drm/i915: Protect request retirement with timeline->mutex

Forgo the struct_mutex requirement for request retirement as we have
been transitioning over to only using the timeline->mutex for
controlling the lifetime of a request on that timeline.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190815205709.24285-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -735,63 +735,6 @@ static int eb_select_context(struct i915_execbuffer *eb)
 	return 0;
 }
 
-static struct i915_request *__eb_wait_for_ring(struct intel_ring *ring)
-{
-	struct i915_request *rq;
-
-	/*
-	 * Completely unscientific finger-in-the-air estimates for suitable
-	 * maximum user request size (to avoid blocking) and then backoff.
-	 */
-	if (intel_ring_update_space(ring) >= PAGE_SIZE)
-		return NULL;
-
-	/*
-	 * Find a request that after waiting upon, there will be at least half
-	 * the ring available. The hysteresis allows us to compete for the
-	 * shared ring and should mean that we sleep less often prior to
-	 * claiming our resources, but not so long that the ring completely
-	 * drains before we can submit our next request.
-	 */
-	list_for_each_entry(rq, &ring->request_list, ring_link) {
-		if (__intel_ring_space(rq->postfix,
-				       ring->emit, ring->size) > ring->size / 2)
-			break;
-	}
-	if (&rq->ring_link == &ring->request_list)
-		return NULL; /* weird, we will check again later for real */
-
-	return i915_request_get(rq);
-}
-
-static int eb_wait_for_ring(const struct i915_execbuffer *eb)
-{
-	struct i915_request *rq;
-	int ret = 0;
-
-	/*
-	 * Apply a light amount of backpressure to prevent excessive hogs
-	 * from blocking waiting for space whilst holding struct_mutex and
-	 * keeping all of their resources pinned.
-	 */
-
-	rq = __eb_wait_for_ring(eb->context->ring);
-	if (rq) {
-		mutex_unlock(&eb->i915->drm.struct_mutex);
-
-		if (i915_request_wait(rq,
-				      I915_WAIT_INTERRUPTIBLE,
-				      MAX_SCHEDULE_TIMEOUT) < 0)
-			ret = -EINTR;
-
-		i915_request_put(rq);
-
-		mutex_lock(&eb->i915->drm.struct_mutex);
-	}
-
-	return ret;
-}
-
 static int eb_lookup_vmas(struct i915_execbuffer *eb)
 {
 	struct radix_tree_root *handles_vma = &eb->gem_context->handles_vma;
@@ -2134,10 +2077,75 @@ static const enum intel_engine_id user_ring_map[] = {
 	[I915_EXEC_VEBOX]	= VECS0
 };
 
-static int eb_pin_context(struct i915_execbuffer *eb, struct intel_context *ce)
+static struct i915_request *eb_throttle(struct intel_context *ce)
+{
+	struct intel_ring *ring = ce->ring;
+	struct intel_timeline *tl = ce->timeline;
+	struct i915_request *rq;
+
+	/*
+	 * Completely unscientific finger-in-the-air estimates for suitable
+	 * maximum user request size (to avoid blocking) and then backoff.
+	 */
+	if (intel_ring_update_space(ring) >= PAGE_SIZE)
+		return NULL;
+
+	/*
+	 * Find a request that after waiting upon, there will be at least half
+	 * the ring available. The hysteresis allows us to compete for the
+	 * shared ring and should mean that we sleep less often prior to
+	 * claiming our resources, but not so long that the ring completely
+	 * drains before we can submit our next request.
+	 */
+	list_for_each_entry(rq, &tl->requests, link) {
+		if (rq->ring != ring)
+			continue;
+
+		if (__intel_ring_space(rq->postfix,
+				       ring->emit, ring->size) > ring->size / 2)
+			break;
+	}
+	if (&rq->link == &tl->requests)
+		return NULL; /* weird, we will check again later for real */
+
+	return i915_request_get(rq);
+}
+
+static int
+__eb_pin_context(struct i915_execbuffer *eb, struct intel_context *ce)
 {
 	int err;
 
+	if (likely(atomic_inc_not_zero(&ce->pin_count)))
+		return 0;
+
+	err = mutex_lock_interruptible(&eb->i915->drm.struct_mutex);
+	if (err)
+		return err;
+
+	err = __intel_context_do_pin(ce);
+	mutex_unlock(&eb->i915->drm.struct_mutex);
+
+	return err;
+}
+
+static void
+__eb_unpin_context(struct i915_execbuffer *eb, struct intel_context *ce)
+{
+	if (likely(atomic_add_unless(&ce->pin_count, -1, 1)))
+		return;
+
+	mutex_lock(&eb->i915->drm.struct_mutex);
+	intel_context_unpin(ce);
+	mutex_unlock(&eb->i915->drm.struct_mutex);
+}
+
+static int __eb_pin_engine(struct i915_execbuffer *eb, struct intel_context *ce)
+{
+	struct intel_timeline *tl;
+	struct i915_request *rq;
+	int err;
+
 	/*
 	 * ABI: Before userspace accesses the GPU (e.g. execbuffer), report
 	 * EIO if the GPU is already wedged.
@@ -2151,7 +2159,7 @@ static int eb_pin_context(struct i915_execbuffer *eb, struct intel_context *ce)
 	 * GGTT space, so do this first before we reserve a seqno for
 	 * ourselves.
 	 */
-	err = intel_context_pin(ce);
+	err = __eb_pin_context(eb, ce);
 	if (err)
 		return err;
 
@@ -2163,23 +2171,43 @@ static int eb_pin_context(struct i915_execbuffer *eb, struct intel_context *ce)
 	 * until the timeline is idle, which in turn releases the wakeref
 	 * taken on the engine, and the parent device.
 	 */
-	err = intel_context_timeline_lock(ce);
-	if (err)
+	tl = intel_context_timeline_lock(ce);
+	if (IS_ERR(tl)) {
+		err = PTR_ERR(tl);
 		goto err_unpin;
+	}
 
 	intel_context_enter(ce);
-	intel_context_timeline_unlock(ce);
+	rq = eb_throttle(ce);
+
+	intel_context_timeline_unlock(tl);
+
+	if (rq) {
+		if (i915_request_wait(rq,
+				      I915_WAIT_INTERRUPTIBLE,
+				      MAX_SCHEDULE_TIMEOUT) < 0) {
+			i915_request_put(rq);
+			err = -EINTR;
+			goto err_exit;
+		}
+
+		i915_request_put(rq);
+	}
 
 	eb->engine = ce->engine;
 	eb->context = ce;
 	return 0;
 
+err_exit:
+	mutex_lock(&tl->mutex);
+	intel_context_exit(ce);
+	intel_context_timeline_unlock(tl);
 err_unpin:
-	intel_context_unpin(ce);
+	__eb_unpin_context(eb, ce);
 	return err;
 }
 
-static void eb_unpin_context(struct i915_execbuffer *eb)
+static void eb_unpin_engine(struct i915_execbuffer *eb)
 {
 	struct intel_context *ce = eb->context;
 	struct intel_timeline *tl = ce->timeline;
@@ -2188,7 +2216,7 @@ static void eb_unpin_context(struct i915_execbuffer *eb)
 	intel_context_exit(ce);
 	mutex_unlock(&tl->mutex);
 
-	intel_context_unpin(ce);
+	__eb_unpin_context(eb, ce);
 }
 
 static unsigned int
@@ -2233,9 +2261,9 @@ eb_select_legacy_ring(struct i915_execbuffer *eb,
 }
 
 static int
-eb_select_engine(struct i915_execbuffer *eb,
-		 struct drm_file *file,
-		 struct drm_i915_gem_execbuffer2 *args)
+eb_pin_engine(struct i915_execbuffer *eb,
+	      struct drm_file *file,
+	      struct drm_i915_gem_execbuffer2 *args)
 {
 	struct intel_context *ce;
 	unsigned int idx;
@@ -2250,7 +2278,7 @@ eb_select_engine(struct i915_execbuffer *eb,
 	if (IS_ERR(ce))
 		return PTR_ERR(ce);
 
-	err = eb_pin_context(eb, ce);
+	err = __eb_pin_engine(eb, ce);
 	intel_context_put(ce);
 
 	return err;
@@ -2468,16 +2496,12 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	if (unlikely(err))
 		goto err_destroy;
 
-	err = i915_mutex_lock_interruptible(dev);
-	if (err)
-		goto err_context;
-
-	err = eb_select_engine(&eb, file, args);
+	err = eb_pin_engine(&eb, file, args);
 	if (unlikely(err))
-		goto err_unlock;
+		goto err_context;
 
-	err = eb_wait_for_ring(&eb); /* may temporarily drop struct_mutex */
-	if (unlikely(err))
+	err = i915_mutex_lock_interruptible(dev);
+	if (err)
 		goto err_engine;
 
 	err = eb_relocate(&eb);
@@ -2635,10 +2659,9 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 err_vma:
 	if (eb.exec)
 		eb_release_vmas(&eb);
-err_engine:
-	eb_unpin_context(&eb);
-err_unlock:
 	mutex_unlock(&dev->struct_mutex);
+err_engine:
+	eb_unpin_engine(&eb);
 err_context:
 	i915_gem_context_put(eb.gem_context);
 err_destroy:

drivers/gpu/drm/i915/gt/intel_context.h

@@ -12,6 +12,7 @@
 #include "i915_active.h"
 #include "intel_context_types.h"
 #include "intel_engine_types.h"
+#include "intel_timeline_types.h"
 
 void intel_context_init(struct intel_context *ce,
 			struct i915_gem_context *ctx,
@@ -118,17 +119,24 @@ static inline void intel_context_put(struct intel_context *ce)
 	kref_put(&ce->ref, ce->ops->destroy);
 }
 
-static inline int __must_check
+static inline struct intel_timeline *__must_check
 intel_context_timeline_lock(struct intel_context *ce)
 	__acquires(&ce->timeline->mutex)
 {
-	return mutex_lock_interruptible(&ce->timeline->mutex);
+	struct intel_timeline *tl = ce->timeline;
+	int err;
+
+	err = mutex_lock_interruptible(&tl->mutex);
+	if (err)
+		return ERR_PTR(err);
+
+	return tl;
 }
 
-static inline void intel_context_timeline_unlock(struct intel_context *ce)
-	__releases(&ce->timeline->mutex)
+static inline void intel_context_timeline_unlock(struct intel_timeline *tl)
+	__releases(&tl->mutex)
 {
-	mutex_unlock(&ce->timeline->mutex);
+	mutex_unlock(&tl->mutex);
 }
 
 int intel_context_prepare_remote_request(struct intel_context *ce,

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -679,7 +679,6 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 				engine->status_page.vma))
 		goto out_frame;
 
-	INIT_LIST_HEAD(&frame->ring.request_list);
 	frame->ring.vaddr = frame->cs;
 	frame->ring.size = sizeof(frame->cs);
 	frame->ring.effective_size = frame->ring.size;

drivers/gpu/drm/i915/gt/intel_engine_types.h

@@ -69,9 +69,6 @@ struct intel_ring {
 	struct i915_vma *vma;
 	void *vaddr;
 
-	struct list_head request_list;
-	struct list_head active_link;
-
 	/*
 	 * As we have two types of rings, one global to the engine used
 	 * by ringbuffer submission and those that are exclusive to a

drivers/gpu/drm/i915/gt/intel_gt.c

@@ -15,8 +15,6 @@ void intel_gt_init_early(struct intel_gt *gt, struct drm_i915_private *i915)
 
 	spin_lock_init(&gt->irq_lock);
 
-	INIT_LIST_HEAD(&gt->active_rings);
-
 	INIT_LIST_HEAD(&gt->closed_vma);
 	spin_lock_init(&gt->closed_lock);
 

drivers/gpu/drm/i915/gt/intel_gt_types.h

@@ -48,8 +48,6 @@ struct intel_gt {
 		struct list_head hwsp_free_list;
 	} timelines;
 
-	struct list_head active_rings;
-
 	struct intel_wakeref wakeref;
 
 	struct list_head closed_vma;

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -1583,6 +1583,7 @@ static void execlists_context_unpin(struct intel_context *ce)
 {
 	i915_gem_context_unpin_hw_id(ce->gem_context);
 	i915_gem_object_unpin_map(ce->state->obj);
+	intel_ring_reset(ce->ring, ce->ring->tail);
 }
 
 static void

drivers/gpu/drm/i915/gt/intel_ringbuffer.c

@@ -1250,7 +1250,7 @@ void intel_ring_unpin(struct intel_ring *ring)
 		return;
 
 	/* Discard any unused bytes beyond that submitted to hw. */
-	intel_ring_reset(ring, ring->tail);
+	intel_ring_reset(ring, ring->emit);
 
 	i915_vma_unset_ggtt_write(vma);
 	if (i915_vma_is_map_and_fenceable(vma))
@@ -1311,7 +1311,6 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size)
 		return ERR_PTR(-ENOMEM);
 
 	kref_init(&ring->ref);
-	INIT_LIST_HEAD(&ring->request_list);
 
 	ring->size = size;
 	/* Workaround an erratum on the i830 which causes a hang if
@@ -1865,7 +1864,10 @@ static int ring_request_alloc(struct i915_request *request)
 	return 0;
 }
 
-static noinline int wait_for_space(struct intel_ring *ring, unsigned int bytes)
+static noinline int
+wait_for_space(struct intel_ring *ring,
+	       struct intel_timeline *tl,
+	       unsigned int bytes)
 {
 	struct i915_request *target;
 	long timeout;
@@ -1873,15 +1875,18 @@ static noinline int wait_for_space(struct intel_ring *ring, unsigned int bytes)
 	if (intel_ring_update_space(ring) >= bytes)
 		return 0;
 
-	GEM_BUG_ON(list_empty(&ring->request_list));
-	list_for_each_entry(target, &ring->request_list, ring_link) {
+	GEM_BUG_ON(list_empty(&tl->requests));
+	list_for_each_entry(target, &tl->requests, link) {
+		if (target->ring != ring)
+			continue;
+
 		/* Would completion of this request free enough space? */
 		if (bytes <= __intel_ring_space(target->postfix,
 						ring->emit, ring->size))
 			break;
 	}
 
-	if (WARN_ON(&target->ring_link == &ring->request_list))
+	if (GEM_WARN_ON(&target->link == &tl->requests))
 		return -ENOSPC;
 
 	timeout = i915_request_wait(target,
@@ -1948,7 +1953,7 @@ u32 *intel_ring_begin(struct i915_request *rq, unsigned int num_dwords)
 		 */
 		GEM_BUG_ON(!rq->reserved_space);
 
-		ret = wait_for_space(ring, total_bytes);
+		ret = wait_for_space(ring, rq->timeline, total_bytes);
 		if (unlikely(ret))
 			return ERR_PTR(ret);
 	}

drivers/gpu/drm/i915/gt/mock_engine.c

@@ -58,7 +58,6 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 	ring->vaddr = (void *)(ring + 1);
 	atomic_set(&ring->pin_count, 1);
 
-	INIT_LIST_HEAD(&ring->request_list);
 	intel_ring_update_space(ring);
 
 	return ring;

drivers/gpu/drm/i915/gt/selftest_context.c

@@ -20,10 +20,13 @@ static int request_sync(struct i915_request *rq)
 
 	i915_request_add(rq);
 	timeout = i915_request_wait(rq, 0, HZ / 10);
-	if (timeout < 0)
+	if (timeout < 0) {
 		err = timeout;
-	else
+	} else {
+		mutex_lock(&rq->timeline->mutex);
 		i915_request_retire_upto(rq);
+		mutex_unlock(&rq->timeline->mutex);
+	}
 
 	i915_request_put(rq);
 
@@ -35,6 +38,7 @@ static int context_sync(struct intel_context *ce)
 	struct intel_timeline *tl = ce->timeline;
 	int err = 0;
 
+	mutex_lock(&tl->mutex);
 	do {
 		struct i915_request *rq;
 		long timeout;
@@ -55,6 +59,7 @@ static int context_sync(struct intel_context *ce)
 
 		i915_request_put(rq);
 	} while (!err);
+	mutex_unlock(&tl->mutex);
 
 	return err;
 }

drivers/gpu/drm/i915/i915_request.c

@@ -181,40 +181,6 @@ i915_request_remove_from_client(struct i915_request *request)
 	spin_unlock(&file_priv->mm.lock);
 }
 
-static void advance_ring(struct i915_request *request)
-{
-	struct intel_ring *ring = request->ring;
-	unsigned int tail;
-
-	/*
-	 * We know the GPU must have read the request to have
-	 * sent us the seqno + interrupt, so use the position
-	 * of tail of the request to update the last known position
-	 * of the GPU head.
-	 *
-	 * Note this requires that we are always called in request
-	 * completion order.
-	 */
-	GEM_BUG_ON(!list_is_first(&request->ring_link, &ring->request_list));
-	if (list_is_last(&request->ring_link, &ring->request_list)) {
-		/*
-		 * We may race here with execlists resubmitting this request
-		 * as we retire it. The resubmission will move the ring->tail
-		 * forwards (to request->wa_tail). We either read the
-		 * current value that was written to hw, or the value that
-		 * is just about to be. Either works, if we miss the last two
-		 * noops - they are safe to be replayed on a reset.
-		 */
-		tail = READ_ONCE(request->tail);
-		list_del(&ring->active_link);
-	} else {
-		tail = request->postfix;
-	}
-	list_del_init(&request->ring_link);
-
-	ring->head = tail;
-}
-
 static void free_capture_list(struct i915_request *request)
 {
 	struct i915_capture_list *capture;
@@ -232,7 +198,7 @@ static bool i915_request_retire(struct i915_request *rq)
 {
 	struct i915_active_request *active, *next;
 
-	lockdep_assert_held(&rq->i915->drm.struct_mutex);
+	lockdep_assert_held(&rq->timeline->mutex);
 	if (!i915_request_completed(rq))
 		return false;
 
@@ -244,7 +210,17 @@ static bool i915_request_retire(struct i915_request *rq)
 	GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit));
 	trace_i915_request_retire(rq);
 
-	advance_ring(rq);
+	/*
+	 * We know the GPU must have read the request to have
+	 * sent us the seqno + interrupt, so use the position
+	 * of tail of the request to update the last known position
+	 * of the GPU head.
+	 *
+	 * Note this requires that we are always called in request
+	 * completion order.
+	 */
+	GEM_BUG_ON(!list_is_first(&rq->link, &rq->timeline->requests));
+	rq->ring->head = rq->postfix;
 
 	/*
 	 * Walk through the active list, calling retire on each. This allows
@@ -321,7 +297,7 @@ static bool i915_request_retire(struct i915_request *rq)
 
 void i915_request_retire_upto(struct i915_request *rq)
 {
-	struct intel_ring *ring = rq->ring;
+	struct intel_timeline * const tl = rq->timeline;
 	struct i915_request *tmp;
 
 	GEM_TRACE("%s fence %llx:%lld, current %d\n",
@@ -329,15 +305,11 @@ void i915_request_retire_upto(struct i915_request *rq)
 		  rq->fence.context, rq->fence.seqno,
 		  hwsp_seqno(rq));
 
-	lockdep_assert_held(&rq->i915->drm.struct_mutex);
+	lockdep_assert_held(&tl->mutex);
 	GEM_BUG_ON(!i915_request_completed(rq));
 
-	if (list_empty(&rq->ring_link))
-		return;
-
 	do {
-		tmp = list_first_entry(&ring->request_list,
-				       typeof(*tmp), ring_link);
+		tmp = list_first_entry(&tl->requests, typeof(*tmp), link);
 	} while (i915_request_retire(tmp) && tmp != rq);
 }
 
@@ -564,29 +536,28 @@ semaphore_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
 	return NOTIFY_DONE;
 }
 
-static void ring_retire_requests(struct intel_ring *ring)
+static void retire_requests(struct intel_timeline *tl)
 {
 	struct i915_request *rq, *rn;
 
-	list_for_each_entry_safe(rq, rn, &ring->request_list, ring_link)
+	list_for_each_entry_safe(rq, rn, &tl->requests, link)
 		if (!i915_request_retire(rq))
 			break;
 }
 
 static noinline struct i915_request *
-request_alloc_slow(struct intel_context *ce, gfp_t gfp)
+request_alloc_slow(struct intel_timeline *tl, gfp_t gfp)
 {
-	struct intel_ring *ring = ce->ring;
 	struct i915_request *rq;
 
-	if (list_empty(&ring->request_list))
+	if (list_empty(&tl->requests))
 		goto out;
 
 	if (!gfpflags_allow_blocking(gfp))
 		goto out;
 
 	/* Move our oldest request to the slab-cache (if not in use!) */
-	rq = list_first_entry(&ring->request_list, typeof(*rq), ring_link);
+	rq = list_first_entry(&tl->requests, typeof(*rq), link);
 	i915_request_retire(rq);
 
 	rq = kmem_cache_alloc(global.slab_requests,
@@ -595,11 +566,11 @@ request_alloc_slow(struct intel_context *ce, gfp_t gfp)
 		return rq;
 
 	/* Ratelimit ourselves to prevent oom from malicious clients */
-	rq = list_last_entry(&ring->request_list, typeof(*rq), ring_link);
+	rq = list_last_entry(&tl->requests, typeof(*rq), link);
 	cond_synchronize_rcu(rq->rcustate);
 
 	/* Retire our old requests in the hope that we free some */
-	ring_retire_requests(ring);
+	retire_requests(tl);
 
 out:
 	return kmem_cache_alloc(global.slab_requests, gfp);
@@ -650,7 +621,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
 	rq = kmem_cache_alloc(global.slab_requests,
 			      gfp | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
 	if (unlikely(!rq)) {
-		rq = request_alloc_slow(ce, gfp);
+		rq = request_alloc_slow(tl, gfp);
 		if (!rq) {
 			ret = -ENOMEM;
 			goto err_unreserve;
@@ -742,15 +713,15 @@ struct i915_request *
 i915_request_create(struct intel_context *ce)
 {
 	struct i915_request *rq;
-	int err;
+	struct intel_timeline *tl;
 
-	err = intel_context_timeline_lock(ce);
-	if (err)
-		return ERR_PTR(err);
+	tl = intel_context_timeline_lock(ce);
+	if (IS_ERR(tl))
+		return ERR_CAST(tl);
 
 	/* Move our oldest request to the slab-cache (if not in use!) */
-	rq = list_first_entry(&ce->ring->request_list, typeof(*rq), ring_link);
-	if (!list_is_last(&rq->ring_link, &ce->ring->request_list))
+	rq = list_first_entry(&tl->requests, typeof(*rq), link);
+	if (!list_is_last(&rq->link, &tl->requests))
 		i915_request_retire(rq);
 
 	intel_context_enter(ce);
@@ -760,22 +731,22 @@ i915_request_create(struct intel_context *ce)
 		goto err_unlock;
 
 	/* Check that we do not interrupt ourselves with a new request */
-	rq->cookie = lockdep_pin_lock(&ce->timeline->mutex);
+	rq->cookie = lockdep_pin_lock(&tl->mutex);
 
 	return rq;
 
 err_unlock:
-	intel_context_timeline_unlock(ce);
+	intel_context_timeline_unlock(tl);
 	return rq;
 }
 
 static int
 i915_request_await_start(struct i915_request *rq, struct i915_request *signal)
 {
-	if (list_is_first(&signal->ring_link, &signal->ring->request_list))
+	if (list_is_first(&signal->link, &signal->timeline->requests))
 		return 0;
 
-	signal = list_prev_entry(signal, ring_link);
+	signal = list_prev_entry(signal, link);
 	if (intel_timeline_sync_is_later(rq->timeline, &signal->fence))
 		return 0;
 
@@ -1155,7 +1126,6 @@ struct i915_request *__i915_request_commit(struct i915_request *rq)
 {
 	struct intel_engine_cs *engine = rq->engine;
 	struct intel_ring *ring = rq->ring;
-	struct i915_request *prev;
 	u32 *cs;
 
 	GEM_TRACE("%s fence %llx:%lld\n",
@@ -1168,6 +1138,7 @@ struct i915_request *__i915_request_commit(struct i915_request *rq)
 	 */
 	GEM_BUG_ON(rq->reserved_space > ring->space);
 	rq->reserved_space = 0;
+	rq->emitted_jiffies = jiffies;
 
 	/*
 	 * Record the position of the start of the breadcrumb so that
@@ -1179,14 +1150,7 @@ struct i915_request *__i915_request_commit(struct i915_request *rq)
 	GEM_BUG_ON(IS_ERR(cs));
 	rq->postfix = intel_ring_offset(rq, cs);
 
-	prev = __i915_request_add_to_timeline(rq);
-
-	list_add_tail(&rq->ring_link, &ring->request_list);
-	if (list_is_first(&rq->ring_link, &ring->request_list))
-		list_add(&ring->active_link, &rq->i915->gt.active_rings);
-	rq->emitted_jiffies = jiffies;
-
-	return prev;
+	return __i915_request_add_to_timeline(rq);
 }
 
 void __i915_request_queue(struct i915_request *rq,
@@ -1212,10 +1176,11 @@ void __i915_request_queue(struct i915_request *rq,
 void i915_request_add(struct i915_request *rq)
 {
 	struct i915_sched_attr attr = rq->gem_context->sched;
+	struct intel_timeline * const tl = rq->timeline;
 	struct i915_request *prev;
 
-	lockdep_assert_held(&rq->timeline->mutex);
-	lockdep_unpin_lock(&rq->timeline->mutex, rq->cookie);
+	lockdep_assert_held(&tl->mutex);
+	lockdep_unpin_lock(&tl->mutex, rq->cookie);
 
 	trace_i915_request_add(rq);
 
@@ -1266,10 +1231,10 @@ void i915_request_add(struct i915_request *rq)
 	 * work on behalf of others -- but instead we should benefit from
 	 * improved resource management. (Well, that's the theory at least.)
 	 */
-	if (prev && i915_request_completed(prev))
+	if (prev && i915_request_completed(prev) && prev->timeline == tl)
 		i915_request_retire_upto(prev);
 
-	mutex_unlock(&rq->timeline->mutex);
+	mutex_unlock(&tl->mutex);
 }
 
 static unsigned long local_clock_us(unsigned int *cpu)
@@ -1489,18 +1454,43 @@ long i915_request_wait(struct i915_request *rq,
 
 bool i915_retire_requests(struct drm_i915_private *i915)
 {
-	struct intel_ring *ring, *tmp;
+	struct intel_gt_timelines *timelines = &i915->gt.timelines;
+	struct intel_timeline *tl, *tn;
+	LIST_HEAD(free);
+
+	spin_lock(&timelines->lock);
+	list_for_each_entry_safe(tl, tn, &timelines->active_list, link) {
+		if (!mutex_trylock(&tl->mutex))
+			continue;
 
-	lockdep_assert_held(&i915->drm.struct_mutex);
+		intel_timeline_get(tl);
+		GEM_BUG_ON(!tl->active_count);
+		tl->active_count++; /* pin the list element */
+		spin_unlock(&timelines->lock);
 
-	list_for_each_entry_safe(ring, tmp,
-				 &i915->gt.active_rings, active_link) {
-		intel_ring_get(ring); /* last rq holds reference! */
-		ring_retire_requests(ring);
-		intel_ring_put(ring);
+		retire_requests(tl);
+
+		spin_lock(&timelines->lock);
+
+		/* Resume iteration after dropping lock */
+		list_safe_reset_next(tl, tn, link);
+		if (!--tl->active_count)
+			list_del(&tl->link);
+
+		mutex_unlock(&tl->mutex);
+
+		/* Defer the final release to after the spinlock */
+		if (refcount_dec_and_test(&tl->kref.refcount)) {
+			GEM_BUG_ON(tl->active_count);
+			list_add(&tl->link, &free);
+		}
 	}
+	spin_unlock(&timelines->lock);
+
+	list_for_each_entry_safe(tl, tn, &free, link)
+		__intel_timeline_free(&tl->kref);
 
-	return !list_empty(&i915->gt.active_rings);
+	return !list_empty(&timelines->active_list);
 }
 
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)

drivers/gpu/drm/i915/i915_request.h

@@ -223,9 +223,6 @@ struct i915_request {
 	/** timeline->request entry for this request */
 	struct list_head link;
 
-	/** ring->request_list entry for this request */
-	struct list_head ring_link;
-
 	struct drm_i915_file_private *file_priv;
 	/** file_priv list entry for this request */
 	struct list_head client_link;