gpu/drm/i915/i915_gem_batch_pool.c
+++ b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
@@ -55,7 +55,7 @@ void i915_gem_batch_pool_fini(struct i915_gem_batch_pool 
*pool)
                list_for_each_entry_safe(obj, next,
                                         &pool->cache_list[n],
                                         batch_pool_link)
-                       __i915_gem_object_release_unless_active(obj);
+                       i915_gem_object_put(obj);
 
                INIT_LIST_HEAD(&pool->cache_list[n]);
        }
diff --git a/drivers/gpu/drm/i915/i915_gem_render_state.c 
b/drivers/gpu/drm/i915/i915_gem_render_state.c
index 706ed71468e8..4ee032072d4f 100644
--- a/drivers/gpu/drm/i915/i915_gem_render_state.c
+++ b/drivers/gpu/drm/i915/i915_gem_render_state.c
@@ -230,6 +230,6 @@ int i915_gem_render_state_emit(struct i915_request *rq)
 err_vma:
        i915_vma_close(so.vma);
 err_obj:
-       __i915_gem_object_release_unless_active(so.obj);
+       i915_gem_object_put(so.obj);
        return err;
 }
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 3620d39c0bc8..16d47f1f645a 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -115,10 +115,7 @@ static void __i915_vma_retire(struct i915_active *ref)
         */
        obj_bump_mru(obj);
 
-       if (i915_gem_object_has_active_reference(obj)) {
-               i915_gem_object_clear_active_reference(obj);
-               i915_gem_object_put(obj);
-       }
+       i915_gem_object_put(obj); /* and drop the active reference */
 }
 
 static struct i915_vma *
@@ -443,7 +440,7 @@ void i915_vma_unpin_and_release(struct i915_vma **p_vma, 
unsigned int flags)
        if (flags & I915_VMA_RELEASE_MAP)
                i915_gem_object_unpin_map(obj);
 
-       __i915_gem_object_release_unless_active(obj);
+       i915_gem_object_put(obj);
 }
 
 bool i915_vma_misplaced(const struct i915_vma *vma,
@@ -940,12 +937,12 @@ int i915_vma_move_to_active(struct i915_vma *vma,
         * add the active reference first and queue for it to be dropped
         * *last*.
         */
-       if (!vma->active.count)
-               obj->active_count++;
+       if (!vma->active.count && !obj->active_count++)
+               i915_gem_object_get(obj); /* once more for the active ref */
 
        if (unlikely(i915_active_ref(&vma->active, rq->fence.context, rq))) {
-               if (!vma->active.count)
-                       obj->active_count--;
+               if (!vma->active.count && !--obj->active_count)
+                       i915_gem_object_put(obj);
                return -ENOMEM;
        }
 
diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c 
b/drivers/gpu/drm/i915/selftests/i915_request.c
index 1b9c183920aa..693ea097c05f 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -870,11 +870,6 @@ static int live_all_engines(void *arg)
                GEM_BUG_ON(err);
                request[id]->batch = batch;
 
-               if (!i915_gem_object_has_active_reference(batch->obj)) {
-                       i915_gem_object_get(batch->obj);
-                       i915_gem_object_set_active_reference(batch->obj);
-               }
-
                i915_vma_lock(batch);
                err = i915_vma_move_to_active(batch, request[id], 0);
                i915_vma_unlock(batch);
@@ -997,9 +992,6 @@ static int live_sequential_engines(void *arg)
                i915_vma_unlock(batch);
                GEM_BUG_ON(err);
 
-               i915_gem_object_set_active_reference(batch->obj);
-               i915_vma_get(batch);
-
                i915_request_get(request[id]);
                i915_request_add(request[id]);
 
diff --git a/drivers/gpu/drm/i915/selftests/igt_spinner.c 
b/drivers/gpu/drm/i915/selftests/igt_spinner.c
index d845d1dc7ce7..02306aa83d2a 100644
--- a/drivers/gpu/drm/i915/selftests/igt_spinner.c
+++ b/drivers/gpu/drm/i915/selftests/igt_spinner.c
@@ -79,15 +79,8 @@ static int move_to_active(struct i915_vma *vma,
        i915_vma_lock(vma);
        err = i915_vma_move_to_active(vma, rq, flags);
        i915_vma_unlock(vma);
-       if (err)
-               return err;
-
-       if (!i915_gem_object_has_active_reference(vma->obj)) {
-               i915_gem_object_get(vma->obj);
-               i915_gem_object_set_active_reference(vma->obj);
-       }
 
-       return 0;
+       return err;
 }
 
 struct i915_request *
-- 
2.20.1

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