drm/i915: Deconstruct execute fence

On reflection, we are only using the execute fence as a waitqueue on the
global_seqno and not using it for dependency tracking between fences
(unlike the submit and dma fences). By only treating it as a waitqueue,
we can then treat it similar to the other waitqueues during submit,
making the code simpler.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170223074422.4125-8-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 34d4c12..37ef708 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -69,7 +69,6 @@ static void i915_fence_release(struct dma_fence *fence)
         * caught trying to reuse dead objects.
         */
        i915_sw_fence_fini(&req->submit);
-       i915_sw_fence_fini(&req->execute);
 
        kmem_cache_free(req->i915->requests, req);
 }
@@ -294,7 +293,6 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
 
        lockdep_assert_held(&request->i915->drm.struct_mutex);
        GEM_BUG_ON(!i915_sw_fence_signaled(&request->submit));
-       GEM_BUG_ON(!i915_sw_fence_signaled(&request->execute));
        GEM_BUG_ON(!i915_gem_request_completed(request));
        GEM_BUG_ON(!request->i915->gt.active_requests);
 
@@ -402,6 +400,8 @@ void __i915_gem_request_submit(struct drm_i915_gem_request *request)
        struct intel_timeline *timeline;
        u32 seqno;
 
+       trace_i915_gem_request_execute(request);
+
        /* Transfer from per-context onto the global per-engine timeline */
        timeline = engine->timeline;
        GEM_BUG_ON(timeline == request->timeline);
@@ -426,8 +426,7 @@ void __i915_gem_request_submit(struct drm_i915_gem_request *request)
        list_move_tail(&request->link, &timeline->requests);
        spin_unlock(&request->timeline->lock);
 
-       i915_sw_fence_commit(&request->execute);
-       trace_i915_gem_request_execute(request);
+       wake_up_all(&request->execute);
 }
 
 void i915_gem_request_submit(struct drm_i915_gem_request *request)
@@ -463,24 +462,6 @@ submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
        return NOTIFY_DONE;
 }
 
-static int __i915_sw_fence_call
-execute_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
-{
-       struct drm_i915_gem_request *request =
-               container_of(fence, typeof(*request), execute);
-
-       switch (state) {
-       case FENCE_COMPLETE:
-               break;
-
-       case FENCE_FREE:
-               i915_gem_request_put(request);
-               break;
-       }
-
-       return NOTIFY_DONE;
-}
-
 /**
  * i915_gem_request_alloc - allocate a request structure
  *
@@ -573,13 +554,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 
        /* We bump the ref for the fence chain */
        i915_sw_fence_init(&i915_gem_request_get(req)->submit, submit_notify);
-       i915_sw_fence_init(&i915_gem_request_get(req)->execute, execute_notify);
-
-       /* Ensure that the execute fence completes after the submit fence -
-        * as we complete the execute fence from within the submit fence
-        * callback, its completion would otherwise be visible first.
-        */
-       i915_sw_fence_await_sw_fence(&req->execute, &req->submit, &req->execq);
+       init_waitqueue_head(&req->execute);
 
        i915_priotree_init(&req->priotree);
 
@@ -1031,6 +1006,7 @@ long i915_wait_request(struct drm_i915_gem_request *req,
                TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
        wait_queue_head_t *errq = &req->i915->gpu_error.wait_queue;
        DEFINE_WAIT(reset);
+       DEFINE_WAIT(exec);
        struct intel_wait wait;
 
        might_sleep();
@@ -1052,12 +1028,11 @@ long i915_wait_request(struct drm_i915_gem_request *req,
        if (flags & I915_WAIT_LOCKED)
                add_wait_queue(errq, &reset);
 
-       if (!i915_sw_fence_done(&req->execute)) {
-               DEFINE_WAIT(exec);
-
+       reset_wait_queue(&req->execute, &exec);
+       if (!req->global_seqno) {
                do {
-                       prepare_to_wait(&req->execute.wait, &exec, state);
-                       if (i915_sw_fence_done(&req->execute))
+                       set_current_state(state);
+                       if (req->global_seqno)
                                break;
 
                        if (flags & I915_WAIT_LOCKED &&
@@ -1080,15 +1055,14 @@ long i915_wait_request(struct drm_i915_gem_request *req,
 
                        timeout = io_schedule_timeout(timeout);
                } while (1);
-               finish_wait(&req->execute.wait, &exec);
+               finish_wait(&req->execute, &exec);
 
                if (timeout < 0)
                        goto complete;
 
-               GEM_BUG_ON(!i915_sw_fence_done(&req->execute));
+               GEM_BUG_ON(!req->global_seqno);
        }
-       GEM_BUG_ON(!i915_sw_fence_done(&req->submit));
-       GEM_BUG_ON(!req->global_seqno);
+       GEM_BUG_ON(!i915_sw_fence_signaled(&req->submit));
 
        /* Optimistic short spin before touching IRQs */
        if (i915_spin_request(req, state, 5))

diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 9049936..467d3e1 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -119,18 +119,10 @@ struct drm_i915_gem_request {
         * The submit fence is used to await upon all of the request's
         * dependencies. When it is signaled, the request is ready to run.
         * It is used by the driver to then queue the request for execution.
-        *
-        * The execute fence is used to signal when the request has been
-        * sent to hardware.
-        *
-        * It is illegal for the submit fence of one request to wait upon the
-        * execute fence of an earlier request. It should be sufficient to
-        * wait upon the submit fence of the earlier request.
         */
        struct i915_sw_fence submit;
-       struct i915_sw_fence execute;
        wait_queue_t submitq;
-       wait_queue_t execq;
+       wait_queue_head_t execute;
 
        /* A list of everyone we wait upon, and everyone who waits upon us.
         * Even though we will not be submitted to the hardware before the