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25 #ifndef I915_GEM_REQUEST_H
26 #define I915_GEM_REQUEST_H
28 #include <linux/dma-fence.h>
31 #include "i915_sw_fence.h"
35 struct task_struct *tsk;
39 struct intel_signal_node {
41 struct intel_wait wait;
45 * Request queue structure.
47 * The request queue allows us to note sequence numbers that have been emitted
48 * and may be associated with active buffers to be retired.
50 * By keeping this list, we can avoid having to do questionable sequence
51 * number comparisons on buffer last_read|write_seqno. It also allows an
52 * emission time to be associated with the request for tracking how far ahead
53 * of the GPU the submission is.
55 * When modifying this structure be very aware that we perform a lockless
56 * RCU lookup of it that may race against reallocation of the struct
57 * from the slab freelist. We intentionally do not zero the structure on
58 * allocation so that the lookup can use the dangling pointers (and is
59 * cogniscent that those pointers may be wrong). Instead, everything that
60 * needs to be initialised must be done so explicitly.
62 * The requests are reference counted.
64 struct drm_i915_gem_request {
65 struct dma_fence fence;
68 /** On Which ring this request was generated */
69 struct drm_i915_private *i915;
72 * Context and ring buffer related to this request
73 * Contexts are refcounted, so when this request is associated with a
74 * context, we must increment the context's refcount, to guarantee that
75 * it persists while any request is linked to it. Requests themselves
76 * are also refcounted, so the request will only be freed when the last
77 * reference to it is dismissed, and the code in
78 * i915_gem_request_free() will then decrement the refcount on the
81 struct i915_gem_context *ctx;
82 struct intel_engine_cs *engine;
83 struct intel_ring *ring;
84 struct intel_signal_node signaling;
86 struct i915_sw_fence submit;
89 /** GEM sequence number associated with the previous request,
90 * when the HWS breadcrumb is equal to this the GPU is processing
95 /** Position in the ring of the start of the request */
99 * Position in the ring of the start of the postfix.
100 * This is required to calculate the maximum available ring space
101 * without overwriting the postfix.
105 /** Position in the ring of the end of the whole request */
108 /** Position in the ring of the end of any workarounds after the tail */
111 /** Preallocate space in the ring for the emitting the request */
115 * Context related to the previous request.
116 * As the contexts are accessed by the hardware until the switch is
117 * completed to a new context, the hardware may still be writing
118 * to the context object after the breadcrumb is visible. We must
119 * not unpin/unbind/prune that object whilst still active and so
120 * we keep the previous context pinned until the following (this)
121 * request is retired.
123 struct i915_gem_context *previous_context;
125 /** Batch buffer related to this request if any (used for
126 * error state dump only).
128 struct i915_vma *batch;
129 struct list_head active_list;
131 /** Time at which this request was emitted, in jiffies. */
132 unsigned long emitted_jiffies;
134 /** engine->request_list entry for this request */
135 struct list_head link;
137 /** ring->request_list entry for this request */
138 struct list_head ring_link;
140 struct drm_i915_file_private *file_priv;
141 /** file_priv list entry for this request */
142 struct list_head client_list;
144 /** Link in the execlist submission queue, guarded by execlist_lock. */
145 struct list_head execlist_link;
148 extern const struct dma_fence_ops i915_fence_ops;
150 static inline bool fence_is_i915(struct dma_fence *fence)
152 return fence->ops == &i915_fence_ops;
155 struct drm_i915_gem_request * __must_check
156 i915_gem_request_alloc(struct intel_engine_cs *engine,
157 struct i915_gem_context *ctx);
158 int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
159 struct drm_file *file);
160 void i915_gem_request_retire_upto(struct drm_i915_gem_request *req);
163 i915_gem_request_get_seqno(struct drm_i915_gem_request *req)
165 return req ? req->fence.seqno : 0;
168 static inline struct intel_engine_cs *
169 i915_gem_request_get_engine(struct drm_i915_gem_request *req)
171 return req ? req->engine : NULL;
174 static inline struct drm_i915_gem_request *
175 to_request(struct dma_fence *fence)
177 /* We assume that NULL fence/request are interoperable */
178 BUILD_BUG_ON(offsetof(struct drm_i915_gem_request, fence) != 0);
179 GEM_BUG_ON(fence && !fence_is_i915(fence));
180 return container_of(fence, struct drm_i915_gem_request, fence);
183 static inline struct drm_i915_gem_request *
184 i915_gem_request_get(struct drm_i915_gem_request *req)
186 return to_request(dma_fence_get(&req->fence));
189 static inline struct drm_i915_gem_request *
190 i915_gem_request_get_rcu(struct drm_i915_gem_request *req)
192 return to_request(dma_fence_get_rcu(&req->fence));
196 i915_gem_request_put(struct drm_i915_gem_request *req)
198 dma_fence_put(&req->fence);
201 static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst,
202 struct drm_i915_gem_request *src)
205 i915_gem_request_get(src);
208 i915_gem_request_put(*pdst);
214 i915_gem_request_await_object(struct drm_i915_gem_request *to,
215 struct drm_i915_gem_object *obj,
218 void __i915_add_request(struct drm_i915_gem_request *req, bool flush_caches);
219 #define i915_add_request(req) \
220 __i915_add_request(req, true)
221 #define i915_add_request_no_flush(req) \
222 __i915_add_request(req, false)
224 struct intel_rps_client;
225 #define NO_WAITBOOST ERR_PTR(-1)
226 #define IS_RPS_CLIENT(p) (!IS_ERR(p))
227 #define IS_RPS_USER(p) (!IS_ERR_OR_NULL(p))
229 int i915_wait_request(struct drm_i915_gem_request *req,
232 struct intel_rps_client *rps)
233 __attribute__((nonnull(1)));
234 #define I915_WAIT_INTERRUPTIBLE BIT(0)
235 #define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */
237 static inline u32 intel_engine_get_seqno(struct intel_engine_cs *engine);
240 * Returns true if seq1 is later than seq2.
242 static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
244 return (s32)(seq1 - seq2) >= 0;
248 i915_gem_request_started(const struct drm_i915_gem_request *req)
250 return i915_seqno_passed(intel_engine_get_seqno(req->engine),
251 req->previous_seqno);
255 i915_gem_request_completed(const struct drm_i915_gem_request *req)
257 return i915_seqno_passed(intel_engine_get_seqno(req->engine),
261 bool __i915_spin_request(const struct drm_i915_gem_request *request,
262 int state, unsigned long timeout_us);
263 static inline bool i915_spin_request(const struct drm_i915_gem_request *request,
264 int state, unsigned long timeout_us)
266 return (i915_gem_request_started(request) &&
267 __i915_spin_request(request, state, timeout_us));
270 /* We treat requests as fences. This is not be to confused with our
271 * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
272 * We use the fences to synchronize access from the CPU with activity on the
273 * GPU, for example, we should not rewrite an object's PTE whilst the GPU
274 * is reading them. We also track fences at a higher level to provide
275 * implicit synchronisation around GEM objects, e.g. set-domain will wait
276 * for outstanding GPU rendering before marking the object ready for CPU
277 * access, or a pageflip will wait until the GPU is complete before showing
278 * the frame on the scanout.
280 * In order to use a fence, the object must track the fence it needs to
281 * serialise with. For example, GEM objects want to track both read and
282 * write access so that we can perform concurrent read operations between
283 * the CPU and GPU engines, as well as waiting for all rendering to
284 * complete, or waiting for the last GPU user of a "fence register". The
285 * object then embeds a #i915_gem_active to track the most recent (in
286 * retirement order) request relevant for the desired mode of access.
287 * The #i915_gem_active is updated with i915_gem_active_set() to track the
288 * most recent fence request, typically this is done as part of
289 * i915_vma_move_to_active().
291 * When the #i915_gem_active completes (is retired), it will
292 * signal its completion to the owner through a callback as well as mark
293 * itself as idle (i915_gem_active.request == NULL). The owner
294 * can then perform any action, such as delayed freeing of an active
295 * resource including itself.
297 struct i915_gem_active;
299 typedef void (*i915_gem_retire_fn)(struct i915_gem_active *,
300 struct drm_i915_gem_request *);
302 struct i915_gem_active {
303 struct drm_i915_gem_request __rcu *request;
304 struct list_head link;
305 i915_gem_retire_fn retire;
308 void i915_gem_retire_noop(struct i915_gem_active *,
309 struct drm_i915_gem_request *request);
312 * init_request_active - prepares the activity tracker for use
313 * @active - the active tracker
314 * @func - a callback when then the tracker is retired (becomes idle),
317 * init_request_active() prepares the embedded @active struct for use as
318 * an activity tracker, that is for tracking the last known active request
319 * associated with it. When the last request becomes idle, when it is retired
320 * after completion, the optional callback @func is invoked.
323 init_request_active(struct i915_gem_active *active,
324 i915_gem_retire_fn retire)
326 INIT_LIST_HEAD(&active->link);
327 active->retire = retire ?: i915_gem_retire_noop;
331 * i915_gem_active_set - updates the tracker to watch the current request
332 * @active - the active tracker
333 * @request - the request to watch
335 * i915_gem_active_set() watches the given @request for completion. Whilst
336 * that @request is busy, the @active reports busy. When that @request is
337 * retired, the @active tracker is updated to report idle.
340 i915_gem_active_set(struct i915_gem_active *active,
341 struct drm_i915_gem_request *request)
343 list_move(&active->link, &request->active_list);
344 rcu_assign_pointer(active->request, request);
347 static inline struct drm_i915_gem_request *
348 __i915_gem_active_peek(const struct i915_gem_active *active)
350 /* Inside the error capture (running with the driver in an unknown
351 * state), we want to bend the rules slightly (a lot).
353 * Work is in progress to make it safer, in the meantime this keeps
354 * the known issue from spamming the logs.
356 return rcu_dereference_protected(active->request, 1);
360 * i915_gem_active_raw - return the active request
361 * @active - the active tracker
363 * i915_gem_active_raw() returns the current request being tracked, or NULL.
364 * It does not obtain a reference on the request for the caller, so the caller
365 * must hold struct_mutex.
367 static inline struct drm_i915_gem_request *
368 i915_gem_active_raw(const struct i915_gem_active *active, struct lock *mutex)
370 return rcu_dereference_protected(active->request,
371 lockdep_is_held(mutex));
375 * i915_gem_active_peek - report the active request being monitored
376 * @active - the active tracker
378 * i915_gem_active_peek() returns the current request being tracked if
379 * still active, or NULL. It does not obtain a reference on the request
380 * for the caller, so the caller must hold struct_mutex.
382 static inline struct drm_i915_gem_request *
383 i915_gem_active_peek(const struct i915_gem_active *active, struct lock *mutex)
385 struct drm_i915_gem_request *request;
387 request = i915_gem_active_raw(active, mutex);
388 if (!request || i915_gem_request_completed(request))
395 * i915_gem_active_get - return a reference to the active request
396 * @active - the active tracker
398 * i915_gem_active_get() returns a reference to the active request, or NULL
399 * if the active tracker is idle. The caller must hold struct_mutex.
401 static inline struct drm_i915_gem_request *
402 i915_gem_active_get(const struct i915_gem_active *active, struct lock *mutex)
404 return i915_gem_request_get(i915_gem_active_peek(active, mutex));
408 * __i915_gem_active_get_rcu - return a reference to the active request
409 * @active - the active tracker
411 * __i915_gem_active_get() returns a reference to the active request, or NULL
412 * if the active tracker is idle. The caller must hold the RCU read lock, but
413 * the returned pointer is safe to use outside of RCU.
415 static inline struct drm_i915_gem_request *
416 __i915_gem_active_get_rcu(const struct i915_gem_active *active)
418 /* Performing a lockless retrieval of the active request is super
419 * tricky. SLAB_DESTROY_BY_RCU merely guarantees that the backing
420 * slab of request objects will not be freed whilst we hold the
421 * RCU read lock. It does not guarantee that the request itself
422 * will not be freed and then *reused*. Viz,
426 * req = active.request
427 * retire(req) -> free(req);
428 * (req is now first on the slab freelist)
429 * active.request = NULL
431 * req = new submission on a new object
434 * To prevent the request from being reused whilst the caller
435 * uses it, we take a reference like normal. Whilst acquiring
436 * the reference we check that it is not in a destroyed state
437 * (refcnt == 0). That prevents the request being reallocated
438 * whilst the caller holds on to it. To check that the request
439 * was not reallocated as we acquired the reference we have to
440 * check that our request remains the active request across
441 * the lookup, in the same manner as a seqlock. The visibility
442 * of the pointer versus the reference counting is controlled
443 * by using RCU barriers (rcu_dereference and rcu_assign_pointer).
445 * In the middle of all that, we inspect whether the request is
446 * complete. Retiring is lazy so the request may be completed long
447 * before the active tracker is updated. Querying whether the
448 * request is complete is far cheaper (as it involves no locked
449 * instructions setting cachelines to exclusive) than acquiring
450 * the reference, so we do it first. The RCU read lock ensures the
451 * pointer dereference is valid, but does not ensure that the
452 * seqno nor HWS is the right one! However, if the request was
453 * reallocated, that means the active tracker's request was complete.
454 * If the new request is also complete, then both are and we can
455 * just report the active tracker is idle. If the new request is
456 * incomplete, then we acquire a reference on it and check that
457 * it remained the active request.
459 * It is then imperative that we do not zero the request on
460 * reallocation, so that we can chase the dangling pointers!
461 * See i915_gem_request_alloc().
464 struct drm_i915_gem_request *request;
466 request = rcu_dereference(active->request);
467 if (!request || i915_gem_request_completed(request))
470 /* An especially silly compiler could decide to recompute the
471 * result of i915_gem_request_completed, more specifically
472 * re-emit the load for request->fence.seqno. A race would catch
473 * a later seqno value, which could flip the result from true to
474 * false. Which means part of the instructions below might not
475 * be executed, while later on instructions are executed. Due to
476 * barriers within the refcounting the inconsistency can't reach
477 * past the call to i915_gem_request_get_rcu, but not executing
478 * that while still executing i915_gem_request_put() creates
479 * havoc enough. Prevent this with a compiler barrier.
483 request = i915_gem_request_get_rcu(request);
485 /* What stops the following rcu_access_pointer() from occurring
486 * before the above i915_gem_request_get_rcu()? If we were
487 * to read the value before pausing to get the reference to
488 * the request, we may not notice a change in the active
491 * The rcu_access_pointer() is a mere compiler barrier, which
492 * means both the CPU and compiler are free to perform the
493 * memory read without constraint. The compiler only has to
494 * ensure that any operations after the rcu_access_pointer()
495 * occur afterwards in program order. This means the read may
496 * be performed earlier by an out-of-order CPU, or adventurous
499 * The atomic operation at the heart of
500 * i915_gem_request_get_rcu(), see dma_fence_get_rcu(), is
501 * atomic_inc_not_zero() which is only a full memory barrier
502 * when successful. That is, if i915_gem_request_get_rcu()
503 * returns the request (and so with the reference counted
504 * incremented) then the following read for rcu_access_pointer()
505 * must occur after the atomic operation and so confirm
506 * that this request is the one currently being tracked.
508 * The corresponding write barrier is part of
509 * rcu_assign_pointer().
511 if (!request || request == rcu_access_pointer(active->request))
512 return rcu_pointer_handoff(request);
514 i915_gem_request_put(request);
519 * i915_gem_active_get_unlocked - return a reference to the active request
520 * @active - the active tracker
522 * i915_gem_active_get_unlocked() returns a reference to the active request,
523 * or NULL if the active tracker is idle. The reference is obtained under RCU,
524 * so no locking is required by the caller.
526 * The reference should be freed with i915_gem_request_put().
528 static inline struct drm_i915_gem_request *
529 i915_gem_active_get_unlocked(const struct i915_gem_active *active)
531 struct drm_i915_gem_request *request;
534 request = __i915_gem_active_get_rcu(active);
541 * i915_gem_active_isset - report whether the active tracker is assigned
542 * @active - the active tracker
544 * i915_gem_active_isset() returns true if the active tracker is currently
545 * assigned to a request. Due to the lazy retiring, that request may be idle
546 * and this may report stale information.
549 i915_gem_active_isset(const struct i915_gem_active *active)
551 return rcu_access_pointer(active->request);
555 * i915_gem_active_is_idle - report whether the active tracker is idle
556 * @active - the active tracker
558 * i915_gem_active_is_idle() returns true if the active tracker is currently
559 * unassigned or if the request is complete (but not yet retired). Requires
560 * the caller to hold struct_mutex (but that can be relaxed if desired).
563 i915_gem_active_is_idle(const struct i915_gem_active *active,
566 return !i915_gem_active_peek(active, mutex);
570 * i915_gem_active_wait - waits until the request is completed
571 * @active - the active request on which to wait
573 * i915_gem_active_wait() waits until the request is completed before
574 * returning. Note that it does not guarantee that the request is
575 * retired first, see i915_gem_active_retire().
577 * i915_gem_active_wait() returns immediately if the active
578 * request is already complete.
580 static inline int __must_check
581 i915_gem_active_wait(const struct i915_gem_active *active, struct lock *mutex)
583 struct drm_i915_gem_request *request;
585 request = i915_gem_active_peek(active, mutex);
589 return i915_wait_request(request,
590 I915_WAIT_INTERRUPTIBLE | I915_WAIT_LOCKED,
595 * i915_gem_active_wait_unlocked - waits until the request is completed
596 * @active - the active request on which to wait
597 * @flags - how to wait
598 * @timeout - how long to wait at most
599 * @rps - userspace client to charge for a waitboost
601 * i915_gem_active_wait_unlocked() waits until the request is completed before
602 * returning, without requiring any locks to be held. Note that it does not
603 * retire any requests before returning.
605 * This function relies on RCU in order to acquire the reference to the active
606 * request without holding any locks. See __i915_gem_active_get_rcu() for the
607 * glory details on how that is managed. Once the reference is acquired, we
608 * can then wait upon the request, and afterwards release our reference,
609 * free of any locking.
611 * This function wraps i915_wait_request(), see it for the full details on
614 * Returns 0 if successful, or a negative error code.
617 i915_gem_active_wait_unlocked(const struct i915_gem_active *active,
620 struct intel_rps_client *rps)
622 struct drm_i915_gem_request *request;
625 request = i915_gem_active_get_unlocked(active);
627 ret = i915_wait_request(request, flags, timeout, rps);
628 i915_gem_request_put(request);
635 * i915_gem_active_retire - waits until the request is retired
636 * @active - the active request on which to wait
638 * i915_gem_active_retire() waits until the request is completed,
639 * and then ensures that at least the retirement handler for this
640 * @active tracker is called before returning. If the @active
641 * tracker is idle, the function returns immediately.
643 static inline int __must_check
644 i915_gem_active_retire(struct i915_gem_active *active,
647 struct drm_i915_gem_request *request;
650 request = i915_gem_active_raw(active, mutex);
654 ret = i915_wait_request(request,
655 I915_WAIT_INTERRUPTIBLE | I915_WAIT_LOCKED,
660 list_del_init(&active->link);
661 RCU_INIT_POINTER(active->request, NULL);
663 active->retire(active, request);
668 /* Convenience functions for peeking at state inside active's request whilst
669 * guarded by the struct_mutex.
672 static inline uint32_t
673 i915_gem_active_get_seqno(const struct i915_gem_active *active,
676 return i915_gem_request_get_seqno(i915_gem_active_peek(active, mutex));
679 static inline struct intel_engine_cs *
680 i915_gem_active_get_engine(const struct i915_gem_active *active,
683 return i915_gem_request_get_engine(i915_gem_active_peek(active, mutex));
686 #define for_each_active(mask, idx) \
687 for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx))
689 #endif /* I915_GEM_REQUEST_H */