/*
* 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;
}
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