/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2019 Intel Corporation
*/
#include <linux/debugobjects.h>
#include "gt/intel_engine_pm.h"
#include "i915_drv.h"
#include "i915_active.h"
#include "i915_globals.h"
#define BKL(ref) (&(ref)->i915->drm.struct_mutex)
/*
* 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 i915_global_active {
struct i915_global base;
struct kmem_cache *slab_cache;
} global;
struct active_node {
struct i915_active_request base;
struct i915_active *ref;
struct rb_node node;
u64 timeline;
};
static inline struct active_node *
node_from_active(struct i915_active_request *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_request *active)
{
return IS_ERR(rcu_access_pointer(active->request));
}
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.link;
}
static inline struct intel_engine_cs *
__barrier_to_engine(struct active_node *node)
{
return (struct intel_engine_cs *)READ_ONCE(node->base.link.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.link);
}
#if IS_ENABLED([31mCONFIG_DRM_I915_DEBUG_GEM[0m) && IS_ENABLED([31mCONFIG_DEBUG_OBJECTS[0m)
static void *active_debug_hint(void *addr)
{
struct i915_active *ref = addr;
return (void *)ref->active ?: (void *)ref->retire ?: (void *)ref;
}
static 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)
{
debug_object_activate(ref, &active_debug_desc);
}
static void debug_active_deactivate(struct i915_active *ref)
{
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 active_node *it, *n;
struct rb_root root;
bool retire = false;
lockdep_assert_held(&ref->mutex);
/* return the unused nodes to our slabcache -- flushing the allocator */
if (atomic_dec_and_test(&ref->count)) {
debug_active_deactivate(ref);
root = ref->tree;
ref->tree = RB_ROOT;
ref->cache = NULL;
retire = true;
}
mutex_unlock(&ref->mutex);
if (!retire)
return;
rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
GEM_BUG_ON(i915_active_request_isset(&it->base));
kmem_cache_free(global.slab_cache, it);
}
/* After the final retire, the entire struct may be freed */
if (ref->retire)
ref->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;
/* One active may be flushed from inside the acquire of another */
mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING);
__active_retire(ref);
}
static void
node_retire(struct i915_active_request *base, struct i915_request *rq)
{
active_retire(node_from_active(base)->ref);
}
static struct i915_active_request *
active_instance(struct i915_active *ref, struct intel_timeline *tl)
{
struct active_node *node, *prealloc;
struct rb_node **p, *parent;
u64 idx = tl->fence_context;
/*
* 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.
*/
node = READ_ONCE(ref->cache);
if (node && node->timeline == idx)
return &node->base;
/* Preallocate a replacement, just in case */
prealloc = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
if (!prealloc)
return NULL;
mutex_lock(&ref->mutex);
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) {
kmem_cache_free(global.slab_cache, prealloc);
goto out;
}
if (node->timeline < idx)
p = &parent->rb_right;
else
p = &parent->rb_left;
}
node = prealloc;
i915_active_request_init(&node->base, &tl->mutex, NULL, node_retire);
node->ref = ref;
node->timeline = idx;
rb_link_node(&node->node, parent, p);
rb_insert_color(&node->node, &ref->tree);
out:
ref->cache = node;
mutex_unlock(&ref->mutex);
BUILD_BUG_ON(offsetof(typeof(*node), base));
return &node->base;
}
void __i915_active_init(struct drm_i915_private *i915,
struct i915_active *ref,
int (*active)(struct i915_active *ref),
void (*retire)(struct i915_active *ref),
struct lock_class_key *key)
{
debug_active_init(ref);
ref->i915 = i915;
ref->flags = 0;
ref->active = active;
ref->retire = retire;
ref->tree = RB_ROOT;
ref->cache = NULL;
init_llist_head(&ref->preallocated_barriers);
atomic_set(&ref->count, 0);
__mutex_init(&ref->mutex, "i915_active", key);
}
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));
}
int i915_active_ref(struct i915_active *ref,
struct intel_timeline *tl,
struct i915_request *rq)
{
struct i915_active_request *active;
int err;
lockdep_assert_held(&tl->mutex);
/* Prevent reaping in case we malloc/wait while building the tree */
err = i915_active_acquire(ref);
if (err)
return err;
active = active_instance(ref, tl);
if (!active) {
err = -ENOMEM;
goto out;
}
if (is_barrier(active)) { /* proto-node used by our idle barrier */
/*
* 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.
*/
__active_del_barrier(ref, node_from_active(active));
RCU_INIT_POINTER(active->request, NULL);
INIT_LIST_HEAD(&active->link);
} else {
if (!i915_active_request_isset(active))
atomic_inc(&ref->count);
}
GEM_BUG_ON(!atomic_read(&ref->count));
__i915_active_request_set(active, rq);
out:
i915_active_release(ref);
return err;
}
int i915_active_acquire(struct i915_active *ref)
{
int err;
debug_active_assert(ref);
if (atomic_add_unless(&ref->count, 1, 0))
return 0;
err = mutex_lock_interruptible(&ref->mutex);
if (err)
return err;
if (!atomic_read(&ref->count) && ref->active)
err = ref->active(ref);
if (!err) {
debug_active_activate(ref);
atomic_inc(&ref->count);
}
mutex_unlock(&ref->mutex);
return err;
}
void i915_active_release(struct i915_active *ref)
{
debug_active_assert(ref);
active_retire(ref);
}
static void __active_ungrab(struct i915_active *ref)
{
clear_and_wake_up_bit(I915_ACTIVE_GRAB_BIT, &ref->flags);
}
bool i915_active_trygrab(struct i915_active *ref)
{
debug_active_assert(ref);
if (test_and_set_bit(I915_ACTIVE_GRAB_BIT, &ref->flags))
return false;
if (!atomic_add_unless(&ref->count, 1, 0)) {
__active_ungrab(ref);
return false;
}
return true;
}
void i915_active_ungrab(struct i915_active *ref)
{
GEM_BUG_ON(!test_bit(I915_ACTIVE_GRAB_BIT, &ref->flags));
active_retire(ref);
__active_ungrab(ref);
}
int i915_active_wait(struct i915_active *ref)
{
struct active_node *it, *n;
int err;
might_sleep();
might_lock(&ref->mutex);
if (i915_active_is_idle(ref))
return 0;
err = mutex_lock_interruptible(&ref->mutex);
if (err)
return err;
if (!atomic_add_unless(&ref->count, 1, 0)) {
mutex_unlock(&ref->mutex);
return 0;
}
rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
if (is_barrier(&it->base)) { /* unconnected idle-barrier */
err = -EBUSY;
break;
}
err = i915_active_request_retire(&it->base, BKL(ref));
if (err)
break;
}
__active_retire(ref);
if (err)
return err;
if (wait_on_bit(&ref->flags, I915_ACTIVE_GRAB_BIT, TASK_KILLABLE))
return -EINTR;
if (!i915_active_is_idle(ref))
return -EBUSY;
return 0;
}
int i915_request_await_active_request(struct i915_request *rq,
struct i915_active_request *active)
{
struct i915_request *barrier =
i915_active_request_raw(active, &rq->i915->drm.struct_mutex);
return barrier ? i915_request_await_dma_fence(rq, &barrier->fence) : 0;
}
int i915_request_await_active(struct i915_request *rq, struct i915_active *ref)
{
struct active_node *it, *n;
int err;
if (RB_EMPTY_ROOT(&ref->tree))
return 0;
/* await allocates and so we need to avoid hitting the shrinker */
err = i915_active_acquire(ref);
if (err)
return err;
mutex_lock(&ref->mutex);
rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
err = i915_request_await_active_request(rq, &it->base);
if (err)
break;
}
mutex_unlock(&ref->mutex);
i915_active_release(ref);
return err;
}
#if IS_ENABLED([31mCONFIG_DRM_I915_DEBUG_GEM[0m)
void i915_active_fini(struct i915_active *ref)
{
debug_active_fini(ref);
GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
GEM_BUG_ON(atomic_read(&ref->count));
mutex_destroy(&ref->mutex);
}
#endif
static inline bool is_idle_barrier(struct active_node *node, u64 idx)
{
return node->timeline == idx && !i915_active_request_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;
mutex_lock(&ref->mutex);
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 = p->rb_right;
else
p = 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;
}
mutex_unlock(&ref->mutex);
return NULL;
match:
rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
if (p == &ref->cache->node)
ref->cache = NULL;
mutex_unlock(&ref->mutex);
return rb_entry(p, struct active_node, node);
}
int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
struct intel_engine_cs *engine)
{
struct drm_i915_private *i915 = engine->i915;
intel_engine_mask_t tmp, mask = engine->mask;
struct llist_node *pos, *next;
int err;
GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
/*
* 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()
*/
for_each_engine_masked(engine, i915, mask, tmp) {
u64 idx = engine->kernel_context->timeline->fence_context;
struct active_node *node;
node = reuse_idle_barrier(ref, idx);
if (!node) {
node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
if (!node) {
err = ENOMEM;
goto unwind;
}
#if IS_ENABLED([31mCONFIG_DRM_I915_DEBUG_GEM[0m)
node->base.lock =
&engine->kernel_context->timeline->mutex;
#endif
RCU_INIT_POINTER(node->base.request, NULL);
node->base.retire = node_retire;
node->timeline = idx;
node->ref = ref;
}
if (!i915_active_request_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.request, ERR_PTR(-EAGAIN));
node->base.link.prev = (void *)engine;
atomic_inc(&ref->count);
}
GEM_BUG_ON(barrier_to_engine(node) != engine);
llist_add(barrier_to_ll(node), &ref->preallocated_barriers);
intel_engine_pm_get(engine);
}
return 0;
unwind:
llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
struct active_node *node = barrier_from_ll(pos);
atomic_dec(&ref->count);
intel_engine_pm_put(barrier_to_engine(node));
kmem_cache_free(global.slab_cache, node);
}
return err;
}
void i915_active_acquire_barrier(struct i915_active *ref)
{
struct llist_node *pos, *next;
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.
*/
mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING);
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;
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);
llist_add(barrier_to_ll(node), &engine->barrier_tasks);
intel_engine_pm_put(engine);
}
mutex_unlock(&ref->mutex);
}
void i915_request_add_active_barriers(struct i915_request *rq)
{
struct intel_engine_cs *engine = rq->engine;
struct llist_node *node, *next;
GEM_BUG_ON(intel_engine_is_virtual(engine));
GEM_BUG_ON(rq->timeline != engine->kernel_context->timeline);
/*
* 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.
*/
llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks)) {
RCU_INIT_POINTER(barrier_from_ll(node)->base.request, rq);
smp_wmb(); /* serialise with reuse_idle_barrier */
list_add_tail((struct list_head *)node, &rq->active_list);
}
}
int i915_active_request_set(struct i915_active_request *active,
struct i915_request *rq)
{
int err;
#if IS_ENABLED([31mCONFIG_DRM_I915_DEBUG_GEM[0m)
lockdep_assert_held(active->lock);
#endif
/* Must maintain ordering wrt previous active requests */
err = i915_request_await_active_request(rq, active);
if (err)
return err;
__i915_active_request_set(active, rq);
return 0;
}
void i915_active_retire_noop(struct i915_active_request *active,
struct i915_request *request)
{
/* Space left intentionally blank */
}
#if IS_ENABLED([31mCONFIG_DRM_I915_SELFTEST[0m)
#include "selftests/i915_active.c"
#endif
static void i915_global_active_shrink(void)
{
kmem_cache_shrink(global.slab_cache);
}
static void i915_global_active_exit(void)
{
kmem_cache_destroy(global.slab_cache);
}
static struct i915_global_active global = { {
.shrink = i915_global_active_shrink,
.exit = i915_global_active_exit,
} };
int __init i915_global_active_init(void)
{
global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
if (!global.slab_cache)
return -ENOMEM;
i915_global_register(&global.base);
return 0;
}