__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)
{
- i915_active_fence_cb(fence, cb);
- active_retire(container_of(cb, struct active_node, base.cb)->ref);
+ 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)
{
- i915_active_fence_cb(fence, cb);
- active_retire(container_of(cb, struct i915_active, excl.cb));
+ if (active_fence_cb(fence, cb))
+ active_retire(container_of(cb, struct i915_active, excl.cb));
}
static struct i915_active_fence *
}
node = prealloc;
- __i915_active_fence_init(&node->base, &tl->mutex, NULL, node_retire);
+ __i915_active_fence_init(&node->base, NULL, node_retire);
node->ref = ref;
node->timeline = idx;
init_llist_head(&ref->preallocated_barriers);
atomic_set(&ref->count, 0);
__mutex_init(&ref->mutex, "i915_active", key);
- __i915_active_fence_init(&ref->excl, &ref->mutex, NULL, excl_retire);
+ __i915_active_fence_init(&ref->excl, NULL, excl_retire);
INIT_WORK(&ref->work, active_work);
}
/* We expect the caller to manage the exclusive timeline ordering */
GEM_BUG_ON(i915_active_is_idle(ref));
- /*
- * As we don't know which mutex the caller is using, we told a small
- * lie to the debug code that it is using the i915_active.mutex;
- * and now we must stick to that lie.
- */
- mutex_acquire(&ref->mutex.dep_map, 0, 0, _THIS_IP_);
if (!__i915_active_fence_set(&ref->excl, f))
atomic_inc(&ref->count);
- mutex_release(&ref->mutex.dep_map, 0, _THIS_IP_);
}
bool i915_active_acquire_if_busy(struct i915_active *ref)
goto unwind;
}
-#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
- node->base.lock =
- &engine->kernel_context->timeline->mutex;
-#endif
RCU_INIT_POINTER(node->base.fence, NULL);
node->base.cb.func = node_retire;
node->timeline = idx;
node->base.cb.node.prev = (void *)engine;
atomic_inc(&ref->count);
}
+ GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
GEM_BUG_ON(barrier_to_engine(node) != engine);
llist_add(barrier_to_ll(node), &ref->preallocated_barriers);
}
}
+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;
*/
spin_lock_irqsave(&rq->lock, flags);
llist_for_each_safe(node, next, node) {
- RCU_INIT_POINTER(barrier_from_ll(node)->base.fence, &rq->fence);
- smp_wmb(); /* serialise with reuse_idle_barrier */
+ /* 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);
}
-#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
-#define active_is_held(active) lockdep_is_held((active)->lock)
-#else
-#define active_is_held(active) true
-#endif
-
/*
* __i915_active_fence_set: Update the last active fence along its timeline
* @active: the active tracker
* fence onto this one. Returns the previous fence (if not already completed),
* which the caller must ensure is executed before the new fence. To ensure
* that the order of fences within the timeline of the i915_active_fence is
- * maintained, it must be locked by the caller.
+ * understood, it should be locked by the caller.
*/
struct dma_fence *
__i915_active_fence_set(struct i915_active_fence *active,
struct dma_fence *prev;
unsigned long flags;
- /* NB: must be serialised by an outer timeline mutex (active->lock) */
- spin_lock_irqsave(fence->lock, flags);
+ if (fence == rcu_access_pointer(active->fence))
+ return fence;
+
GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
- prev = rcu_dereference_protected(active->fence, active_is_held(active));
+ /*
+ * Consider that we have two threads arriving (A and B), with
+ * C already resident as the active->fence.
+ *
+ * A does the xchg first, and so it sees C or NULL depending
+ * on the timing of the interrupt handler. If it is NULL, the
+ * previous fence must have been signaled and we know that
+ * we are first on the timeline. If it is still present,
+ * we acquire the lock on that fence and serialise with the interrupt
+ * handler, in the process 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.
+ *
+ * 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);
+ prev = xchg(__active_fence_slot(active), fence);
if (prev) {
GEM_BUG_ON(prev == fence);
spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
__list_del_entry(&active->cb.node);
spin_unlock(prev->lock); /* serialise with prev->cb_list */
-
- /*
- * active->fence is reset by the callback from inside
- * interrupt context. We need to serialise our list
- * manipulation with the fence->lock to prevent the prev
- * being lost inside an interrupt (it can't be replaced as
- * no other caller is allowed to enter __i915_active_fence_set
- * as we hold the timeline lock). After serialising with
- * the callback, we need to double check which ran first,
- * our list_del() [decoupling prev from the callback] or
- * the callback...
- */
- prev = rcu_access_pointer(active->fence);
}
-
- rcu_assign_pointer(active->fence, fence);
+ GEM_BUG_ON(rcu_access_pointer(active->fence) != fence);
list_add_tail(&active->cb.node, &fence->cb_list);
-
spin_unlock_irqrestore(fence->lock, flags);
return prev;
struct dma_fence *fence;
int err = 0;
-#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
- lockdep_assert_held(active->lock);
-#endif
-
/* Must maintain timeline ordering wrt previous active requests */
rcu_read_lock();
fence = __i915_active_fence_set(active, &rq->fence);
void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
{
- i915_active_fence_cb(fence, cb);
+ active_fence_cb(fence, cb);
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
projects / openwrt / staging / blogic.git / commitdiff