Re: [PATCH 3/3] drm/i915: Markup expected timeline locks for i915_active

Mika Kuoppala
2019-08-16T12:03:06Z

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

> As every i915_active_request should be serialised by a dedicated lock,
> i915_active consists of a tree of locks; one for each node. Markup up
> the i915_active_request with what lock is supposed to be guarding it so
> that we can verify that the serialised updated are indeed serialised.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
> drivers/gpu/drm/i915/display/intel_overlay.c | 2 +-
> .../gpu/drm/i915/gem/i915_gem_client_blt.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_context.c | 2 +-
> drivers/gpu/drm/i915/gt/intel_context.c | 11 +++--------
> drivers/gpu/drm/i915/gt/intel_engine_pool.h | 2 +-
> drivers/gpu/drm/i915/gt/intel_timeline.c | 7 +++----
> drivers/gpu/drm/i915/gt/selftest_timeline.c | 4 ++++
> .../gpu/drm/i915/gt/selftests/mock_timeline.c | 2 +-
> drivers/gpu/drm/i915/i915_active.c | 19 +++++++++++++++----
> drivers/gpu/drm/i915/i915_active.h | 12 ++++++++++--
> drivers/gpu/drm/i915/i915_active_types.h | 3 +++
> drivers/gpu/drm/i915/i915_vma.c | 4 ++--
> drivers/gpu/drm/i915/selftests/i915_active.c | 3 +--
> 13 files changed, 46 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_overlay.c b/drivers/gpu/drm/i915/display/intel_overlay.c
> index e1248eace0e1..eca41c4a5aa6 100644
> --- a/drivers/gpu/drm/i915/display/intel_overlay.c
> +++ b/drivers/gpu/drm/i915/display/intel_overlay.c
> @@ -230,7 +230,7 @@ alloc_request(struct intel_overlay *overlay, void (*fn)(struct intel_overlay *))
> if (IS_ERR(rq))
> return rq;
>
> - err = i915_active_ref(&overlay->last_flip, rq->fence.context, rq);
> + err = i915_active_ref(&overlay->last_flip, rq->timeline, rq);
> if (err) {
> i915_request_add(rq);
> return ERR_PTR(err);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> index 6a4e84157bf2..818ac6915bc5 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> @@ -211,7 +211,7 @@ static void clear_pages_worker(struct work_struct *work)
> * keep track of the GPU activity within this vma/request, and
> * propagate the signal from the request to w->dma.
> */
> - err = i915_active_ref(&vma->active, rq->fence.context, rq);
> + err = i915_active_ref(&vma->active, rq->timeline, rq);
> if (err)
> goto out_request;
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index a6b0cb714292..cd1fd2e5423a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -908,7 +908,7 @@ static int context_barrier_task(struct i915_gem_context *ctx,
> if (emit)
> err = emit(rq, data);
> if (err == 0)
> - err = i915_active_ref(&cb->base, rq->fence.context, rq);
> + err = i915_active_ref(&cb->base, rq->timeline, rq);
>
> i915_request_add(rq);
> if (err)
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 9114953bf920..f55691d151ae 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -306,10 +306,10 @@ int intel_context_prepare_remote_request(struct intel_context *ce,
>
> /* Queue this switch after current activity by this context. */
> err = i915_active_request_set(&tl->last_request, rq);
> + mutex_unlock(&tl->mutex);
> if (err)
> - goto unlock;
> + return err;
> }
> - lockdep_assert_held(&tl->mutex);
>
> /*
> * Guarantee context image and the timeline remains pinned until the
> @@ -319,12 +319,7 @@ int intel_context_prepare_remote_request(struct intel_context *ce,
> * words transfer the pinned ce object to tracked active request.
> */
> GEM_BUG_ON(i915_active_is_idle(&ce->active));
> - err = i915_active_ref(&ce->active, rq->fence.context, rq);
> -
> -unlock:
> - if (rq->timeline != tl)
> - mutex_unlock(&tl->mutex);
> - return err;
> + return i915_active_ref(&ce->active, rq->timeline, rq);

There seem to have been so much work here for no apparent gains.
Good riddance.

> }
>
> struct i915_request *intel_context_create_request(struct intel_context *ce)
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pool.h b/drivers/gpu/drm/i915/gt/intel_engine_pool.h
> index f7a0a660c1c9..8d069efd9457 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pool.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pool.h
> @@ -18,7 +18,7 @@ static inline int
> intel_engine_pool_mark_active(struct intel_engine_pool_node *node,
> struct i915_request *rq)
> {
> - return i915_active_ref(&node->active, rq->fence.context, rq);
> + return i915_active_ref(&node->active, rq->timeline, rq);
> }
>
> static inline void
> diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c b/drivers/gpu/drm/i915/gt/intel_timeline.c
> index eafd94d5e211..02fbe11b671b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_timeline.c
> +++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
> @@ -254,7 +254,7 @@ int intel_timeline_init(struct intel_timeline *timeline,
>
> mutex_init(&timeline->mutex);
>
> - INIT_ACTIVE_REQUEST(&timeline->last_request);
> + INIT_ACTIVE_REQUEST(&timeline->last_request, &timeline->mutex);
> INIT_LIST_HEAD(&timeline->requests);
>
> i915_syncmap_init(&timeline->sync);
> @@ -440,8 +440,7 @@ __intel_timeline_get_seqno(struct intel_timeline *tl,
> * free it after the current request is retired, which ensures that
> * all writes into the cacheline from previous requests are complete.
> */
> - err = i915_active_ref(&tl->hwsp_cacheline->active,
> - tl->fence_context, rq);
> + err = i915_active_ref(&tl->hwsp_cacheline->active, tl, rq);
> if (err)
> goto err_cacheline;
>
> @@ -492,7 +491,7 @@ int intel_timeline_get_seqno(struct intel_timeline *tl,
> static int cacheline_ref(struct intel_timeline_cacheline *cl,
> struct i915_request *rq)
> {
> - return i915_active_ref(&cl->active, rq->fence.context, rq);
> + return i915_active_ref(&cl->active, rq->timeline, rq);
> }
>
> int intel_timeline_read_hwsp(struct i915_request *from,
> diff --git a/drivers/gpu/drm/i915/gt/selftest_timeline.c b/drivers/gpu/drm/i915/gt/selftest_timeline.c
> index d54113697745..321481403165 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_timeline.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_timeline.c
> @@ -689,7 +689,9 @@ static int live_hwsp_wrap(void *arg)
>
> tl->seqno = -4u;
>
> + mutex_lock_nested(&tl->mutex, SINGLE_DEPTH_NESTING);
> err = intel_timeline_get_seqno(tl, rq, &seqno[0]);
> + mutex_unlock(&tl->mutex);
> if (err) {
> i915_request_add(rq);
> goto out;
> @@ -704,7 +706,9 @@ static int live_hwsp_wrap(void *arg)
> }
> hwsp_seqno[0] = tl->hwsp_seqno;
>
> + mutex_lock_nested(&tl->mutex, SINGLE_DEPTH_NESTING);
> err = intel_timeline_get_seqno(tl, rq, &seqno[1]);
> + mutex_unlock(&tl->mutex);
> if (err) {
> i915_request_add(rq);
> goto out;
> diff --git a/drivers/gpu/drm/i915/gt/selftests/mock_timeline.c b/drivers/gpu/drm/i915/gt/selftests/mock_timeline.c
> index 5c549205828a..598170efcaf6 100644
> --- a/drivers/gpu/drm/i915/gt/selftests/mock_timeline.c
> +++ b/drivers/gpu/drm/i915/gt/selftests/mock_timeline.c
> @@ -15,7 +15,7 @@ void mock_timeline_init(struct intel_timeline *timeline, u64 context)
>
> mutex_init(&timeline->mutex);
>
> - INIT_ACTIVE_REQUEST(&timeline->last_request);
> + INIT_ACTIVE_REQUEST(&timeline->last_request, &timeline->mutex);
> INIT_LIST_HEAD(&timeline->requests);
>
> i915_syncmap_init(&timeline->sync);
> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
> index 2439c4f62ad8..df6164591702 100644
> --- a/drivers/gpu/drm/i915/i915_active.c
> +++ b/drivers/gpu/drm/i915/i915_active.c
> @@ -169,10 +169,11 @@ node_retire(struct i915_active_request *base, struct i915_request *rq)
> }
>
> static struct i915_active_request *
> -active_instance(struct i915_active *ref, u64 idx)
> +active_instance(struct i915_active *ref, struct intel_timeline *tl)
> {
> struct active_node *node, *prealloc;
> struct rb_node **p, *parent;
> + u64 idx = tl->fence_context;
>
> /*
> * We track the most recently used timeline to skip a rbtree search
> @@ -211,7 +212,7 @@ active_instance(struct i915_active *ref, u64 idx)
> }
>
> node = prealloc;
> - i915_active_request_init(&node->base, NULL, node_retire);
> + i915_active_request_init(&node->base, &tl->mutex, NULL, node_retire);
> node->ref = ref;
> node->timeline = idx;
>
> @@ -294,18 +295,20 @@ __active_del_barrier(struct i915_active *ref, struct active_node *node)
> }
>
> int i915_active_ref(struct i915_active *ref,
> - u64 timeline,
> + struct intel_timeline *tl,
> struct i915_request *rq)
> {
> struct i915_active_request *active;
> int err;
>
> + lockdep_assert_held(&tl->mutex);
> +
> /* Prevent reaping in case we malloc/wait while building the tree */
> err = i915_active_acquire(ref);
> if (err)
> return err;
>
> - active = active_instance(ref, timeline);
> + active = active_instance(ref, tl);
> if (!active) {
> err = -ENOMEM;
> goto out;
> @@ -596,6 +599,10 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
> goto unwind;
> }
>
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> + node->base.lock =
> + &engine->kernel_context->timeline->mutex;
> +#endif
> RCU_INIT_POINTER(node->base.request, NULL);
> node->base.retire = node_retire;
> node->timeline = idx;
> @@ -701,6 +708,10 @@ int i915_active_request_set(struct i915_active_request *active,
> {
> int err;
>
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> + lockdep_assert_held(active->lock);
> +#endif
> +
> /* Must maintain ordering wrt previous active requests */
> err = i915_request_await_active_request(rq, active);
> if (err)
> diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
> index f6d730cf2fe6..f95058f99057 100644
> --- a/drivers/gpu/drm/i915/i915_active.h
> +++ b/drivers/gpu/drm/i915/i915_active.h
> @@ -58,15 +58,20 @@ void i915_active_retire_noop(struct i915_active_request *active,
> */
> static inline void
> i915_active_request_init(struct i915_active_request *active,
> + struct mutex *lock,
> struct i915_request *rq,
> i915_active_retire_fn retire)
> {
> RCU_INIT_POINTER(active->request, rq);
> INIT_LIST_HEAD(&active->link);
> active->retire = retire ?: i915_active_retire_noop;
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> + active->lock = lock;
> +#endif
> }
>
> -#define INIT_ACTIVE_REQUEST(name) i915_active_request_init((name), NULL, NULL)
> +#define INIT_ACTIVE_REQUEST(name, lock) \
> + i915_active_request_init((name), (lock), NULL, NULL)
>
> /**
> * i915_active_request_set - updates the tracker to watch the current request
> @@ -81,6 +86,9 @@ static inline void
> __i915_active_request_set(struct i915_active_request *active,
> struct i915_request *request)
> {
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> + lockdep_assert_held(active->lock);
> +#endif
> list_move(&active->link, &request->active_list);
> rcu_assign_pointer(active->request, request);
> }
> @@ -362,7 +370,7 @@ void __i915_active_init(struct drm_i915_private *i915,
> } while (0)
>
> int i915_active_ref(struct i915_active *ref,
> - u64 timeline,
> + struct intel_timeline *tl,
> struct i915_request *rq);
>
> int i915_active_wait(struct i915_active *ref);
> diff --git a/drivers/gpu/drm/i915/i915_active_types.h b/drivers/gpu/drm/i915/i915_active_types.h
> index ae3ee441c114..d857bd12aa7e 100644
> --- a/drivers/gpu/drm/i915/i915_active_types.h
> +++ b/drivers/gpu/drm/i915/i915_active_types.h
> @@ -24,6 +24,9 @@ struct i915_active_request {
> struct i915_request __rcu *request;
> struct list_head link;
> i915_active_retire_fn retire;
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> + struct mutex *lock;

Checkpatch thinks the usage should be somehow stated with comment.

So put something like
/* Incorporeal. Ref piggypacking timeline for lockdep */

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> +#endif
> };
>
> struct active_node;
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index a32243951b29..73b02234affe 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -903,14 +903,14 @@ int i915_vma_move_to_active(struct i915_vma *vma,
> * add the active reference first and queue for it to be dropped
> * *last*.
> */
> - err = i915_active_ref(&vma->active, rq->fence.context, rq);
> + err = i915_active_ref(&vma->active, rq->timeline, rq);
> if (unlikely(err))
> return err;
>
> if (flags & EXEC_OBJECT_WRITE) {
> if (intel_frontbuffer_invalidate(obj->frontbuffer, ORIGIN_CS))
> i915_active_ref(&obj->frontbuffer->write,
> - rq->fence.context,
> + rq->timeline,
> rq);
>
> dma_resv_add_excl_fence(vma->resv, &rq->fence);
> diff --git a/drivers/gpu/drm/i915/selftests/i915_active.c b/drivers/gpu/drm/i915/selftests/i915_active.c
> index e5cd5d47e380..77d844ac8b71 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_active.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_active.c
> @@ -110,8 +110,7 @@ __live_active_setup(struct drm_i915_private *i915)
> submit,
> GFP_KERNEL);
> if (err >= 0)
> - err = i915_active_ref(&active->base,
> - rq->fence.context, rq);
> + err = i915_active_ref(&active->base, rq->timeline, rq);
> i915_request_add(rq);
> if (err) {
> pr_err("Failed to track active ref!\n");
> --
> 2.23.0.rc1