diff options
Diffstat (limited to 'drivers/gpu/drm/i915/i915_active.c')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_active.c | 1208 |
1 files changed, 1208 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c new file mode 100644 index 000000000..5ec293011 --- /dev/null +++ b/drivers/gpu/drm/i915/i915_active.c @@ -0,0 +1,1208 @@ +/* + * SPDX-License-Identifier: MIT + * + * Copyright © 2019 Intel Corporation + */ + +#include <linux/debugobjects.h> + +#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 kmem_cache *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)); + kmem_cache_free(slab_cache, it); + } +} + +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. + */ + node = kmem_cache_alloc(slab_cache, GFP_ATOMIC); + 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; + + spin_lock_init(&ref->tree_lock); + ref->tree = RB_ROOT; + ref->cache = NULL; + + init_llist_head(&ref->preallocated_barriers); + atomic_set(&ref->count, 0); + __mutex_init(&ref->mutex, "i915_active", mkey); + __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) + kmem_cache_free(slab_cache, ref->cache); +} + +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) { + node = kmem_cache_alloc(slab_cache, GFP_KERNEL); + 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)); + + kmem_cache_free(slab_cache, node); + } + 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) +{ + kmem_cache_destroy(slab_cache); +} + +int __init i915_active_module_init(void) +{ + slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN); + if (!slab_cache) + return -ENOMEM; + + return 0; +} |