/* * Copyright © 2008-2015 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. * */ #ifndef I915_GEM_REQUEST_H #define I915_GEM_REQUEST_H #include #include "i915_gem.h" #include "i915_sw_fence.h" struct drm_file; struct drm_i915_gem_object; struct intel_wait { struct rb_node node; struct task_struct *tsk; u32 seqno; }; struct intel_signal_node { struct rb_node node; struct intel_wait wait; }; struct i915_dependency { struct i915_priotree *signaler; struct list_head signal_link; struct list_head wait_link; unsigned long flags; #define I915_DEPENDENCY_ALLOC BIT(0) }; /* Requests exist in a complex web of interdependencies. Each request * has to wait for some other request to complete before it is ready to be run * (e.g. we have to wait until the pixels have been rendering into a texture * before we can copy from it). We track the readiness of a request in terms * of fences, but we also need to keep the dependency tree for the lifetime * of the request (beyond the life of an individual fence). We use the tree * at various points to reorder the requests whilst keeping the requests * in order with respect to their various dependencies. */ struct i915_priotree { struct list_head signalers_list; /* those before us, we depend upon */ struct list_head waiters_list; /* those after us, they depend upon us */ }; /** * Request queue structure. * * The request queue allows us to note sequence numbers that have been emitted * and may be associated with active buffers to be retired. * * By keeping this list, we can avoid having to do questionable sequence * number comparisons on buffer last_read|write_seqno. It also allows an * emission time to be associated with the request for tracking how far ahead * of the GPU the submission is. * * When modifying this structure be very aware that we perform a lockless * RCU lookup of it that may race against reallocation of the struct * from the slab freelist. We intentionally do not zero the structure on * allocation so that the lookup can use the dangling pointers (and is * cogniscent that those pointers may be wrong). Instead, everything that * needs to be initialised must be done so explicitly. * * The requests are reference counted. */ struct drm_i915_gem_request { struct dma_fence fence; spinlock_t lock; /** On Which ring this request was generated */ struct drm_i915_private *i915; /** * Context and ring buffer related to this request * Contexts are refcounted, so when this request is associated with a * context, we must increment the context's refcount, to guarantee that * it persists while any request is linked to it. Requests themselves * are also refcounted, so the request will only be freed when the last * reference to it is dismissed, and the code in * i915_gem_request_free() will then decrement the refcount on the * context. */ struct i915_gem_context *ctx; struct intel_engine_cs *engine; struct intel_ring *ring; struct intel_timeline *timeline; struct intel_signal_node signaling; /* Fences for the various phases in the request's lifetime. * * 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; /* 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 * submit fence is signaled (it waits for all external events as well * as our own requests), the scheduler still needs to know the * dependency tree for the lifetime of the request (from execbuf * to retirement), i.e. bidirectional dependency information for the * request not tied to individual fences. */ struct i915_priotree priotree; struct i915_dependency dep; u32 global_seqno; /** GEM sequence number associated with the previous request, * when the HWS breadcrumb is equal to this the GPU is processing * this request. */ u32 previous_seqno; /** Position in the ring of the start of the request */ u32 head; /** * Position in the ring of the start of the postfix. * This is required to calculate the maximum available ring space * without overwriting the postfix. */ u32 postfix; /** Position in the ring of the end of the whole request */ u32 tail; /** Position in the ring of the end of any workarounds after the tail */ u32 wa_tail; /** Preallocate space in the ring for the emitting the request */ u32 reserved_space; /** * Context related to the previous request. * As the contexts are accessed by the hardware until the switch is * completed to a new context, the hardware may still be writing * to the context object after the breadcrumb is visible. We must * not unpin/unbind/prune that object whilst still active and so * we keep the previous context pinned until the following (this) * request is retired. */ struct i915_gem_context *previous_context; /** Batch buffer related to this request if any (used for * error state dump only). */ struct i915_vma *batch; struct list_head active_list; /** Time at which this request was emitted, in jiffies. */ unsigned long emitted_jiffies; /** engine->request_list entry for this request */ struct list_head link; /** ring->request_list entry for this request */ struct list_head ring_link; struct drm_i915_file_private *file_priv; /** file_priv list entry for this request */ struct list_head client_list; /** Link in the execlist submission queue, guarded by execlist_lock. */ struct list_head execlist_link; }; extern const struct dma_fence_ops i915_fence_ops; static inline bool dma_fence_is_i915(const struct dma_fence *fence) { return fence->ops == &i915_fence_ops; } struct drm_i915_gem_request * __must_check i915_gem_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx); int i915_gem_request_add_to_client(struct drm_i915_gem_request *req, struct drm_file *file); void i915_gem_request_retire_upto(struct drm_i915_gem_request *req); static inline struct drm_i915_gem_request * to_request(struct dma_fence *fence) { /* We assume that NULL fence/request are interoperable */ BUILD_BUG_ON(offsetof(struct drm_i915_gem_request, fence) != 0); GEM_BUG_ON(fence && !dma_fence_is_i915(fence)); return container_of(fence, struct drm_i915_gem_request, fence); } static inline struct drm_i915_gem_request * i915_gem_request_get(struct drm_i915_gem_request *req) { return to_request(dma_fence_get(&req->fence)); } static inline struct drm_i915_gem_request * i915_gem_request_get_rcu(struct drm_i915_gem_request *req) { return to_request(dma_fence_get_rcu(&req->fence)); } static inline void i915_gem_request_put(struct drm_i915_gem_request *req) { dma_fence_put(&req->fence); } static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, struct drm_i915_gem_request *src) { if (src) i915_gem_request_get(src); if (*pdst) i915_gem_request_put(*pdst); *pdst = src; } int i915_gem_request_await_object(struct drm_i915_gem_request *to, struct drm_i915_gem_object *obj, bool write); int i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req, struct dma_fence *fence); void __i915_add_request(struct drm_i915_gem_request *req, bool flush_caches); #define i915_add_request(req) \ __i915_add_request(req, true) #define i915_add_request_no_flush(req) \ __i915_add_request(req, false) void __i915_gem_request_submit(struct drm_i915_gem_request *request); void i915_gem_request_submit(struct drm_i915_gem_request *request); struct intel_rps_client; #define NO_WAITBOOST ERR_PTR(-1) #define IS_RPS_CLIENT(p) (!IS_ERR(p)) #define IS_RPS_USER(p) (!IS_ERR_OR_NULL(p)) long i915_wait_request(struct drm_i915_gem_request *req, unsigned int flags, long timeout) __attribute__((nonnull(1))); #define I915_WAIT_INTERRUPTIBLE BIT(0) #define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */ #define I915_WAIT_ALL BIT(2) /* used by i915_gem_object_wait() */ static inline u32 intel_engine_get_seqno(struct intel_engine_cs *engine); /** * Returns true if seq1 is later than seq2. */ static inline bool i915_seqno_passed(u32 seq1, u32 seq2) { return (s32)(seq1 - seq2) >= 0; } static inline bool __i915_gem_request_started(const struct drm_i915_gem_request *req) { GEM_BUG_ON(!req->global_seqno); return i915_seqno_passed(intel_engine_get_seqno(req->engine), req->previous_seqno); } static inline bool i915_gem_request_started(const struct drm_i915_gem_request *req) { if (!req->global_seqno) return false; return __i915_gem_request_started(req); } static inline bool __i915_gem_request_completed(const struct drm_i915_gem_request *req) { GEM_BUG_ON(!req->global_seqno); return i915_seqno_passed(intel_engine_get_seqno(req->engine), req->global_seqno); } static inline bool i915_gem_request_completed(const struct drm_i915_gem_request *req) { if (!req->global_seqno) return false; return __i915_gem_request_completed(req); } bool __i915_spin_request(const struct drm_i915_gem_request *request, int state, unsigned long timeout_us); static inline bool i915_spin_request(const struct drm_i915_gem_request *request, int state, unsigned long timeout_us) { return (__i915_gem_request_started(request) && __i915_spin_request(request, state, timeout_us)); } /* We treat requests as fences. This is not be to confused with our * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync. * We use the fences to synchronize access from the CPU with activity on the * GPU, for example, we should not rewrite an object's PTE whilst the GPU * is reading them. We also track fences at a higher level to provide * implicit synchronisation around GEM objects, e.g. set-domain will wait * for outstanding GPU rendering before marking the object ready for CPU * access, or a pageflip will wait until the GPU is complete before showing * the frame on the scanout. * * In order to use a fence, the object must track the fence it needs to * serialise with. For example, GEM objects want to track both read and * write access so that we can perform concurrent read operations between * the CPU and GPU engines, as well as waiting for all rendering to * complete, or waiting for the last GPU user of a "fence register". The * object then embeds a #i915_gem_active to track the most recent (in * retirement order) request relevant for the desired mode of access. * The #i915_gem_active is updated with i915_gem_active_set() to track the * most recent fence request, typically this is done as part of * i915_vma_move_to_active(). * * When the #i915_gem_active completes (is retired), it will * signal its completion to the owner through a callback as well as mark * itself as idle (i915_gem_active.request == NULL). The owner * can then perform any action, such as delayed freeing of an active * resource including itself. */ struct i915_gem_active; typedef void (*i915_gem_retire_fn)(struct i915_gem_active *, struct drm_i915_gem_request *); struct i915_gem_active { struct drm_i915_gem_request __rcu *request; struct list_head link; i915_gem_retire_fn retire; }; void i915_gem_retire_noop(struct i915_gem_active *, struct drm_i915_gem_request *request); /** * init_request_active - prepares the activity tracker for use * @active - the active tracker * @func - a callback when then the tracker is retired (becomes idle), * can be NULL * * init_request_active() prepares the embedded @active struct for use as * an activity tracker, that is for tracking the last known active request * associated with it. When the last request becomes idle, when it is retired * after completion, the optional callback @func is invoked. */ static inline void init_request_active(struct i915_gem_active *active, i915_gem_retire_fn retire) { INIT_LIST_HEAD(&active->link); active->retire = retire ?: i915_gem_retire_noop; } /** * i915_gem_active_set - updates the tracker to watch the current request * @active - the active tracker * @request - the request to watch * * i915_gem_active_set() watches the given @request for completion. Whilst * that @request is busy, the @active reports busy. When that @request is * retired, the @active tracker is updated to report idle. */ static inline void i915_gem_active_set(struct i915_gem_active *active, struct drm_i915_gem_request *request) { list_move(&active->link, &request->active_list); rcu_assign_pointer(active->request, request); } static inline struct drm_i915_gem_request * __i915_gem_active_peek(const struct i915_gem_active *active) { /* Inside the error capture (running with the driver in an unknown * state), we want to bend the rules slightly (a lot). * * Work is in progress to make it safer, in the meantime this keeps * the known issue from spamming the logs. */ return rcu_dereference_protected(active->request, 1); } /** * i915_gem_active_raw - return the active request * @active - the active tracker * * i915_gem_active_raw() returns the current request being tracked, or NULL. * It does not obtain a reference on the request for the caller, so the caller * must hold struct_mutex. */ static inline struct drm_i915_gem_request * i915_gem_active_raw(const struct i915_gem_active *active, struct mutex *mutex) { return rcu_dereference_protected(active->request, lockdep_is_held(mutex)); } /** * i915_gem_active_peek - report the active request being monitored * @active - the active tracker * * i915_gem_active_peek() returns the current request being tracked if * still active, or NULL. It does not obtain a reference on the request * for the caller, so the caller must hold struct_mutex. */ static inline struct drm_i915_gem_request * i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex) { struct drm_i915_gem_request *request; request = i915_gem_active_raw(active, mutex); if (!request || i915_gem_request_completed(request)) return NULL; return request; } /** * i915_gem_active_get - return a reference to the active request * @active - the active tracker * * i915_gem_active_get() returns a reference to the active request, or NULL * if the active tracker is idle. The caller must hold struct_mutex. */ static inline struct drm_i915_gem_request * i915_gem_active_get(const struct i915_gem_active *active, struct mutex *mutex) { return i915_gem_request_get(i915_gem_active_peek(active, mutex)); } /** * __i915_gem_active_get_rcu - return a reference to the active request * @active - the active tracker * * __i915_gem_active_get() returns a reference to the active request, or NULL * if the active tracker is idle. The caller must hold the RCU read lock, but * the returned pointer is safe to use outside of RCU. */ static inline struct drm_i915_gem_request * __i915_gem_active_get_rcu(const struct i915_gem_active *active) { /* Performing a lockless retrieval of the active request is super * tricky. SLAB_DESTROY_BY_RCU merely guarantees that the backing * slab of request objects will not be freed whilst we hold the * RCU read lock. It does not guarantee that the request itself * will not be freed and then *reused*. Viz, * * Thread A Thread B * * req = active.request * retire(req) -> free(req); * (req is now first on the slab freelist) * active.request = NULL * * req = new submission on a new object * ref(req) * * To prevent the request from being reused whilst the caller * uses it, we take a reference like normal. Whilst acquiring * the reference we check that it is not in a destroyed state * (refcnt == 0). That prevents the request being reallocated * whilst the caller holds on to it. To check that the request * was not reallocated as we acquired the reference we have to * check that our request remains the active request across * the lookup, in the same manner as a seqlock. The visibility * of the pointer versus the reference counting is controlled * by using RCU barriers (rcu_dereference and rcu_assign_pointer). * * In the middle of all that, we inspect whether the request is * complete. Retiring is lazy so the request may be completed long * before the active tracker is updated. Querying whether the * request is complete is far cheaper (as it involves no locked * instructions setting cachelines to exclusive) than acquiring * the reference, so we do it first. The RCU read lock ensures the * pointer dereference is valid, but does not ensure that the * seqno nor HWS is the right one! However, if the request was * reallocated, that means the active tracker's request was complete. * If the new request is also complete, then both are and we can * just report the active tracker is idle. If the new request is * incomplete, then we acquire a reference on it and check that * it remained the active request. * * It is then imperative that we do not zero the request on * reallocation, so that we can chase the dangling pointers! * See i915_gem_request_alloc(). */ do { struct drm_i915_gem_request *request; request = rcu_dereference(active->request); if (!request || i915_gem_request_completed(request)) return NULL; /* An especially silly compiler could decide to recompute the * result of i915_gem_request_completed, more specifically * re-emit the load for request->fence.seqno. A race would catch * a later seqno value, which could flip the result from true to * false. Which means part of the instructions below might not * be executed, while later on instructions are executed. Due to * barriers within the refcounting the inconsistency can't reach * past the call to i915_gem_request_get_rcu, but not executing * that while still executing i915_gem_request_put() creates * havoc enough. Prevent this with a compiler barrier. */ barrier(); request = i915_gem_request_get_rcu(request); /* What stops the following rcu_access_pointer() from occurring * before the above i915_gem_request_get_rcu()? If we were * to read the value before pausing to get the reference to * the request, we may not notice a change in the active * tracker. * * The rcu_access_pointer() is a mere compiler barrier, which * means both the CPU and compiler are free to perform the * memory read without constraint. The compiler only has to * ensure that any operations after the rcu_access_pointer() * occur afterwards in program order. This means the read may * be performed earlier by an out-of-order CPU, or adventurous * compiler. * * The atomic operation at the heart of * i915_gem_request_get_rcu(), see dma_fence_get_rcu(), is * atomic_inc_not_zero() which is only a full memory barrier * when successful. That is, if i915_gem_request_get_rcu() * returns the request (and so with the reference counted * incremented) then the following read for rcu_access_pointer() * must occur after the atomic operation and so confirm * that this request is the one currently being tracked. * * The corresponding write barrier is part of * rcu_assign_pointer(). */ if (!request || request == rcu_access_pointer(active->request)) return rcu_pointer_handoff(request); i915_gem_request_put(request); } while (1); } /** * i915_gem_active_get_unlocked - return a reference to the active request * @active - the active tracker * * i915_gem_active_get_unlocked() returns a reference to the active request, * or NULL if the active tracker is idle. The reference is obtained under RCU, * so no locking is required by the caller. * * The reference should be freed with i915_gem_request_put(). */ static inline struct drm_i915_gem_request * i915_gem_active_get_unlocked(const struct i915_gem_active *active) { struct drm_i915_gem_request *request; rcu_read_lock(); request = __i915_gem_active_get_rcu(active); rcu_read_unlock(); return request; } /** * i915_gem_active_isset - report whether the active tracker is assigned * @active - the active tracker * * i915_gem_active_isset() returns true if the active tracker is currently * assigned to a request. Due to the lazy retiring, that request may be idle * and this may report stale information. */ static inline bool i915_gem_active_isset(const struct i915_gem_active *active) { return rcu_access_pointer(active->request); } /** * i915_gem_active_wait - waits until the request is completed * @active - the active request on which to wait * @flags - how to wait * @timeout - how long to wait at most * @rps - userspace client to charge for a waitboost * * i915_gem_active_wait() waits until the request is completed before * returning, without requiring any locks to be held. Note that it does not * retire any requests before returning. * * This function relies on RCU in order to acquire the reference to the active * request without holding any locks. See __i915_gem_active_get_rcu() for the * glory details on how that is managed. Once the reference is acquired, we * can then wait upon the request, and afterwards release our reference, * free of any locking. * * This function wraps i915_wait_request(), see it for the full details on * the arguments. * * Returns 0 if successful, or a negative error code. */ static inline int i915_gem_active_wait(const struct i915_gem_active *active, unsigned int flags) { struct drm_i915_gem_request *request; long ret = 0; request = i915_gem_active_get_unlocked(active); if (request) { ret = i915_wait_request(request, flags, MAX_SCHEDULE_TIMEOUT); i915_gem_request_put(request); } return ret < 0 ? ret : 0; } /** * i915_gem_active_retire - waits until the request is retired * @active - the active request on which to wait * * i915_gem_active_retire() waits until the request is completed, * and then ensures that at least the retirement handler for this * @active tracker is called before returning. If the @active * tracker is idle, the function returns immediately. */ static inline int __must_check i915_gem_active_retire(struct i915_gem_active *active, struct mutex *mutex) { struct drm_i915_gem_request *request; long ret; request = i915_gem_active_raw(active, mutex); if (!request) return 0; ret = i915_wait_request(request, I915_WAIT_INTERRUPTIBLE | I915_WAIT_LOCKED, MAX_SCHEDULE_TIMEOUT); if (ret < 0) return ret; list_del_init(&active->link); RCU_INIT_POINTER(active->request, NULL); active->retire(active, request); return 0; } #define for_each_active(mask, idx) \ for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx)) #endif /* I915_GEM_REQUEST_H */