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 <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181001144755.7978-2-chris@chris-wilson.co.uk

1 files changed, 5 insertions, 263 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 5f324d6b44d5..28d56387edf5 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -259,102 +259,6 @@ intel_lr_context_descriptor_update(struct i915_gem_context *ctx,
 	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);
@@ -381,7 +285,7 @@ static void __unwind_incomplete_requests(struct intel_engine_cs *engine)
 		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));
 
@@ -398,7 +302,7 @@ static void __unwind_incomplete_requests(struct intel_engine_cs *engine)
 	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));
 	}
 }
 
@@ -792,7 +696,6 @@ done:
 	 */
 	execlists->queue_priority =
 		port != execlists->port ? rq_prio(last) : INT_MIN;
-	assert_priolists(execlists, execlists->queue_priority);
 
 	if (submit) {
 		port_assign(port, last);
@@ -1119,12 +1022,7 @@ static void queue_request(struct intel_engine_cs *engine,
 			  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)
@@ -1143,7 +1041,7 @@ 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);
 	}
 }
@@ -1166,162 +1064,6 @@ static void execlists_submit_request(struct i915_request *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)
 {
 	GEM_BUG_ON(ce->pin_count);
@@ -2359,7 +2101,7 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 {
 	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;