/* * SPDX-License-Identifier: MIT * * Copyright © 2019 Intel Corporation */ #include #include "gt/intel_context.h" #include "gt/intel_engine_heartbeat.h" #include "gt/intel_engine_pm.h" #include "gt/intel_ring.h" #include "i915_drv.h" #include "i915_active.h" /* * Active refs memory management * * To be more economical with memory, we reap all the i915_active trees as * they idle (when we know the active requests are inactive) and allocate the * nodes from a local slab cache to hopefully reduce the fragmentation. */ static struct pool slab_cache; struct active_node { struct rb_node node; struct i915_active_fence base; struct i915_active *ref; u64 timeline; }; #define fetch_node(x) rb_entry(READ_ONCE(x), typeof(struct active_node), node) static inline struct active_node * node_from_active(struct i915_active_fence *active) { return container_of(active, struct active_node, base); } #define take_preallocated_barriers(x) llist_del_all(&(x)->preallocated_barriers) static inline bool is_barrier(const struct i915_active_fence *active) { return IS_ERR(rcu_access_pointer(active->fence)); } static inline struct llist_node *barrier_to_ll(struct active_node *node) { GEM_BUG_ON(!is_barrier(&node->base)); return (struct llist_node *)&node->base.cb.node; } static inline struct intel_engine_cs * __barrier_to_engine(struct active_node *node) { return (struct intel_engine_cs *)READ_ONCE(node->base.cb.node.prev); } static inline struct intel_engine_cs * barrier_to_engine(struct active_node *node) { GEM_BUG_ON(!is_barrier(&node->base)); return __barrier_to_engine(node); } static inline struct active_node *barrier_from_ll(struct llist_node *x) { return container_of((struct list_head *)x, struct active_node, base.cb.node); } #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS) static void *active_debug_hint(void *addr) { struct i915_active *ref = addr; return (void *)ref->active ?: (void *)ref->retire ?: (void *)ref; } static const struct debug_obj_descr active_debug_desc = { .name = "i915_active", .debug_hint = active_debug_hint, }; static void debug_active_init(struct i915_active *ref) { debug_object_init(ref, &active_debug_desc); } static void debug_active_activate(struct i915_active *ref) { lockdep_assert_held(&ref->tree_lock); debug_object_activate(ref, &active_debug_desc); } static void debug_active_deactivate(struct i915_active *ref) { lockdep_assert_held(&ref->tree_lock); if (!atomic_read(&ref->count)) /* after the last dec */ debug_object_deactivate(ref, &active_debug_desc); } static void debug_active_fini(struct i915_active *ref) { debug_object_free(ref, &active_debug_desc); } static void debug_active_assert(struct i915_active *ref) { debug_object_assert_init(ref, &active_debug_desc); } #else static inline void debug_active_init(struct i915_active *ref) { } static inline void debug_active_activate(struct i915_active *ref) { } static inline void debug_active_deactivate(struct i915_active *ref) { } static inline void debug_active_fini(struct i915_active *ref) { } static inline void debug_active_assert(struct i915_active *ref) { } #endif static void __active_retire(struct i915_active *ref) { struct rb_root root = RB_ROOT; struct active_node *it, *n; unsigned long flags; GEM_BUG_ON(i915_active_is_idle(ref)); /* return the unused nodes to our slabcache -- flushing the allocator */ if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags)) return; GEM_BUG_ON(rcu_access_pointer(ref->excl.fence)); debug_active_deactivate(ref); /* Even if we have not used the cache, we may still have a barrier */ if (!ref->cache) ref->cache = fetch_node(ref->tree.rb_node); /* Keep the MRU cached node for reuse */ if (ref->cache) { /* Discard all other nodes in the tree */ rb_erase(&ref->cache->node, &ref->tree); root = ref->tree; /* Rebuild the tree with only the cached node */ rb_link_node(&ref->cache->node, NULL, &ref->tree.rb_node); rb_insert_color(&ref->cache->node, &ref->tree); GEM_BUG_ON(ref->tree.rb_node != &ref->cache->node); /* Make the cached node available for reuse with any timeline */ ref->cache->timeline = 0; /* needs cmpxchg(u64) */ } spin_unlock_irqrestore(&ref->tree_lock, flags); /* After the final retire, the entire struct may be freed */ if (ref->retire) ref->retire(ref); /* ... except if you wait on it, you must manage your own references! */ wake_up_var(ref); /* Finally free the discarded timeline tree */ rbtree_postorder_for_each_entry_safe(it, n, &root, node) { GEM_BUG_ON(i915_active_fence_isset(&it->base)); #ifdef __linux__ kmem_cache_free(slab_cache, it); #else pool_put(&slab_cache, it); #endif } } static void active_work(struct work_struct *wrk) { struct i915_active *ref = container_of(wrk, typeof(*ref), work); GEM_BUG_ON(!atomic_read(&ref->count)); if (atomic_add_unless(&ref->count, -1, 1)) return; __active_retire(ref); } static void active_retire(struct i915_active *ref) { GEM_BUG_ON(!atomic_read(&ref->count)); if (atomic_add_unless(&ref->count, -1, 1)) return; if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) { queue_work(system_unbound_wq, &ref->work); return; } __active_retire(ref); } static inline struct dma_fence ** __active_fence_slot(struct i915_active_fence *active) { return (struct dma_fence ** __force)&active->fence; } static inline bool active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb) { struct i915_active_fence *active = container_of(cb, typeof(*active), cb); return cmpxchg(__active_fence_slot(active), fence, NULL) == fence; } static void node_retire(struct dma_fence *fence, struct dma_fence_cb *cb) { if (active_fence_cb(fence, cb)) active_retire(container_of(cb, struct active_node, base.cb)->ref); } static void excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb) { if (active_fence_cb(fence, cb)) active_retire(container_of(cb, struct i915_active, excl.cb)); } static struct active_node *__active_lookup(struct i915_active *ref, u64 idx) { struct active_node *it; GEM_BUG_ON(idx == 0); /* 0 is the unordered timeline, rsvd for cache */ /* * We track the most recently used timeline to skip a rbtree search * for the common case, under typical loads we never need the rbtree * at all. We can reuse the last slot if it is empty, that is * after the previous activity has been retired, or if it matches the * current timeline. */ it = READ_ONCE(ref->cache); if (it) { u64 cached = READ_ONCE(it->timeline); /* Once claimed, this slot will only belong to this idx */ if (cached == idx) return it; /* * An unclaimed cache [.timeline=0] can only be claimed once. * * If the value is already non-zero, some other thread has * claimed the cache and we know that is does not match our * idx. If, and only if, the timeline is currently zero is it * worth competing to claim it atomically for ourselves (for * only the winner of that race will cmpxchg return the old * value of 0). */ if (!cached && !cmpxchg64(&it->timeline, 0, idx)) return it; } BUILD_BUG_ON(offsetof(typeof(*it), node)); /* While active, the tree can only be built; not destroyed */ GEM_BUG_ON(i915_active_is_idle(ref)); it = fetch_node(ref->tree.rb_node); while (it) { if (it->timeline < idx) { it = fetch_node(it->node.rb_right); } else if (it->timeline > idx) { it = fetch_node(it->node.rb_left); } else { WRITE_ONCE(ref->cache, it); break; } } /* NB: If the tree rotated beneath us, we may miss our target. */ return it; } static struct i915_active_fence * active_instance(struct i915_active *ref, u64 idx) { struct active_node *node; struct rb_node **p, *parent; node = __active_lookup(ref, idx); if (likely(node)) return &node->base; spin_lock_irq(&ref->tree_lock); GEM_BUG_ON(i915_active_is_idle(ref)); parent = NULL; p = &ref->tree.rb_node; while (*p) { parent = *p; node = rb_entry(parent, struct active_node, node); if (node->timeline == idx) goto out; if (node->timeline < idx) p = &parent->rb_right; else p = &parent->rb_left; } /* * XXX: We should preallocate this before i915_active_ref() is ever * called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC. */ #ifdef __linux__ node = kmem_cache_alloc(slab_cache, GFP_ATOMIC); #else node = pool_get(&slab_cache, PR_NOWAIT); #endif if (!node) goto out; __i915_active_fence_init(&node->base, NULL, node_retire); node->ref = ref; node->timeline = idx; rb_link_node(&node->node, parent, p); rb_insert_color(&node->node, &ref->tree); out: WRITE_ONCE(ref->cache, node); spin_unlock_irq(&ref->tree_lock); return &node->base; } void __i915_active_init(struct i915_active *ref, int (*active)(struct i915_active *ref), void (*retire)(struct i915_active *ref), unsigned long flags, struct lock_class_key *mkey, struct lock_class_key *wkey) { debug_active_init(ref); ref->flags = flags; ref->active = active; ref->retire = retire; mtx_init(&ref->tree_lock, IPL_TTY); ref->tree = RB_ROOT; ref->cache = NULL; init_llist_head(&ref->preallocated_barriers); atomic_set(&ref->count, 0); #ifdef __linux__ __mutex_init(&ref->mutex, "i915_active", mkey); #else rw_init(&ref->mutex, "i915_active"); #endif __i915_active_fence_init(&ref->excl, NULL, excl_retire); INIT_WORK(&ref->work, active_work); #if IS_ENABLED(CONFIG_LOCKDEP) lockdep_init_map(&ref->work.lockdep_map, "i915_active.work", wkey, 0); #endif } static bool ____active_del_barrier(struct i915_active *ref, struct active_node *node, struct intel_engine_cs *engine) { struct llist_node *head = NULL, *tail = NULL; struct llist_node *pos, *next; GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context); /* * Rebuild the llist excluding our node. We may perform this * outside of the kernel_context timeline mutex and so someone * else may be manipulating the engine->barrier_tasks, in * which case either we or they will be upset :) * * A second __active_del_barrier() will report failure to claim * the active_node and the caller will just shrug and know not to * claim ownership of its node. * * A concurrent i915_request_add_active_barriers() will miss adding * any of the tasks, but we will try again on the next -- and since * we are actively using the barrier, we know that there will be * at least another opportunity when we idle. */ llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) { if (node == barrier_from_ll(pos)) { node = NULL; continue; } pos->next = head; head = pos; if (!tail) tail = pos; } if (head) llist_add_batch(head, tail, &engine->barrier_tasks); return !node; } static bool __active_del_barrier(struct i915_active *ref, struct active_node *node) { return ____active_del_barrier(ref, node, barrier_to_engine(node)); } static bool replace_barrier(struct i915_active *ref, struct i915_active_fence *active) { if (!is_barrier(active)) /* proto-node used by our idle barrier? */ return false; /* * This request is on the kernel_context timeline, and so * we can use it to substitute for the pending idle-barrer * request that we want to emit on the kernel_context. */ return __active_del_barrier(ref, node_from_active(active)); } int i915_active_add_request(struct i915_active *ref, struct i915_request *rq) { u64 idx = i915_request_timeline(rq)->fence_context; struct dma_fence *fence = &rq->fence; struct i915_active_fence *active; int err; /* Prevent reaping in case we malloc/wait while building the tree */ err = i915_active_acquire(ref); if (err) return err; do { active = active_instance(ref, idx); if (!active) { err = -ENOMEM; goto out; } if (replace_barrier(ref, active)) { RCU_INIT_POINTER(active->fence, NULL); atomic_dec(&ref->count); } } while (unlikely(is_barrier(active))); fence = __i915_active_fence_set(active, fence); if (!fence) __i915_active_acquire(ref); else dma_fence_put(fence); out: i915_active_release(ref); return err; } static struct dma_fence * __i915_active_set_fence(struct i915_active *ref, struct i915_active_fence *active, struct dma_fence *fence) { struct dma_fence *prev; if (replace_barrier(ref, active)) { RCU_INIT_POINTER(active->fence, fence); return NULL; } prev = __i915_active_fence_set(active, fence); if (!prev) __i915_active_acquire(ref); return prev; } struct dma_fence * i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f) { /* We expect the caller to manage the exclusive timeline ordering */ return __i915_active_set_fence(ref, &ref->excl, f); } bool i915_active_acquire_if_busy(struct i915_active *ref) { debug_active_assert(ref); return atomic_add_unless(&ref->count, 1, 0); } static void __i915_active_activate(struct i915_active *ref) { spin_lock_irq(&ref->tree_lock); /* __active_retire() */ if (!atomic_fetch_inc(&ref->count)) debug_active_activate(ref); spin_unlock_irq(&ref->tree_lock); } int i915_active_acquire(struct i915_active *ref) { int err; if (i915_active_acquire_if_busy(ref)) return 0; if (!ref->active) { __i915_active_activate(ref); return 0; } err = mutex_lock_interruptible(&ref->mutex); if (err) return err; if (likely(!i915_active_acquire_if_busy(ref))) { err = ref->active(ref); if (!err) __i915_active_activate(ref); } mutex_unlock(&ref->mutex); return err; } int i915_active_acquire_for_context(struct i915_active *ref, u64 idx) { struct i915_active_fence *active; int err; err = i915_active_acquire(ref); if (err) return err; active = active_instance(ref, idx); if (!active) { i915_active_release(ref); return -ENOMEM; } return 0; /* return with active ref */ } void i915_active_release(struct i915_active *ref) { debug_active_assert(ref); active_retire(ref); } static void enable_signaling(struct i915_active_fence *active) { struct dma_fence *fence; if (unlikely(is_barrier(active))) return; fence = i915_active_fence_get(active); if (!fence) return; dma_fence_enable_sw_signaling(fence); dma_fence_put(fence); } static int flush_barrier(struct active_node *it) { struct intel_engine_cs *engine; if (likely(!is_barrier(&it->base))) return 0; engine = __barrier_to_engine(it); smp_rmb(); /* serialise with add_active_barriers */ if (!is_barrier(&it->base)) return 0; return intel_engine_flush_barriers(engine); } static int flush_lazy_signals(struct i915_active *ref) { struct active_node *it, *n; int err = 0; enable_signaling(&ref->excl); rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) { err = flush_barrier(it); /* unconnected idle barrier? */ if (err) break; enable_signaling(&it->base); } return err; } int __i915_active_wait(struct i915_active *ref, int state) { might_sleep(); /* Any fence added after the wait begins will not be auto-signaled */ if (i915_active_acquire_if_busy(ref)) { int err; err = flush_lazy_signals(ref); i915_active_release(ref); if (err) return err; if (___wait_var_event(ref, i915_active_is_idle(ref), state, 0, 0, schedule())) return -EINTR; } /* * After the wait is complete, the caller may free the active. * We have to flush any concurrent retirement before returning. */ flush_work(&ref->work); return 0; } static int __await_active(struct i915_active_fence *active, int (*fn)(void *arg, struct dma_fence *fence), void *arg) { struct dma_fence *fence; if (is_barrier(active)) /* XXX flush the barrier? */ return 0; fence = i915_active_fence_get(active); if (fence) { int err; err = fn(arg, fence); dma_fence_put(fence); if (err < 0) return err; } return 0; } struct wait_barrier { struct wait_queue_entry base; struct i915_active *ref; }; static int barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key) { struct wait_barrier *wb = container_of(wq, typeof(*wb), base); if (i915_active_is_idle(wb->ref)) { list_del(&wq->entry); i915_sw_fence_complete(wq->private); kfree(wq); } return 0; } static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence) { struct wait_barrier *wb; wb = kmalloc(sizeof(*wb), GFP_KERNEL); if (unlikely(!wb)) return -ENOMEM; GEM_BUG_ON(i915_active_is_idle(ref)); if (!i915_sw_fence_await(fence)) { kfree(wb); return -EINVAL; } wb->base.flags = 0; wb->base.func = barrier_wake; wb->base.private = fence; wb->ref = ref; add_wait_queue(__var_waitqueue(ref), &wb->base); return 0; } static int await_active(struct i915_active *ref, unsigned int flags, int (*fn)(void *arg, struct dma_fence *fence), void *arg, struct i915_sw_fence *barrier) { int err = 0; if (!i915_active_acquire_if_busy(ref)) return 0; if (flags & I915_ACTIVE_AWAIT_EXCL && rcu_access_pointer(ref->excl.fence)) { err = __await_active(&ref->excl, fn, arg); if (err) goto out; } if (flags & I915_ACTIVE_AWAIT_ACTIVE) { struct active_node *it, *n; rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) { err = __await_active(&it->base, fn, arg); if (err) goto out; } } if (flags & I915_ACTIVE_AWAIT_BARRIER) { err = flush_lazy_signals(ref); if (err) goto out; err = __await_barrier(ref, barrier); if (err) goto out; } out: i915_active_release(ref); return err; } static int rq_await_fence(void *arg, struct dma_fence *fence) { return i915_request_await_dma_fence(arg, fence); } int i915_request_await_active(struct i915_request *rq, struct i915_active *ref, unsigned int flags) { return await_active(ref, flags, rq_await_fence, rq, &rq->submit); } static int sw_await_fence(void *arg, struct dma_fence *fence) { return i915_sw_fence_await_dma_fence(arg, fence, 0, GFP_NOWAIT | __GFP_NOWARN); } int i915_sw_fence_await_active(struct i915_sw_fence *fence, struct i915_active *ref, unsigned int flags) { return await_active(ref, flags, sw_await_fence, fence, fence); } void i915_active_fini(struct i915_active *ref) { debug_active_fini(ref); GEM_BUG_ON(atomic_read(&ref->count)); GEM_BUG_ON(work_pending(&ref->work)); mutex_destroy(&ref->mutex); if (ref->cache) #ifdef __linux__ kmem_cache_free(slab_cache, ref->cache); #else pool_put(&slab_cache, ref->cache); #endif } static inline bool is_idle_barrier(struct active_node *node, u64 idx) { return node->timeline == idx && !i915_active_fence_isset(&node->base); } static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx) { struct rb_node *prev, *p; if (RB_EMPTY_ROOT(&ref->tree)) return NULL; GEM_BUG_ON(i915_active_is_idle(ref)); /* * Try to reuse any existing barrier nodes already allocated for this * i915_active, due to overlapping active phases there is likely a * node kept alive (as we reuse before parking). We prefer to reuse * completely idle barriers (less hassle in manipulating the llists), * but otherwise any will do. */ if (ref->cache && is_idle_barrier(ref->cache, idx)) { p = &ref->cache->node; goto match; } prev = NULL; p = ref->tree.rb_node; while (p) { struct active_node *node = rb_entry(p, struct active_node, node); if (is_idle_barrier(node, idx)) goto match; prev = p; if (node->timeline < idx) p = READ_ONCE(p->rb_right); else p = READ_ONCE(p->rb_left); } /* * No quick match, but we did find the leftmost rb_node for the * kernel_context. Walk the rb_tree in-order to see if there were * any idle-barriers on this timeline that we missed, or just use * the first pending barrier. */ for (p = prev; p; p = rb_next(p)) { struct active_node *node = rb_entry(p, struct active_node, node); struct intel_engine_cs *engine; if (node->timeline > idx) break; if (node->timeline < idx) continue; if (is_idle_barrier(node, idx)) goto match; /* * The list of pending barriers is protected by the * kernel_context timeline, which notably we do not hold * here. i915_request_add_active_barriers() may consume * the barrier before we claim it, so we have to check * for success. */ engine = __barrier_to_engine(node); smp_rmb(); /* serialise with add_active_barriers */ if (is_barrier(&node->base) && ____active_del_barrier(ref, node, engine)) goto match; } return NULL; match: spin_lock_irq(&ref->tree_lock); rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */ if (p == &ref->cache->node) WRITE_ONCE(ref->cache, NULL); spin_unlock_irq(&ref->tree_lock); return rb_entry(p, struct active_node, node); } int i915_active_acquire_preallocate_barrier(struct i915_active *ref, struct intel_engine_cs *engine) { intel_engine_mask_t tmp, mask = engine->mask; struct llist_node *first = NULL, *last = NULL; struct intel_gt *gt = engine->gt; GEM_BUG_ON(i915_active_is_idle(ref)); /* Wait until the previous preallocation is completed */ while (!llist_empty(&ref->preallocated_barriers)) cond_resched(); /* * Preallocate a node for each physical engine supporting the target * engine (remember virtual engines have more than one sibling). * We can then use the preallocated nodes in * i915_active_acquire_barrier() */ GEM_BUG_ON(!mask); for_each_engine_masked(engine, gt, mask, tmp) { u64 idx = engine->kernel_context->timeline->fence_context; struct llist_node *prev = first; struct active_node *node; rcu_read_lock(); node = reuse_idle_barrier(ref, idx); rcu_read_unlock(); if (!node) { #ifdef __linux__ node = kmem_cache_alloc(slab_cache, GFP_KERNEL); #else node = pool_get(&slab_cache, PR_WAITOK); #endif if (!node) goto unwind; RCU_INIT_POINTER(node->base.fence, NULL); node->base.cb.func = node_retire; node->timeline = idx; node->ref = ref; } if (!i915_active_fence_isset(&node->base)) { /* * Mark this as being *our* unconnected proto-node. * * Since this node is not in any list, and we have * decoupled it from the rbtree, we can reuse the * request to indicate this is an idle-barrier node * and then we can use the rb_node and list pointers * for our tracking of the pending barrier. */ RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN)); node->base.cb.node.prev = (void *)engine; __i915_active_acquire(ref); } GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN)); GEM_BUG_ON(barrier_to_engine(node) != engine); first = barrier_to_ll(node); first->next = prev; if (!last) last = first; intel_engine_pm_get(engine); } GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers)); llist_add_batch(first, last, &ref->preallocated_barriers); return 0; unwind: while (first) { struct active_node *node = barrier_from_ll(first); first = first->next; atomic_dec(&ref->count); intel_engine_pm_put(barrier_to_engine(node)); #ifdef __linux__ kmem_cache_free(slab_cache, node); #else pool_put(&slab_cache, node); #endif } return -ENOMEM; } void i915_active_acquire_barrier(struct i915_active *ref) { struct llist_node *pos, *next; unsigned long flags; GEM_BUG_ON(i915_active_is_idle(ref)); /* * Transfer the list of preallocated barriers into the * i915_active rbtree, but only as proto-nodes. They will be * populated by i915_request_add_active_barriers() to point to the * request that will eventually release them. */ llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) { struct active_node *node = barrier_from_ll(pos); struct intel_engine_cs *engine = barrier_to_engine(node); struct rb_node **p, *parent; spin_lock_irqsave_nested(&ref->tree_lock, flags, SINGLE_DEPTH_NESTING); parent = NULL; p = &ref->tree.rb_node; while (*p) { struct active_node *it; parent = *p; it = rb_entry(parent, struct active_node, node); if (it->timeline < node->timeline) p = &parent->rb_right; else p = &parent->rb_left; } rb_link_node(&node->node, parent, p); rb_insert_color(&node->node, &ref->tree); spin_unlock_irqrestore(&ref->tree_lock, flags); GEM_BUG_ON(!intel_engine_pm_is_awake(engine)); llist_add(barrier_to_ll(node), &engine->barrier_tasks); intel_engine_pm_put_delay(engine, 2); } } static struct dma_fence **ll_to_fence_slot(struct llist_node *node) { return __active_fence_slot(&barrier_from_ll(node)->base); } void i915_request_add_active_barriers(struct i915_request *rq) { struct intel_engine_cs *engine = rq->engine; struct llist_node *node, *next; unsigned long flags; GEM_BUG_ON(!intel_context_is_barrier(rq->context)); GEM_BUG_ON(intel_engine_is_virtual(engine)); GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline); node = llist_del_all(&engine->barrier_tasks); if (!node) return; /* * Attach the list of proto-fences to the in-flight request such * that the parent i915_active will be released when this request * is retired. */ spin_lock_irqsave(&rq->lock, flags); llist_for_each_safe(node, next, node) { /* serialise with reuse_idle_barrier */ smp_store_mb(*ll_to_fence_slot(node), &rq->fence); list_add_tail((struct list_head *)node, &rq->fence.cb_list); } spin_unlock_irqrestore(&rq->lock, flags); } /* * __i915_active_fence_set: Update the last active fence along its timeline * @active: the active tracker * @fence: the new fence (under construction) * * Records the new @fence as the last active fence along its timeline in * this active tracker, moving the tracking callbacks from the previous * fence onto this one. Gets and returns a reference to the previous fence * (if not already completed), which the caller must put after making sure * that it is executed before the new fence. To ensure that the order of * fences within the timeline of the i915_active_fence is understood, it * should be locked by the caller. */ struct dma_fence * __i915_active_fence_set(struct i915_active_fence *active, struct dma_fence *fence) { struct dma_fence *prev; unsigned long flags; /* * In case of fences embedded in i915_requests, their memory is * SLAB_FAILSAFE_BY_RCU, then it can be reused right after release * by new requests. Then, there is a risk of passing back a pointer * to a new, completely unrelated fence that reuses the same memory * while tracked under a different active tracker. Combined with i915 * perf open/close operations that build await dependencies between * engine kernel context requests and user requests from different * timelines, this can lead to dependency loops and infinite waits. * * As a countermeasure, we try to get a reference to the active->fence * first, so if we succeed and pass it back to our user then it is not * released and potentially reused by an unrelated request before the * user has a chance to set up an await dependency on it. */ prev = i915_active_fence_get(active); if (fence == prev) return fence; GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)); /* * Consider that we have two threads arriving (A and B), with * C already resident as the active->fence. * * Both A and B have got a reference to C or NULL, depending on the * timing of the interrupt handler. Let's assume that if A has got C * then it has locked C first (before B). * * Note the strong ordering of the timeline also provides consistent * nesting rules for the fence->lock; the inner lock is always the * older lock. */ spin_lock_irqsave(fence->lock, flags); if (prev) spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING); /* * A does the cmpxchg first, and so it sees C or NULL, as before, or * something else, depending on the timing of other threads and/or * interrupt handler. If not the same as before then A unlocks C if * applicable and retries, starting from an attempt to get a new * active->fence. Meanwhile, B follows the same path as A. * Once A succeeds with cmpxch, B fails again, retires, gets A from * active->fence, locks it as soon as A completes, and possibly * succeeds with cmpxchg. */ while (cmpxchg(__active_fence_slot(active), prev, fence) != prev) { if (prev) { spin_unlock(prev->lock); dma_fence_put(prev); } spin_unlock_irqrestore(fence->lock, flags); prev = i915_active_fence_get(active); GEM_BUG_ON(prev == fence); spin_lock_irqsave(fence->lock, flags); if (prev) spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING); } /* * If prev is NULL then the previous fence must have been signaled * and we know that we are first on the timeline. If it is still * present then, having the lock on that fence already acquired, we * serialise with the interrupt handler, in the process of removing it * from any future interrupt callback. A will then wait on C before * executing (if present). * * As B is second, it sees A as the previous fence and so waits for * it to complete its transition and takes over the occupancy for * itself -- remembering that it needs to wait on A before executing. */ if (prev) { __list_del_entry(&active->cb.node); spin_unlock(prev->lock); /* serialise with prev->cb_list */ } list_add_tail(&active->cb.node, &fence->cb_list); spin_unlock_irqrestore(fence->lock, flags); return prev; } int i915_active_fence_set(struct i915_active_fence *active, struct i915_request *rq) { struct dma_fence *fence; int err = 0; /* Must maintain timeline ordering wrt previous active requests */ fence = __i915_active_fence_set(active, &rq->fence); if (fence) { err = i915_request_await_dma_fence(rq, fence); dma_fence_put(fence); } return err; } void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb) { active_fence_cb(fence, cb); } struct auto_active { struct i915_active base; struct kref ref; }; struct i915_active *i915_active_get(struct i915_active *ref) { struct auto_active *aa = container_of(ref, typeof(*aa), base); kref_get(&aa->ref); return &aa->base; } static void auto_release(struct kref *ref) { struct auto_active *aa = container_of(ref, typeof(*aa), ref); i915_active_fini(&aa->base); kfree(aa); } void i915_active_put(struct i915_active *ref) { struct auto_active *aa = container_of(ref, typeof(*aa), base); kref_put(&aa->ref, auto_release); } static int auto_active(struct i915_active *ref) { i915_active_get(ref); return 0; } static void auto_retire(struct i915_active *ref) { i915_active_put(ref); } struct i915_active *i915_active_create(void) { struct auto_active *aa; aa = kmalloc(sizeof(*aa), GFP_KERNEL); if (!aa) return NULL; kref_init(&aa->ref); i915_active_init(&aa->base, auto_active, auto_retire, 0); return &aa->base; } #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) #include "selftests/i915_active.c" #endif void i915_active_module_exit(void) { #ifdef __linux__ kmem_cache_destroy(slab_cache); #else pool_destroy(&slab_cache); #endif } int __init i915_active_module_init(void) { #ifdef __linux__ slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN); if (!slab_cache) return -ENOMEM; #else pool_init(&slab_cache, sizeof(struct active_node), CACHELINESIZE, IPL_TTY, 0, "drmsc", NULL); #endif return 0; }