/* * Copyright © 2008-2018 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_REQUEST_H #define I915_REQUEST_H #include <linux/dma-fence.h> #include "i915_gem.h" #include "i915_scheduler.h" #include "i915_sw_fence.h" #include "i915_scheduler.h" #include <uapi/drm/i915_drm.h> struct drm_file; struct drm_i915_gem_object; struct i915_request; struct i915_timeline; struct intel_wait { struct rb_node node; struct task_struct *tsk; struct i915_request *request; u32 seqno; }; struct intel_signal_node { struct intel_wait wait; struct list_head link; }; struct i915_capture_list { struct i915_capture_list *next; struct i915_vma *vma; }; /** * 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 i915_request { struct dma_fence fence; spinlock_t lock; //struct spinlock 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_request_free() will then decrement the refcount on the * context. */ struct i915_gem_context *gem_context; struct intel_engine_cs *engine; struct intel_context *hw_context; struct intel_ring *ring; struct i915_timeline *timeline; struct intel_signal_node signaling; /* * The rcu epoch of when this request was allocated. Used to judiciously * apply backpressure on future allocations to ensure that under * mempressure there is sufficient RCU ticks for us to reclaim our * RCU protected slabs. */ unsigned long rcustate; /* * 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. */ struct i915_sw_fence submit; wait_queue_entry_t submitq; 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 * 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_sched_node sched; struct i915_dependency dep; /** * GEM sequence number associated with this request on the * global execution timeline. It is zero when the request is not * on the HW queue (i.e. not on the engine timeline list). * Its value is guarded by the timeline spinlock. */ u32 global_seqno; /** Position in the ring of the start of the request */ u32 head; /** Position in the ring of the start of the user packets */ u32 infix; /** * 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; /** Batch buffer related to this request if any (used for * error state dump only). */ struct i915_vma *batch; /** * Additional buffers requested by userspace to be captured upon * a GPU hang. The vma/obj on this list are protected by their * active reference - all objects on this list must also be * on the active_list (of their final request). */ struct i915_capture_list *capture_list; struct list_head active_list; /** Time at which this request was emitted, in jiffies. */ unsigned long emitted_jiffies; bool waitboost; /** 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_link; }; #define I915_FENCE_GFP (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN) 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 i915_request * __must_check i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx); void i915_request_retire_upto(struct i915_request *rq); static inline struct i915_request * to_request(struct dma_fence *fence) { /* We assume that NULL fence/request are interoperable */ BUILD_BUG_ON(offsetof(struct i915_request, fence) != 0); GEM_BUG_ON(fence && !dma_fence_is_i915(fence)); return container_of(fence, struct i915_request, fence); } static inline struct i915_request * i915_request_get(struct i915_request *rq) { return to_request(dma_fence_get(&rq->fence)); } static inline struct i915_request * i915_request_get_rcu(struct i915_request *rq) { return to_request(dma_fence_get_rcu(&rq->fence)); } static inline void i915_request_put(struct i915_request *rq) { dma_fence_put(&rq->fence); } /** * i915_request_global_seqno - report the current global seqno * @request - the request * * A request is assigned a global seqno only when it is on the hardware * execution queue. The global seqno can be used to maintain a list of * requests on the same engine in retirement order, for example for * constructing a priority queue for waiting. Prior to its execution, or * if it is subsequently removed in the event of preemption, its global * seqno is zero. As both insertion and removal from the execution queue * may operate in IRQ context, it is not guarded by the usual struct_mutex * BKL. Instead those relying on the global seqno must be prepared for its * value to change between reads. Only when the request is complete can * the global seqno be stable (due to the memory barriers on submitting * the commands to the hardware to write the breadcrumb, if the HWS shows * that it has passed the global seqno and the global seqno is unchanged * after the read, it is indeed complete). */ static u32 i915_request_global_seqno(const struct i915_request *request) { return READ_ONCE(request->global_seqno); } int i915_request_await_object(struct i915_request *to, struct drm_i915_gem_object *obj, bool write); int i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence); void i915_request_add(struct i915_request *rq); void __i915_request_submit(struct i915_request *request); void i915_request_submit(struct i915_request *request); void i915_request_skip(struct i915_request *request, int error); void __i915_request_unsubmit(struct i915_request *request); void i915_request_unsubmit(struct i915_request *request); long i915_request_wait(struct i915_request *rq, 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() */ #define I915_WAIT_FOR_IDLE_BOOST BIT(3) static inline bool intel_engine_has_started(struct intel_engine_cs *engine, u32 seqno); static inline bool intel_engine_has_completed(struct intel_engine_cs *engine, u32 seqno); /** * Returns true if seq1 is later than seq2. */ static inline bool i915_seqno_passed(u32 seq1, u32 seq2) { return (s32)(seq1 - seq2) >= 0; } /** * i915_request_started - check if the request has begun being executed * @rq: the request * * Returns true if the request has been submitted to hardware, and the hardware * has advanced passed the end of the previous request and so should be either * currently processing the request (though it may be preempted and so * not necessarily the next request to complete) or have completed the request. */ static inline bool i915_request_started(const struct i915_request *rq) { u32 seqno; seqno = i915_request_global_seqno(rq); if (!seqno) /* not yet submitted to HW */ return false; return intel_engine_has_started(rq->engine, seqno); } static inline bool __i915_request_completed(const struct i915_request *rq, u32 seqno) { GEM_BUG_ON(!seqno); return intel_engine_has_completed(rq->engine, seqno) && seqno == i915_request_global_seqno(rq); } static inline bool i915_request_completed(const struct i915_request *rq) { u32 seqno; seqno = i915_request_global_seqno(rq); if (!seqno) return false; return __i915_request_completed(rq, seqno); } static inline bool i915_sched_node_signaled(const struct i915_sched_node *node) { const struct i915_request *rq = container_of(node, const struct i915_request, sched); return i915_request_completed(rq); } void i915_retire_requests(struct drm_i915_private *i915); /* * 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 i915_request *); struct i915_gem_active { struct i915_request __rcu *request; struct list_head link; i915_gem_retire_fn retire; }; void i915_gem_retire_noop(struct i915_gem_active *, struct i915_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) { RCU_INIT_POINTER(active->request, NULL); 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 i915_request *request) { list_move(&active->link, &request->active_list); rcu_assign_pointer(active->request, request); } /** * i915_gem_active_set_retire_fn - updates the retirement callback * @active - the active tracker * @fn - the routine called when the request is retired * @mutex - struct_mutex used to guard retirements * * i915_gem_active_set_retire_fn() updates the function pointer that * is called when the final request associated with the @active tracker * is retired. */ static inline void i915_gem_active_set_retire_fn(struct i915_gem_active *active, i915_gem_retire_fn fn, struct lock *mutex) { lockdep_assert_held(mutex); active->retire = fn ?: i915_gem_retire_noop; } static inline struct i915_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 i915_request * i915_gem_active_raw(const struct i915_gem_active *active, struct lock *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 i915_request * i915_gem_active_peek(const struct i915_gem_active *active, struct lock *mutex) { struct i915_request *request; request = i915_gem_active_raw(active, mutex); if (!request || i915_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 i915_request * i915_gem_active_get(const struct i915_gem_active *active, struct lock *mutex) { return i915_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 i915_request * __i915_gem_active_get_rcu(const struct i915_gem_active *active) { /* * Performing a lockless retrieval of the active request is super * tricky. SLAB_TYPESAFE_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 * * rq = active.request * retire(rq) -> free(rq); * (rq is now first on the slab freelist) * active.request = NULL * * rq = new submission on a new object * ref(rq) * * 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_request_alloc(). */ do { struct i915_request *request; request = rcu_dereference(active->request); if (!request || i915_request_completed(request)) return NULL; /* * An especially silly compiler could decide to recompute the * result of i915_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_request_get_rcu, but not executing * that while still executing i915_request_put() creates * havoc enough. Prevent this with a compiler barrier. */ barrier(); request = i915_request_get_rcu(request); /* * What stops the following rcu_access_pointer() from occurring * before the above i915_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_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_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_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_request_put(). */ static inline struct i915_request * i915_gem_active_get_unlocked(const struct i915_gem_active *active) { struct i915_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_request_wait(), 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 i915_request *request; long ret = 0; request = i915_gem_active_get_unlocked(active); if (request) { ret = i915_request_wait(request, flags, MAX_SCHEDULE_TIMEOUT); i915_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 lock *mutex) { struct i915_request *request; long ret; request = i915_gem_active_raw(active, mutex); if (!request) return 0; ret = i915_request_wait(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_REQUEST_H */
