32  * retirement order) request relevant for the desired mode of access.
34  * track the most recent fence request, typically this is done as part of
39  * itself as idle (i915_active_request.request == NULL). The owner
45 			     struct i915_request *request);
50  * @rq - initial request to track, can be NULL
55  * an activity tracker, that is for tracking the last known active request
56  * associated with it. When the last request becomes idle, when it is retired
65 	RCU_INIT_POINTER(active->request, rq);  in i915_active_request_init()
77  * i915_active_request_set - updates the tracker to watch the current request
79  * @request - the request to watch
81  * __i915_active_request_set() watches the given @request for completion. Whilst
82  * that @request is busy, the @active reports busy. When that @request is
87 			  struct i915_request *request)  in __i915_active_request_set()  argument
92 	list_move(&active->link, &request->active_list);  in __i915_active_request_set()
93 	rcu_assign_pointer(active->request, request);  in __i915_active_request_set()
101  * i915_active_request_raw - return the active request
104  * i915_active_request_raw() returns the current request being tracked, or NULL.
105  * It does not obtain a reference on the request for the caller, so the caller
112 	return rcu_dereference_protected(active->request,  in i915_active_request_raw()
117  * i915_active_request_peek - report the active request being monitored
120  * i915_active_request_peek() returns the current request being tracked if
121  * still active, or NULL. It does not obtain a reference on the request
128 	struct i915_request *request;  in i915_active_request_peek()  local
130 	request = i915_active_request_raw(active, mutex);  in i915_active_request_peek()
131 	if (!request || i915_request_completed(request))  in i915_active_request_peek()
134 	return request;  in i915_active_request_peek()
138  * i915_active_request_get - return a reference to the active request
141  * i915_active_request_get() returns a reference to the active request, or NULL
152  * __i915_active_request_get_rcu - return a reference to the active request
155  * __i915_active_request_get() returns a reference to the active request,
163 	 * Performing a lockless retrieval of the active request is super  in __i915_active_request_get_rcu()
165 	 * slab of request objects will not be freed whilst we hold the  in __i915_active_request_get_rcu()
166 	 * RCU read lock. It does not guarantee that the request itself  in __i915_active_request_get_rcu()
171 	 * rq = active.request  in __i915_active_request_get_rcu()
174 	 *				active.request = NULL  in __i915_active_request_get_rcu()
179 	 * To prevent the request from being reused whilst the caller  in __i915_active_request_get_rcu()
182 	 * (refcnt == 0). That prevents the request being reallocated  in __i915_active_request_get_rcu()
183 	 * whilst the caller holds on to it. To check that the request  in __i915_active_request_get_rcu()
185 	 * check that our request remains the active request across  in __i915_active_request_get_rcu()
190 	 * In the middle of all that, we inspect whether the request is  in __i915_active_request_get_rcu()
191 	 * complete. Retiring is lazy so the request may be completed long  in __i915_active_request_get_rcu()
193 	 * request is complete is far cheaper (as it involves no locked  in __i915_active_request_get_rcu()
197 	 * seqno nor HWS is the right one! However, if the request was  in __i915_active_request_get_rcu()
198 	 * reallocated, that means the active tracker's request was complete.  in __i915_active_request_get_rcu()
199 	 * If the new request is also complete, then both are and we can  in __i915_active_request_get_rcu()
200 	 * just report the active tracker is idle. If the new request is  in __i915_active_request_get_rcu()
202 	 * it remained the active request.  in __i915_active_request_get_rcu()
204 	 * It is then imperative that we do not zero the request on  in __i915_active_request_get_rcu()
209 		struct i915_request *request;  in __i915_active_request_get_rcu()  local
211 		request = rcu_dereference(active->request);  in __i915_active_request_get_rcu()
212 		if (!request || i915_request_completed(request))  in __i915_active_request_get_rcu()
218 		 * re-emit the load for request->fence.seqno. A race would catch  in __i915_active_request_get_rcu()
229 		request = i915_request_get_rcu(request);  in __i915_active_request_get_rcu()
235 		 * the request, we may not notice a change in the active  in __i915_active_request_get_rcu()
250 		 * returns the request (and so with the reference counted  in __i915_active_request_get_rcu()
253 		 * that this request is the one currently being tracked.  in __i915_active_request_get_rcu()
258 		if (!request || request == rcu_access_pointer(active->request))  in __i915_active_request_get_rcu()
259 			return rcu_pointer_handoff(request);  in __i915_active_request_get_rcu()
261 		i915_request_put(request);  in __i915_active_request_get_rcu()
266  * i915_active_request_get_unlocked - return a reference to the active request
269  * i915_active_request_get_unlocked() returns a reference to the active request,
278 	struct i915_request *request;  in i915_active_request_get_unlocked()  local
281 	request = __i915_active_request_get_rcu(active);  in i915_active_request_get_unlocked()
284 	return request;  in i915_active_request_get_unlocked()
292  * assigned to a request. Due to the lazy retiring, that request may be idle
298 	return rcu_access_pointer(active->request);  in i915_active_request_isset()
302  * i915_active_request_retire - waits until the request is retired
303  * @active - the active request on which to wait
305  * i915_active_request_retire() waits until the request is completed,
314 	struct i915_request *request;  in i915_active_request_retire()  local
317 	request = i915_active_request_raw(active, mutex);  in i915_active_request_retire()
318 	if (!request)  in i915_active_request_retire()
321 	ret = i915_request_wait(request,  in i915_active_request_retire()
328 	RCU_INIT_POINTER(active->request, NULL);  in i915_active_request_retire()
330 	active->retire(active, request);  in i915_active_request_retire()
338  * Each set of commands submitted to the GPU compromises a single request that
346  * track every single request associated with the task, but knowing that
347  * each request belongs to an ordered timeline (later requests within a
349  * latest request in each timeline to determine the overall status of the
357  * provide a serialisation point either for request submission or for CPU