drivers/gpu/drm/i915/i915_active.c - kernel/common - Git at Google

 /*
  * SPDX-License-Identifier: MIT
  *
  * Copyright © 2019 Intel Corporation
  */

 #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 void
 __active_park(struct i915_active *ref)
 {
 	struct active_node *it, *n;

 	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 		GEM_BUG_ON(i915_active_request_isset(&it->base));
 		kmem_cache_free(global.slab_cache, it);
 	}
 	ref->tree = RB_ROOT;
 }

 static void
 __active_retire(struct i915_active *ref)
 {
 	GEM_BUG_ON(!ref->count);
 	if (--ref->count)
 		return;

 	/* return the unused nodes to our slabcache */
 	__active_park(ref);

 	ref->retire(ref);
 }

 static void
 node_retire(struct i915_active_request *base, struct i915_request *rq)
 {
 	__active_retire(container_of(base, struct active_node, base)->ref);
 }

 static void
 last_retire(struct i915_active_request *base, struct i915_request *rq)
 {
 	__active_retire(container_of(base, struct i915_active, last));
 }

 static struct i915_active_request *
 active_instance(struct i915_active *ref, u64 idx)
 {
 	struct active_node *node;
 	struct rb_node **p, *parent;
 	struct i915_request *old;

 	/*
 	 * 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.
 	 *
 	 * Note that we allow the timeline to be active simultaneously in
 	 * the rbtree and the last cache. We do this to avoid having
 	 * to search and replace the rbtree element for a new timeline, with
 	 * the cost being that we must be aware that the ref may be retired
 	 * twice for the same timeline (as the older rbtree element will be
 	 * retired before the new request added to last).
 	 */
 	old = i915_active_request_raw(&ref->last, BKL(ref));
 	if (!old || old->fence.context == idx)
 		goto out;

 	/* Move the currently active fence into the rbtree */
 	idx = old->fence.context;

 	parent = NULL;
 	p = &ref->tree.rb_node;
 	while (*p) {
 		parent = *p;

 		node = rb_entry(parent, struct active_node, node);
 		if (node->timeline == idx)
 			goto replace;

 		if (node->timeline < idx)
 			p = &parent->rb_right;
 		else
 			p = &parent->rb_left;
 	}

 	node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);

 	/* kmalloc may retire the ref->last (thanks shrinker)! */
 	if (unlikely(!i915_active_request_raw(&ref->last, BKL(ref)))) {
 		kmem_cache_free(global.slab_cache, node);
 		goto out;
 	}

 	if (unlikely(!node))
 		return ERR_PTR(-ENOMEM);

 	i915_active_request_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);

 replace:
 	/*
 	 * Overwrite the previous active slot in the rbtree with last,
 	 * leaving last zeroed. If the previous slot is still active,
 	 * we must be careful as we now only expect to receive one retire
 	 * callback not two, and so much undo the active counting for the
 	 * overwritten slot.
 	 */
 	if (i915_active_request_isset(&node->base)) {
 		/* Retire ourselves from the old rq->active_list */
 		__list_del_entry(&node->base.link);
 		ref->count--;
 		GEM_BUG_ON(!ref->count);
 	}
 	GEM_BUG_ON(list_empty(&ref->last.link));
 	list_replace_init(&ref->last.link, &node->base.link);
 	node->base.request = fetch_and_zero(&ref->last.request);

 out:
 	return &ref->last;
 }

 void i915_active_init(struct drm_i915_private *i915,
 		      struct i915_active *ref,
 		      void (*retire)(struct i915_active *ref))
 {
 	ref->i915 = i915;
 	ref->retire = retire;
 	ref->tree = RB_ROOT;
 	i915_active_request_init(&ref->last, NULL, last_retire);
 	ref->count = 0;
 }

 int i915_active_ref(struct i915_active *ref,
 		    u64 timeline,
 		    struct i915_request *rq)
 {
 	struct i915_active_request *active;
 	int err = 0;

 	/* Prevent reaping in case we malloc/wait while building the tree */
 	i915_active_acquire(ref);

 	active = active_instance(ref, timeline);
 	if (IS_ERR(active)) {
 		err = PTR_ERR(active);
 		goto out;
 	}

 	if (!i915_active_request_isset(active))
 		ref->count++;
 	__i915_active_request_set(active, rq);

 	GEM_BUG_ON(!ref->count);
 out:
 	i915_active_release(ref);
 	return err;
 }

 bool i915_active_acquire(struct i915_active *ref)
 {
 	lockdep_assert_held(BKL(ref));
 	return !ref->count++;
 }

 void i915_active_release(struct i915_active *ref)
 {
 	lockdep_assert_held(BKL(ref));
 	__active_retire(ref);
 }

 int i915_active_wait(struct i915_active *ref)
 {
 	struct active_node *it, *n;
 	int ret = 0;

 	if (i915_active_acquire(ref))
 		goto out_release;

 	ret = i915_active_request_retire(&ref->last, BKL(ref));
 	if (ret)
 		goto out_release;

 	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 		ret = i915_active_request_retire(&it->base, BKL(ref));
 		if (ret)
 			break;
 	}

 out_release:
 	i915_active_release(ref);
 	return ret;
 }

 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 = 0;

 	/* await allocates and so we need to avoid hitting the shrinker */
 	if (i915_active_acquire(ref))
 		goto out; /* was idle */

 	err = i915_request_await_active_request(rq, &ref->last);
 	if (err)
 		goto out;

 	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 		err = i915_request_await_active_request(rq, &it->base);
 		if (err)
 			goto out;
 	}

 out:
 	i915_active_release(ref);
 	return err;
 }

 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
 void i915_active_fini(struct i915_active *ref)
 {
 	GEM_BUG_ON(i915_active_request_isset(&ref->last));
 	GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
 	GEM_BUG_ON(ref->count);
 }
 #endif

 int i915_active_request_set(struct i915_active_request *active,
 			    struct i915_request *rq)
 {
 	int err;

 	/* 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(CONFIG_DRM_I915_SELFTEST)
 #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;
 }
	/*
	* SPDX-License-Identifier: MIT
	*
	* Copyright © 2019 Intel Corporation
	*/

	#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 void
	__active_park(struct i915_active *ref)
	{
	struct active_node it, n;

	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
	GEM_BUG_ON(i915_active_request_isset(&it->base));
	kmem_cache_free(global.slab_cache, it);
	}
	ref->tree = RB_ROOT;
	}

	static void
	__active_retire(struct i915_active *ref)
	{
	GEM_BUG_ON(!ref->count);
	if (--ref->count)
	return;

	/* return the unused nodes to our slabcache */
	__active_park(ref);

	ref->retire(ref);
	}

	static void
	node_retire(struct i915_active_request base, struct i915_request rq)
	{
	__active_retire(container_of(base, struct active_node, base)->ref);
	}

	static void
	last_retire(struct i915_active_request base, struct i915_request rq)
	{
	__active_retire(container_of(base, struct i915_active, last));
	}

	static struct i915_active_request *
	active_instance(struct i915_active *ref, u64 idx)
	{
	struct active_node *node;
	struct rb_node *p, parent;
	struct i915_request *old;

	/*
	* 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.
	*
	* Note that we allow the timeline to be active simultaneously in
	* the rbtree and the last cache. We do this to avoid having
	* to search and replace the rbtree element for a new timeline, with
	* the cost being that we must be aware that the ref may be retired
	* twice for the same timeline (as the older rbtree element will be
	* retired before the new request added to last).
	*/
	old = i915_active_request_raw(&ref->last, BKL(ref));
	if (!old \|\| old->fence.context == idx)
	goto out;

	/* Move the currently active fence into the rbtree */
	idx = old->fence.context;

	parent = NULL;
	p = &ref->tree.rb_node;
	while (*p) {
	parent = *p;

	node = rb_entry(parent, struct active_node, node);
	if (node->timeline == idx)
	goto replace;

	if (node->timeline < idx)
	p = &parent->rb_right;
	else
	p = &parent->rb_left;
	}

	node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);

	/* kmalloc may retire the ref->last (thanks shrinker)! */
	if (unlikely(!i915_active_request_raw(&ref->last, BKL(ref)))) {
	kmem_cache_free(global.slab_cache, node);
	goto out;
	}

	if (unlikely(!node))
	return ERR_PTR(-ENOMEM);

	i915_active_request_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);

	replace:
	/*
	* Overwrite the previous active slot in the rbtree with last,
	* leaving last zeroed. If the previous slot is still active,
	* we must be careful as we now only expect to receive one retire
	* callback not two, and so much undo the active counting for the
	* overwritten slot.
	*/
	if (i915_active_request_isset(&node->base)) {
	/* Retire ourselves from the old rq->active_list */
	__list_del_entry(&node->base.link);
	ref->count--;
	GEM_BUG_ON(!ref->count);
	}
	GEM_BUG_ON(list_empty(&ref->last.link));
	list_replace_init(&ref->last.link, &node->base.link);
	node->base.request = fetch_and_zero(&ref->last.request);

	out:
	return &ref->last;
	}

	void i915_active_init(struct drm_i915_private *i915,
	struct i915_active *ref,
	void (retire)(struct i915_active ref))
	{
	ref->i915 = i915;
	ref->retire = retire;
	ref->tree = RB_ROOT;
	i915_active_request_init(&ref->last, NULL, last_retire);
	ref->count = 0;
	}

	int i915_active_ref(struct i915_active *ref,
	u64 timeline,
	struct i915_request *rq)
	{
	struct i915_active_request *active;
	int err = 0;

	/* Prevent reaping in case we malloc/wait while building the tree */
	i915_active_acquire(ref);

	active = active_instance(ref, timeline);
	if (IS_ERR(active)) {
	err = PTR_ERR(active);
	goto out;
	}

	if (!i915_active_request_isset(active))
	ref->count++;
	__i915_active_request_set(active, rq);

	GEM_BUG_ON(!ref->count);
	out:
	i915_active_release(ref);
	return err;
	}

	bool i915_active_acquire(struct i915_active *ref)
	{
	lockdep_assert_held(BKL(ref));
	return !ref->count++;
	}

	void i915_active_release(struct i915_active *ref)
	{
	lockdep_assert_held(BKL(ref));
	__active_retire(ref);
	}

	int i915_active_wait(struct i915_active *ref)
	{
	struct active_node it, n;
	int ret = 0;

	if (i915_active_acquire(ref))
	goto out_release;

	ret = i915_active_request_retire(&ref->last, BKL(ref));
	if (ret)
	goto out_release;

	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
	ret = i915_active_request_retire(&it->base, BKL(ref));
	if (ret)
	break;
	}

	out_release:
	i915_active_release(ref);
	return ret;
	}

	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 = 0;

	/* await allocates and so we need to avoid hitting the shrinker */
	if (i915_active_acquire(ref))
	goto out; /* was idle */

	err = i915_request_await_active_request(rq, &ref->last);
	if (err)
	goto out;

	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
	err = i915_request_await_active_request(rq, &it->base);
	if (err)
	goto out;
	}

	out:
	i915_active_release(ref);
	return err;
	}

	#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
	void i915_active_fini(struct i915_active *ref)
	{
	GEM_BUG_ON(i915_active_request_isset(&ref->last));
	GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
	GEM_BUG_ON(ref->count);
	}
	#endif

	int i915_active_request_set(struct i915_active_request *active,
	struct i915_request *rq)
	{
	int err;

	/* 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(CONFIG_DRM_I915_SELFTEST)
	#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;
	}