drm/i915: Pull scheduling under standalone lock

Currently, the backend scheduling code abuses struct_mutex into order to
have a global lock to manipulate a temporary list (without widespread
allocation) and to protect against list modifications. This is an
extraneous coupling to struct_mutex and further can not extend beyond
the local device.

Pull all the code that needs to be under the one true lock into
i915_scheduler.c, and make it so.

Signed-off-by: Chris Wilson <[e-mail]>
Reviewed-by: Tvrtko Ursulin <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/Makefile

···
 	  i915_gemfs.o \
 	  i915_query.o \
 	  i915_request.o \
+	  i915_scheduler.o \
 	  i915_timeline.o \
 	  i915_trace_points.o \
 	  i915_vma.o \

drivers/gpu/drm/i915/i915_request.c

···
 	spin_unlock(&file_priv->mm.lock);
 }
 
-static struct i915_dependency *
-i915_dependency_alloc(struct drm_i915_private *i915)
-{
-	return kmem_cache_alloc(i915->dependencies, GFP_KERNEL);
-}
-
-static void
-i915_dependency_free(struct drm_i915_private *i915,
-		     struct i915_dependency *dep)
-{
-	kmem_cache_free(i915->dependencies, dep);
-}
-
-static void
-__i915_sched_node_add_dependency(struct i915_sched_node *node,
-				 struct i915_sched_node *signal,
-				 struct i915_dependency *dep,
-				 unsigned long flags)
-{
-	INIT_LIST_HEAD(&dep->dfs_link);
-	list_add(&dep->wait_link, &signal->waiters_list);
-	list_add(&dep->signal_link, &node->signalers_list);
-	dep->signaler = signal;
-	dep->flags = flags;
-}
-
-static int
-i915_sched_node_add_dependency(struct drm_i915_private *i915,
-			       struct i915_sched_node *node,
-			       struct i915_sched_node *signal)
-{
-	struct i915_dependency *dep;
-
-	dep = i915_dependency_alloc(i915);
-	if (!dep)
-		return -ENOMEM;
-
-	__i915_sched_node_add_dependency(node, signal, dep,
-					 I915_DEPENDENCY_ALLOC);
-	return 0;
-}
-
-static void
-i915_sched_node_fini(struct drm_i915_private *i915,
-		     struct i915_sched_node *node)
-{
-	struct i915_dependency *dep, *tmp;
-
-	GEM_BUG_ON(!list_empty(&node->link));
-
-	/*
-	 * Everyone we depended upon (the fences we wait to be signaled)
-	 * should retire before us and remove themselves from our list.
-	 * However, retirement is run independently on each timeline and
-	 * so we may be called out-of-order.
-	 */
-	list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) {
-		GEM_BUG_ON(!i915_sched_node_signaled(dep->signaler));
-		GEM_BUG_ON(!list_empty(&dep->dfs_link));
-
-		list_del(&dep->wait_link);
-		if (dep->flags & I915_DEPENDENCY_ALLOC)
-			i915_dependency_free(i915, dep);
-	}
-
-	/* Remove ourselves from everyone who depends upon us */
-	list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) {
-		GEM_BUG_ON(dep->signaler != node);
-		GEM_BUG_ON(!list_empty(&dep->dfs_link));
-
-		list_del(&dep->signal_link);
-		if (dep->flags & I915_DEPENDENCY_ALLOC)
-			i915_dependency_free(i915, dep);
-	}
-}
-
-static void
-i915_sched_node_init(struct i915_sched_node *node)
-{
-	INIT_LIST_HEAD(&node->signalers_list);
-	INIT_LIST_HEAD(&node->waiters_list);
-	INIT_LIST_HEAD(&node->link);
-	node->attr.priority = I915_PRIORITY_INVALID;
-}
-
 static int reset_all_global_seqno(struct drm_i915_private *i915, u32 seqno)
 {
 	struct intel_engine_cs *engine;

drivers/gpu/drm/i915/i915_request.h

···
 	return __i915_request_completed(rq, seqno);
 }
 
-static inline bool i915_sched_node_signaled(const struct i915_sched_node *node)
-{
-	const struct i915_request *rq =
-		container_of(node, const struct i915_request, sched);
-
-	return i915_request_completed(rq);
-}
-
 void i915_retire_requests(struct drm_i915_private *i915);
 
 /*

drivers/gpu/drm/i915/i915_scheduler.c

···
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018 Intel Corporation
+ */
+
+#include <linux/mutex.h>
+
+#include "i915_drv.h"
+#include "i915_request.h"
+#include "i915_scheduler.h"
+
+static DEFINE_SPINLOCK(schedule_lock);
+
+static const struct i915_request *
+node_to_request(const struct i915_sched_node *node)
+{
+	return container_of(node, const struct i915_request, sched);
+}
+
+static inline bool node_signaled(const struct i915_sched_node *node)
+{
+	return i915_request_completed(node_to_request(node));
+}
+
+void i915_sched_node_init(struct i915_sched_node *node)
+{
+	INIT_LIST_HEAD(&node->signalers_list);
+	INIT_LIST_HEAD(&node->waiters_list);
+	INIT_LIST_HEAD(&node->link);
+	node->attr.priority = I915_PRIORITY_INVALID;
+}
+
+static struct i915_dependency *
+i915_dependency_alloc(struct drm_i915_private *i915)
+{
+	return kmem_cache_alloc(i915->dependencies, GFP_KERNEL);
+}
+
+static void
+i915_dependency_free(struct drm_i915_private *i915,
+		     struct i915_dependency *dep)
+{
+	kmem_cache_free(i915->dependencies, dep);
+}
+
+bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
+				      struct i915_sched_node *signal,
+				      struct i915_dependency *dep,
+				      unsigned long flags)
+{
+	bool ret = false;
+
+	spin_lock(&schedule_lock);
+
+	if (!node_signaled(signal)) {
+		INIT_LIST_HEAD(&dep->dfs_link);
+		list_add(&dep->wait_link, &signal->waiters_list);
+		list_add(&dep->signal_link, &node->signalers_list);
+		dep->signaler = signal;
+		dep->flags = flags;
+
+		ret = true;
+	}
+
+	spin_unlock(&schedule_lock);
+
+	return ret;
+}
+
+int i915_sched_node_add_dependency(struct drm_i915_private *i915,
+				   struct i915_sched_node *node,
+				   struct i915_sched_node *signal)
+{
+	struct i915_dependency *dep;
+
+	dep = i915_dependency_alloc(i915);
+	if (!dep)
+		return -ENOMEM;
+
+	if (!__i915_sched_node_add_dependency(node, signal, dep,
+					      I915_DEPENDENCY_ALLOC))
+		i915_dependency_free(i915, dep);
+
+	return 0;
+}
+
+void i915_sched_node_fini(struct drm_i915_private *i915,
+			  struct i915_sched_node *node)
+{
+	struct i915_dependency *dep, *tmp;
+
+	GEM_BUG_ON(!list_empty(&node->link));
+
+	spin_lock(&schedule_lock);
+
+	/*
+	 * Everyone we depended upon (the fences we wait to be signaled)
+	 * should retire before us and remove themselves from our list.
+	 * However, retirement is run independently on each timeline and
+	 * so we may be called out-of-order.
+	 */
+	list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) {
+		GEM_BUG_ON(!node_signaled(dep->signaler));
+		GEM_BUG_ON(!list_empty(&dep->dfs_link));
+
+		list_del(&dep->wait_link);
+		if (dep->flags & I915_DEPENDENCY_ALLOC)
+			i915_dependency_free(i915, dep);
+	}
+
+	/* Remove ourselves from everyone who depends upon us */
+	list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) {
+		GEM_BUG_ON(dep->signaler != node);
+		GEM_BUG_ON(!list_empty(&dep->dfs_link));
+
+		list_del(&dep->signal_link);
+		if (dep->flags & I915_DEPENDENCY_ALLOC)
+			i915_dependency_free(i915, dep);
+	}
+
+	spin_unlock(&schedule_lock);
+}
+
+static inline struct i915_priolist *to_priolist(struct rb_node *rb)
+{
+	return rb_entry(rb, struct i915_priolist, node);
+}
+
+static void assert_priolists(struct intel_engine_execlists * const execlists,
+			     long queue_priority)
+{
+	struct rb_node *rb;
+	long last_prio, i;
+
+	if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
+		return;
+
+	GEM_BUG_ON(rb_first_cached(&execlists->queue) !=
+		   rb_first(&execlists->queue.rb_root));
+
+	last_prio = (queue_priority >> I915_USER_PRIORITY_SHIFT) + 1;
+	for (rb = rb_first_cached(&execlists->queue); rb; rb = rb_next(rb)) {
+		const struct i915_priolist *p = to_priolist(rb);
+
+		GEM_BUG_ON(p->priority >= last_prio);
+		last_prio = p->priority;
+
+		GEM_BUG_ON(!p->used);
+		for (i = 0; i < ARRAY_SIZE(p->requests); i++) {
+			if (list_empty(&p->requests[i]))
+				continue;
+
+			GEM_BUG_ON(!(p->used & BIT(i)));
+		}
+	}
+}
+
+struct list_head *
+i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio)
+{
+	struct intel_engine_execlists * const execlists = &engine->execlists;
+	struct i915_priolist *p;
+	struct rb_node **parent, *rb;
+	bool first = true;
+	int idx, i;
+
+	lockdep_assert_held(&engine->timeline.lock);
+	assert_priolists(execlists, INT_MAX);
+
+	/* buckets sorted from highest [in slot 0] to lowest priority */
+	idx = I915_PRIORITY_COUNT - (prio & I915_PRIORITY_MASK) - 1;
+	prio >>= I915_USER_PRIORITY_SHIFT;
+	if (unlikely(execlists->no_priolist))
+		prio = I915_PRIORITY_NORMAL;
+
+find_priolist:
+	/* most positive priority is scheduled first, equal priorities fifo */
+	rb = NULL;
+	parent = &execlists->queue.rb_root.rb_node;
+	while (*parent) {
+		rb = *parent;
+		p = to_priolist(rb);
+		if (prio > p->priority) {
+			parent = &rb->rb_left;
+		} else if (prio < p->priority) {
+			parent = &rb->rb_right;
+			first = false;
+		} else {
+			goto out;
+		}
+	}
+
+	if (prio == I915_PRIORITY_NORMAL) {
+		p = &execlists->default_priolist;
+	} else {
+		p = kmem_cache_alloc(engine->i915->priorities, GFP_ATOMIC);
+		/* Convert an allocation failure to a priority bump */
+		if (unlikely(!p)) {
+			prio = I915_PRIORITY_NORMAL; /* recurses just once */
+
+			/* To maintain ordering with all rendering, after an
+			 * allocation failure we have to disable all scheduling.
+			 * Requests will then be executed in fifo, and schedule
+			 * will ensure that dependencies are emitted in fifo.
+			 * There will be still some reordering with existing
+			 * requests, so if userspace lied about their
+			 * dependencies that reordering may be visible.
+			 */
+			execlists->no_priolist = true;
+			goto find_priolist;
+		}
+	}
+
+	p->priority = prio;
+	for (i = 0; i < ARRAY_SIZE(p->requests); i++)
+		INIT_LIST_HEAD(&p->requests[i]);
+	rb_link_node(&p->node, rb, parent);
+	rb_insert_color_cached(&p->node, &execlists->queue, first);
+	p->used = 0;
+
+out:
+	p->used |= BIT(idx);
+	return &p->requests[idx];
+}
+
+static struct intel_engine_cs *
+sched_lock_engine(struct i915_sched_node *node, struct intel_engine_cs *locked)
+{
+	struct intel_engine_cs *engine = node_to_request(node)->engine;
+
+	GEM_BUG_ON(!locked);
+
+	if (engine != locked) {
+		spin_unlock(&locked->timeline.lock);
+		spin_lock(&engine->timeline.lock);
+	}
+
+	return engine;
+}
+
+void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+{
+	struct list_head *uninitialized_var(pl);
+	struct intel_engine_cs *engine, *last;
+	struct i915_dependency *dep, *p;
+	struct i915_dependency stack;
+	const int prio = attr->priority;
+	LIST_HEAD(dfs);
+
+	GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
+
+	if (i915_request_completed(rq))
+		return;
+
+	if (prio <= READ_ONCE(rq->sched.attr.priority))
+		return;
+
+	/* Needed in order to use the temporary link inside i915_dependency */
+	spin_lock(&schedule_lock);
+
+	stack.signaler = &rq->sched;
+	list_add(&stack.dfs_link, &dfs);
+
+	/*
+	 * Recursively bump all dependent priorities to match the new request.
+	 *
+	 * A naive approach would be to use recursion:
+	 * static void update_priorities(struct i915_sched_node *node, prio) {
+	 *	list_for_each_entry(dep, &node->signalers_list, signal_link)
+	 *		update_priorities(dep->signal, prio)
+	 *	queue_request(node);
+	 * }
+	 * but that may have unlimited recursion depth and so runs a very
+	 * real risk of overunning the kernel stack. Instead, we build
+	 * a flat list of all dependencies starting with the current request.
+	 * As we walk the list of dependencies, we add all of its dependencies
+	 * to the end of the list (this may include an already visited
+	 * request) and continue to walk onwards onto the new dependencies. The
+	 * end result is a topological list of requests in reverse order, the
+	 * last element in the list is the request we must execute first.
+	 */
+	list_for_each_entry(dep, &dfs, dfs_link) {
+		struct i915_sched_node *node = dep->signaler;
+
+		/*
+		 * Within an engine, there can be no cycle, but we may
+		 * refer to the same dependency chain multiple times
+		 * (redundant dependencies are not eliminated) and across
+		 * engines.
+		 */
+		list_for_each_entry(p, &node->signalers_list, signal_link) {
+			GEM_BUG_ON(p == dep); /* no cycles! */
+
+			if (node_signaled(p->signaler))
+				continue;
+
+			GEM_BUG_ON(p->signaler->attr.priority < node->attr.priority);
+			if (prio > READ_ONCE(p->signaler->attr.priority))
+				list_move_tail(&p->dfs_link, &dfs);
+		}
+	}
+
+	/*
+	 * If we didn't need to bump any existing priorities, and we haven't
+	 * yet submitted this request (i.e. there is no potential race with
+	 * execlists_submit_request()), we can set our own priority and skip
+	 * acquiring the engine locks.
+	 */
+	if (rq->sched.attr.priority == I915_PRIORITY_INVALID) {
+		GEM_BUG_ON(!list_empty(&rq->sched.link));
+		rq->sched.attr = *attr;
+
+		if (stack.dfs_link.next == stack.dfs_link.prev)
+			goto out_unlock;
+
+		__list_del_entry(&stack.dfs_link);
+	}
+
+	last = NULL;
+	engine = rq->engine;
+	spin_lock_irq(&engine->timeline.lock);
+
+	/* Fifo and depth-first replacement ensure our deps execute before us */
+	list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {
+		struct i915_sched_node *node = dep->signaler;
+
+		INIT_LIST_HEAD(&dep->dfs_link);
+
+		engine = sched_lock_engine(node, engine);
+
+		/* Recheck after acquiring the engine->timeline.lock */
+		if (prio <= node->attr.priority || node_signaled(node))
+			continue;
+
+		node->attr.priority = prio;
+		if (!list_empty(&node->link)) {
+			if (last != engine) {
+				pl = i915_sched_lookup_priolist(engine, prio);
+				last = engine;
+			}
+			list_move_tail(&node->link, pl);
+		} else {
+			/*
+			 * If the request is not in the priolist queue because
+			 * it is not yet runnable, then it doesn't contribute
+			 * to our preemption decisions. On the other hand,
+			 * if the request is on the HW, it too is not in the
+			 * queue; but in that case we may still need to reorder
+			 * the inflight requests.
+			 */
+			if (!i915_sw_fence_done(&node_to_request(node)->submit))
+				continue;
+		}
+
+		if (prio <= engine->execlists.queue_priority)
+			continue;
+
+		/*
+		 * If we are already the currently executing context, don't
+		 * bother evaluating if we should preempt ourselves.
+		 */
+		if (node_to_request(node)->global_seqno &&
+		    i915_seqno_passed(port_request(engine->execlists.port)->global_seqno,
+				      node_to_request(node)->global_seqno))
+			continue;
+
+		/* Defer (tasklet) submission until after all of our updates. */
+		engine->execlists.queue_priority = prio;
+		tasklet_hi_schedule(&engine->execlists.tasklet);
+	}
+
+	spin_unlock_irq(&engine->timeline.lock);
+
+out_unlock:
+	spin_unlock(&schedule_lock);
+}

drivers/gpu/drm/i915/i915_scheduler.h

···
 #define _I915_SCHEDULER_H_
 
 #include <linux/bitops.h>
+#include <linux/kernel.h>
 
 #include <uapi/drm/i915_drm.h>
+
+struct drm_i915_private;
+struct i915_request;
+struct intel_engine_cs;
 
 enum {
 	I915_PRIORITY_MIN = I915_CONTEXT_MIN_USER_PRIORITY - 1,
···
 	unsigned long flags;
 #define I915_DEPENDENCY_ALLOC BIT(0)
 };
+
+void i915_sched_node_init(struct i915_sched_node *node);
+
+bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
+				      struct i915_sched_node *signal,
+				      struct i915_dependency *dep,
+				      unsigned long flags);
+
+int i915_sched_node_add_dependency(struct drm_i915_private *i915,
+				   struct i915_sched_node *node,
+				   struct i915_sched_node *signal);
+
+void i915_sched_node_fini(struct drm_i915_private *i915,
+			  struct i915_sched_node *node);
+
+void i915_schedule(struct i915_request *request,
+		   const struct i915_sched_attr *attr);
+
+struct list_head *
+i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio);
 
 #endif /* _I915_SCHEDULER_H_ */

drivers/gpu/drm/i915/intel_display.c

···
 
 	ret = intel_plane_pin_fb(to_intel_plane_state(new_state));
 
-	fb_obj_bump_render_priority(obj);
-
 	mutex_unlock(&dev_priv->drm.struct_mutex);
 	i915_gem_object_unpin_pages(obj);
 	if (ret)
 		return ret;
 
+	fb_obj_bump_render_priority(obj);
 	intel_fb_obj_flush(obj, ORIGIN_DIRTYFB);
 
 	if (!new_state->fence) { /* implicit fencing */

drivers/gpu/drm/i915/intel_lrc.c

···
 	ce->lrc_desc = desc;
 }
 
-static void assert_priolists(struct intel_engine_execlists * const execlists,
-			     long queue_priority)
-{
-	struct rb_node *rb;
-	long last_prio, i;
-
-	if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
-		return;
-
-	GEM_BUG_ON(rb_first_cached(&execlists->queue) !=
-		   rb_first(&execlists->queue.rb_root));
-
-	last_prio = (queue_priority >> I915_USER_PRIORITY_SHIFT) + 1;
-	for (rb = rb_first_cached(&execlists->queue); rb; rb = rb_next(rb)) {
-		struct i915_priolist *p = to_priolist(rb);
-
-		GEM_BUG_ON(p->priority >= last_prio);
-		last_prio = p->priority;
-
-		GEM_BUG_ON(!p->used);
-		for (i = 0; i < ARRAY_SIZE(p->requests); i++) {
-			if (list_empty(&p->requests[i]))
-				continue;
-
-			GEM_BUG_ON(!(p->used & BIT(i)));
-		}
-	}
-}
-
-static struct list_head *
-lookup_priolist(struct intel_engine_cs *engine, int prio)
-{
-	struct intel_engine_execlists * const execlists = &engine->execlists;
-	struct i915_priolist *p;
-	struct rb_node **parent, *rb;
-	bool first = true;
-	int idx, i;
-
-	assert_priolists(execlists, INT_MAX);
-
-	/* buckets sorted from highest [in slot 0] to lowest priority */
-	idx = I915_PRIORITY_COUNT - (prio & I915_PRIORITY_MASK) - 1;
-	prio >>= I915_USER_PRIORITY_SHIFT;
-	if (unlikely(execlists->no_priolist))
-		prio = I915_PRIORITY_NORMAL;
-
-find_priolist:
-	/* most positive priority is scheduled first, equal priorities fifo */
-	rb = NULL;
-	parent = &execlists->queue.rb_root.rb_node;
-	while (*parent) {
-		rb = *parent;
-		p = to_priolist(rb);
-		if (prio > p->priority) {
-			parent = &rb->rb_left;
-		} else if (prio < p->priority) {
-			parent = &rb->rb_right;
-			first = false;
-		} else {
-			goto out;
-		}
-	}
-
-	if (prio == I915_PRIORITY_NORMAL) {
-		p = &execlists->default_priolist;
-	} else {
-		p = kmem_cache_alloc(engine->i915->priorities, GFP_ATOMIC);
-		/* Convert an allocation failure to a priority bump */
-		if (unlikely(!p)) {
-			prio = I915_PRIORITY_NORMAL; /* recurses just once */
-
-			/* To maintain ordering with all rendering, after an
-			 * allocation failure we have to disable all scheduling.
-			 * Requests will then be executed in fifo, and schedule
-			 * will ensure that dependencies are emitted in fifo.
-			 * There will be still some reordering with existing
-			 * requests, so if userspace lied about their
-			 * dependencies that reordering may be visible.
-			 */
-			execlists->no_priolist = true;
-			goto find_priolist;
-		}
-	}
-
-	p->priority = prio;
-	for (i = 0; i < ARRAY_SIZE(p->requests); i++)
-		INIT_LIST_HEAD(&p->requests[i]);
-	rb_link_node(&p->node, rb, parent);
-	rb_insert_color_cached(&p->node, &execlists->queue, first);
-	p->used = 0;
-
-out:
-	p->used |= BIT(idx);
-	return &p->requests[idx];
-}
-
 static void unwind_wa_tail(struct i915_request *rq)
 {
 	rq->tail = intel_ring_wrap(rq->ring, rq->wa_tail - WA_TAIL_BYTES);
···
 		GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
 		if (rq_prio(rq) != prio) {
 			prio = rq_prio(rq);
-			pl = lookup_priolist(engine, prio);
+			pl = i915_sched_lookup_priolist(engine, prio);
 		}
 		GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
 
···
 	if (!(prio & I915_PRIORITY_NEWCLIENT)) {
 		prio |= I915_PRIORITY_NEWCLIENT;
 		list_move_tail(&active->sched.link,
-			       lookup_priolist(engine, prio));
+			       i915_sched_lookup_priolist(engine, prio));
 	}
 }
 
···
 	 */
 	execlists->queue_priority =
 		port != execlists->port ? rq_prio(last) : INT_MIN;
-	assert_priolists(execlists, execlists->queue_priority);
 
 	if (submit) {
 		port_assign(port, last);
···
 			  struct i915_sched_node *node,
 			  int prio)
 {
-	list_add_tail(&node->link, lookup_priolist(engine, prio));
-}
-
-static void __update_queue(struct intel_engine_cs *engine, int prio)
-{
-	engine->execlists.queue_priority = prio;
+	list_add_tail(&node->link, i915_sched_lookup_priolist(engine, prio));
 }
 
 static void __submit_queue_imm(struct intel_engine_cs *engine)
···
 static void submit_queue(struct intel_engine_cs *engine, int prio)
 {
 	if (prio > engine->execlists.queue_priority) {
-		__update_queue(engine, prio);
+		engine->execlists.queue_priority = prio;
 		__submit_queue_imm(engine);
 	}
 }
···
 	submit_queue(engine, rq_prio(request));
 
 	spin_unlock_irqrestore(&engine->timeline.lock, flags);
-}
-
-static struct i915_request *sched_to_request(struct i915_sched_node *node)
-{
-	return container_of(node, struct i915_request, sched);
-}
-
-static struct intel_engine_cs *
-sched_lock_engine(struct i915_sched_node *node, struct intel_engine_cs *locked)
-{
-	struct intel_engine_cs *engine = sched_to_request(node)->engine;
-
-	GEM_BUG_ON(!locked);
-
-	if (engine != locked) {
-		spin_unlock(&locked->timeline.lock);
-		spin_lock(&engine->timeline.lock);
-	}
-
-	return engine;
-}
-
-static void execlists_schedule(struct i915_request *request,
-			       const struct i915_sched_attr *attr)
-{
-	struct list_head *uninitialized_var(pl);
-	struct intel_engine_cs *engine, *last;
-	struct i915_dependency *dep, *p;
-	struct i915_dependency stack;
-	const int prio = attr->priority;
-	LIST_HEAD(dfs);
-
-	GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
-
-	if (i915_request_completed(request))
-		return;
-
-	if (prio <= READ_ONCE(request->sched.attr.priority))
-		return;
-
-	/* Need BKL in order to use the temporary link inside i915_dependency */
-	lockdep_assert_held(&request->i915->drm.struct_mutex);
-
-	stack.signaler = &request->sched;
-	list_add(&stack.dfs_link, &dfs);
-
-	/*
-	 * Recursively bump all dependent priorities to match the new request.
-	 *
-	 * A naive approach would be to use recursion:
-	 * static void update_priorities(struct i915_sched_node *node, prio) {
-	 *	list_for_each_entry(dep, &node->signalers_list, signal_link)
-	 *		update_priorities(dep->signal, prio)
-	 *	queue_request(node);
-	 * }
-	 * but that may have unlimited recursion depth and so runs a very
-	 * real risk of overunning the kernel stack. Instead, we build
-	 * a flat list of all dependencies starting with the current request.
-	 * As we walk the list of dependencies, we add all of its dependencies
-	 * to the end of the list (this may include an already visited
-	 * request) and continue to walk onwards onto the new dependencies. The
-	 * end result is a topological list of requests in reverse order, the
-	 * last element in the list is the request we must execute first.
-	 */
-	list_for_each_entry(dep, &dfs, dfs_link) {
-		struct i915_sched_node *node = dep->signaler;
-
-		/*
-		 * Within an engine, there can be no cycle, but we may
-		 * refer to the same dependency chain multiple times
-		 * (redundant dependencies are not eliminated) and across
-		 * engines.
-		 */
-		list_for_each_entry(p, &node->signalers_list, signal_link) {
-			GEM_BUG_ON(p == dep); /* no cycles! */
-
-			if (i915_sched_node_signaled(p->signaler))
-				continue;
-
-			GEM_BUG_ON(p->signaler->attr.priority < node->attr.priority);
-			if (prio > READ_ONCE(p->signaler->attr.priority))
-				list_move_tail(&p->dfs_link, &dfs);
-		}
-	}
-
-	/*
-	 * If we didn't need to bump any existing priorities, and we haven't
-	 * yet submitted this request (i.e. there is no potential race with
-	 * execlists_submit_request()), we can set our own priority and skip
-	 * acquiring the engine locks.
-	 */
-	if (request->sched.attr.priority == I915_PRIORITY_INVALID) {
-		GEM_BUG_ON(!list_empty(&request->sched.link));
-		request->sched.attr = *attr;
-		if (stack.dfs_link.next == stack.dfs_link.prev)
-			return;
-		__list_del_entry(&stack.dfs_link);
-	}
-
-	last = NULL;
-	engine = request->engine;
-	spin_lock_irq(&engine->timeline.lock);
-
-	/* Fifo and depth-first replacement ensure our deps execute before us */
-	list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {
-		struct i915_sched_node *node = dep->signaler;
-
-		INIT_LIST_HEAD(&dep->dfs_link);
-
-		engine = sched_lock_engine(node, engine);
-
-		/* Recheck after acquiring the engine->timeline.lock */
-		if (prio <= node->attr.priority)
-			continue;
-
-		if (i915_sched_node_signaled(node))
-			continue;
-
-		node->attr.priority = prio;
-		if (!list_empty(&node->link)) {
-			if (last != engine) {
-				pl = lookup_priolist(engine, prio);
-				last = engine;
-			}
-			list_move_tail(&node->link, pl);
-		} else {
-			/*
-			 * If the request is not in the priolist queue because
-			 * it is not yet runnable, then it doesn't contribute
-			 * to our preemption decisions. On the other hand,
-			 * if the request is on the HW, it too is not in the
-			 * queue; but in that case we may still need to reorder
-			 * the inflight requests.
-			 */
-			if (!i915_sw_fence_done(&sched_to_request(node)->submit))
-				continue;
-		}
-
-		if (prio <= engine->execlists.queue_priority)
-			continue;
-
-		/*
-		 * If we are already the currently executing context, don't
-		 * bother evaluating if we should preempt ourselves.
-		 */
-		if (sched_to_request(node)->global_seqno &&
-		    i915_seqno_passed(port_request(engine->execlists.port)->global_seqno,
-				      sched_to_request(node)->global_seqno))
-			continue;
-
-		/* Defer (tasklet) submission until after all of our updates. */
-		__update_queue(engine, prio);
-		tasklet_hi_schedule(&engine->execlists.tasklet);
-	}
-
-	spin_unlock_irq(&engine->timeline.lock);
 }
 
 static void execlists_context_destroy(struct intel_context *ce)
···
 {
 	engine->submit_request = execlists_submit_request;
 	engine->cancel_requests = execlists_cancel_requests;
-	engine->schedule = execlists_schedule;
+	engine->schedule = i915_schedule;
 	engine->execlists.tasklet.func = execlists_submission_tasklet;
 
 	engine->reset.prepare = execlists_reset_prepare;

drivers/gpu/drm/i915/intel_ringbuffer.h

···
 	 */
 	void		(*submit_request)(struct i915_request *rq);
 
-	/* Call when the priority on a request has changed and it and its
+	/*
+	 * Call when the priority on a request has changed and it and its
 	 * dependencies may need rescheduling. Note the request itself may
 	 * not be ready to run!
-	 *
-	 * Called under the struct_mutex.
 	 */
 	void		(*schedule)(struct i915_request *request,
 				    const struct i915_sched_attr *attr);