[49/50] drm/i915: Replace global breadcrumbs with per-context interrupt tracking

Submitted by Chris Wilson on Jan. 11, 2019, 11:53 p.m.

Details

Message ID 20190111235332.2032-49-chris@chris-wilson.co.uk
State New
Headers show
Series "Series without cover letter" ( rev: 1 ) in Intel GFX - Try Bot

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Commit Message

Chris Wilson Jan. 11, 2019, 11:53 p.m.
A few years ago, see commit 688e6c725816 ("drm/i915: Slaughter the
thundering i915_wait_request herd"), the issue of handling multiple
clients waiting in parallel was brought to our attention. The
requirement was that every client should be woken immediately upon its
request being signaled, without incurring any cpu overhead.

To handle certain fragility of our hw meant that we could not do a
simple check inside the irq handler (some generations required almost
unbounded delays before we could be sure of seqno coherency) and so
request completion checking required delegation.

Before commit 688e6c725816, the solution was simple. Every client waking
on a request would be woken on every interrupt and each would do a
heavyweight check to see if their request was complete. Commit
688e6c725816 introduced an rbtree so that only the earliest waiter on
the global timeline would woken, and would wake the next and so on.
(Along with various complications to handle requests being reordered
along the global timeline, and also a requirement for kthread to provide
a delegate for fence signaling that had no process context.)

The global rbtree depends on knowing the execution timeline (and global
seqno). Without knowing that order, we must instead check all contexts
queued to the HW to see which may have advanced. We trim that list by
only checking queued contexts that are being waited on, but still we
keep a list of all active contexts and their active signalers that we
inspect from inside the irq handler. By moving the waiters onto the fence
signal list, we can combine the client wakeup with the dma_fence
signaling (a dramatic reduction in complexity, but does require the HW
being coherent, the seqno must be visible from the cpu before the
interrupt is raised - we keep a timer backup just in case).

Having previously fixed all the issues with irq-seqno serialisation (by
inserting delays onto the GPU after each request instead of random delays
on the CPU after each interrupt), we can rely on the seqno state to
perfom direct wakeups from the interrupt handler. This allows us to
preserve our single context switch behaviour of the current routine,
with the only downside that we lose the RT priority sorting of wakeups.
In general, direct wakeup latency of multiple clients is about the same
(about 10% better in most cases) with a reduction in total CPU time spent
in the waiter (about 20-50% depending on gen). Average herd behaviour is
improved, but at the cost of not delegating wakeups on task_prio.

References: 688e6c725816 ("drm/i915: Slaughter the thundering i915_wait_request herd")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_debugfs.c           |  28 +-
 drivers/gpu/drm/i915/i915_gem_context.c       |   2 +
 drivers/gpu/drm/i915/i915_gem_context.h       |   2 +
 drivers/gpu/drm/i915/i915_gpu_error.c         |  73 --
 drivers/gpu/drm/i915/i915_gpu_error.h         |   8 -
 drivers/gpu/drm/i915/i915_irq.c               |  88 +-
 drivers/gpu/drm/i915/i915_request.c           | 128 +--
 drivers/gpu/drm/i915/i915_request.h           |  22 +-
 drivers/gpu/drm/i915/i915_reset.c             |  13 +-
 drivers/gpu/drm/i915/intel_breadcrumbs.c      | 806 +++++-------------
 drivers/gpu/drm/i915/intel_engine_cs.c        |  34 +-
 drivers/gpu/drm/i915/intel_ringbuffer.c       |   6 +-
 drivers/gpu/drm/i915/intel_ringbuffer.h       |  95 +--
 .../drm/i915/selftests/i915_mock_selftests.h  |   1 -
 drivers/gpu/drm/i915/selftests/i915_request.c | 398 +++++++++
 drivers/gpu/drm/i915/selftests/igt_spinner.c  |   5 -
 .../drm/i915/selftests/intel_breadcrumbs.c    | 470 ----------
 .../gpu/drm/i915/selftests/intel_hangcheck.c  |   2 +-
 drivers/gpu/drm/i915/selftests/lib_sw_fence.c |  54 ++
 drivers/gpu/drm/i915/selftests/lib_sw_fence.h |   3 +
 drivers/gpu/drm/i915/selftests/mock_context.c |   2 +
 drivers/gpu/drm/i915/selftests/mock_engine.c  |  26 +-
 drivers/gpu/drm/i915/selftests/mock_engine.h  |   6 -
 23 files changed, 779 insertions(+), 1493 deletions(-)
 delete mode 100644 drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index a1ffe53b9fbe..f12e5a4863d6 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1315,29 +1315,16 @@  static int i915_hangcheck_info(struct seq_file *m, void *unused)
 	seq_printf(m, "GT active? %s\n", yesno(dev_priv->gt.awake));
 
 	for_each_engine(engine, dev_priv, id) {
-		struct intel_breadcrumbs *b = &engine->breadcrumbs;
-		struct rb_node *rb;
-
 		seq_printf(m, "%s:\n", engine->name);
 		seq_printf(m, "\tseqno = %x [current %x, last %x]\n",
 			   engine->hangcheck.seqno, seqno[id],
 			   intel_engine_last_submit(engine));
-		seq_printf(m, "\twaiters? %s, fake irq active? %s, stalled? %s, wedged? %s\n",
-			   yesno(intel_engine_has_waiter(engine)),
+		seq_printf(m, "\tfake irq active? %s, stalled? %s, wedged? %s\n",
 			   yesno(test_bit(engine->id,
 					  &dev_priv->gpu_error.missed_irq_rings)),
 			   yesno(engine->hangcheck.stalled),
 			   yesno(engine->hangcheck.wedged));
 
-		spin_lock_irq(&b->rb_lock);
-		for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
-			struct intel_wait *w = rb_entry(rb, typeof(*w), node);
-
-			seq_printf(m, "\t%s [%d] waiting for %x\n",
-				   w->tsk->comm, w->tsk->pid, w->seqno);
-		}
-		spin_unlock_irq(&b->rb_lock);
-
 		seq_printf(m, "\tACTHD = 0x%08llx [current 0x%08llx]\n",
 			   (long long)engine->hangcheck.acthd,
 			   (long long)acthd[id]);
@@ -2026,18 +2013,6 @@  static int i915_swizzle_info(struct seq_file *m, void *data)
 	return 0;
 }
 
-static int count_irq_waiters(struct drm_i915_private *i915)
-{
-	struct intel_engine_cs *engine;
-	enum intel_engine_id id;
-	int count = 0;
-
-	for_each_engine(engine, i915, id)
-		count += intel_engine_has_waiter(engine);
-
-	return count;
-}
-
 static const char *rps_power_to_str(unsigned int power)
 {
 	static const char * const strings[] = {
@@ -2077,7 +2052,6 @@  static int i915_rps_boost_info(struct seq_file *m, void *data)
 	seq_printf(m, "RPS enabled? %d\n", rps->enabled);
 	seq_printf(m, "GPU busy? %s [%d requests]\n",
 		   yesno(dev_priv->gt.awake), dev_priv->gt.active_requests);
-	seq_printf(m, "CPU waiting? %d\n", count_irq_waiters(dev_priv));
 	seq_printf(m, "Boosts outstanding? %d\n",
 		   atomic_read(&rps->num_waiters));
 	seq_printf(m, "Interactive? %d\n", READ_ONCE(rps->power.interactive));
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 5933adbe3d99..054d3e1bfe00 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -342,6 +342,8 @@  __create_hw_context(struct drm_i915_private *dev_priv,
 		struct intel_context *ce = &ctx->__engine[n];
 
 		ce->gem_context = ctx;
+		INIT_LIST_HEAD(&ce->signal_link);
+		INIT_LIST_HEAD(&ce->signals);
 	}
 
 	INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index f6d870b1f73e..e5eca29cd373 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -164,6 +164,8 @@  struct i915_gem_context {
 	struct intel_context {
 		struct i915_gem_context *gem_context;
 		struct intel_engine_cs *active;
+		struct list_head signal_link;
+		struct list_head signals;
 		struct i915_vma *state;
 		struct intel_ring *ring;
 		u32 *lrc_reg_state;
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 5cb3c73f0df5..681203c21b1f 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -530,7 +530,6 @@  static void error_print_engine(struct drm_i915_error_state_buf *m,
 	}
 	err_printf(m, "  seqno: 0x%08x\n", ee->seqno);
 	err_printf(m, "  last_seqno: 0x%08x\n", ee->last_seqno);
-	err_printf(m, "  waiting: %s\n", yesno(ee->waiting));
 	err_printf(m, "  ring->head: 0x%08x\n", ee->cpu_ring_head);
 	err_printf(m, "  ring->tail: 0x%08x\n", ee->cpu_ring_tail);
 	err_printf(m, "  hangcheck stall: %s\n", yesno(ee->hangcheck_stalled));
@@ -807,21 +806,6 @@  static void __err_print_to_sgl(struct drm_i915_error_state_buf *m,
 						    error->epoch);
 		}
 
-		if (IS_ERR(ee->waiters)) {
-			err_printf(m, "%s --- ? waiters [unable to acquire spinlock]\n",
-				   m->i915->engine[i]->name);
-		} else if (ee->num_waiters) {
-			err_printf(m, "%s --- %d waiters\n",
-				   m->i915->engine[i]->name,
-				   ee->num_waiters);
-			for (j = 0; j < ee->num_waiters; j++) {
-				err_printf(m, " seqno 0x%08x for %s [%d]\n",
-					   ee->waiters[j].seqno,
-					   ee->waiters[j].comm,
-					   ee->waiters[j].pid);
-			}
-		}
-
 		print_error_obj(m, m->i915->engine[i],
 				"ringbuffer", ee->ringbuffer);
 
@@ -1003,8 +987,6 @@  void __i915_gpu_state_free(struct kref *error_ref)
 		i915_error_object_free(ee->wa_ctx);
 
 		kfree(ee->requests);
-		if (!IS_ERR_OR_NULL(ee->waiters))
-			kfree(ee->waiters);
 	}
 
 	for (i = 0; i < ARRAY_SIZE(error->active_bo); i++)
@@ -1211,59 +1193,6 @@  static void gen6_record_semaphore_state(struct intel_engine_cs *engine,
 			I915_READ(RING_SYNC_2(engine->mmio_base));
 }
 
-static void error_record_engine_waiters(struct intel_engine_cs *engine,
-					struct drm_i915_error_engine *ee)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct drm_i915_error_waiter *waiter;
-	struct rb_node *rb;
-	int count;
-
-	ee->num_waiters = 0;
-	ee->waiters = NULL;
-
-	if (RB_EMPTY_ROOT(&b->waiters))
-		return;
-
-	if (!spin_trylock_irq(&b->rb_lock)) {
-		ee->waiters = ERR_PTR(-EDEADLK);
-		return;
-	}
-
-	count = 0;
-	for (rb = rb_first(&b->waiters); rb != NULL; rb = rb_next(rb))
-		count++;
-	spin_unlock_irq(&b->rb_lock);
-
-	waiter = NULL;
-	if (count)
-		waiter = kmalloc_array(count,
-				       sizeof(struct drm_i915_error_waiter),
-				       GFP_ATOMIC);
-	if (!waiter)
-		return;
-
-	if (!spin_trylock_irq(&b->rb_lock)) {
-		kfree(waiter);
-		ee->waiters = ERR_PTR(-EDEADLK);
-		return;
-	}
-
-	ee->waiters = waiter;
-	for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
-		struct intel_wait *w = rb_entry(rb, typeof(*w), node);
-
-		strcpy(waiter->comm, w->tsk->comm);
-		waiter->pid = w->tsk->pid;
-		waiter->seqno = w->seqno;
-		waiter++;
-
-		if (++ee->num_waiters == count)
-			break;
-	}
-	spin_unlock_irq(&b->rb_lock);
-}
-
 static void error_record_engine_registers(struct i915_gpu_state *error,
 					  struct intel_engine_cs *engine,
 					  struct drm_i915_error_engine *ee)
@@ -1299,7 +1228,6 @@  static void error_record_engine_registers(struct i915_gpu_state *error,
 
 	intel_engine_get_instdone(engine, &ee->instdone);
 
-	ee->waiting = intel_engine_has_waiter(engine);
 	ee->instpm = I915_READ(RING_INSTPM(engine->mmio_base));
 	ee->acthd = intel_engine_get_active_head(engine);
 	ee->seqno = intel_engine_get_seqno(engine);
@@ -1549,7 +1477,6 @@  static void gem_record_rings(struct i915_gpu_state *error)
 		ee->engine_id = i;
 
 		error_record_engine_registers(error, engine, ee);
-		error_record_engine_waiters(engine, ee);
 		error_record_engine_execlists(engine, ee);
 
 		request = i915_gem_find_active_request(engine);
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.h b/drivers/gpu/drm/i915/i915_gpu_error.h
index 733723e1ea03..cb6a6add543e 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.h
+++ b/drivers/gpu/drm/i915/i915_gpu_error.h
@@ -82,8 +82,6 @@  struct i915_gpu_state {
 		int engine_id;
 		/* Software tracked state */
 		bool idle;
-		bool waiting;
-		int num_waiters;
 		unsigned long hangcheck_timestamp;
 		bool hangcheck_stalled;
 		enum intel_engine_hangcheck_action hangcheck_action;
@@ -161,12 +159,6 @@  struct i915_gpu_state {
 		} *requests, execlist[EXECLIST_MAX_PORTS];
 		unsigned int num_ports;
 
-		struct drm_i915_error_waiter {
-			char comm[TASK_COMM_LEN];
-			pid_t pid;
-			u32 seqno;
-		} *waiters;
-
 		struct {
 			u32 gfx_mode;
 			union {
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 696f5731abf5..914d6446feea 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -28,9 +28,10 @@ 
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
-#include <linux/sysrq.h>
-#include <linux/slab.h>
 #include <linux/circ_buf.h>
+#include <linux/slab.h>
+#include <linux/sysrq.h>
+
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 #include "i915_trace.h"
@@ -1151,67 +1152,6 @@  static void ironlake_rps_change_irq_handler(struct drm_i915_private *dev_priv)
 	return;
 }
 
-static void notify_ring(struct intel_engine_cs *engine)
-{
-	const u32 seqno = intel_engine_get_seqno(engine);
-	struct i915_request *rq = NULL;
-	struct task_struct *tsk = NULL;
-	struct intel_wait *wait;
-
-	if (unlikely(!engine->breadcrumbs.irq_armed))
-		return;
-
-	rcu_read_lock();
-
-	spin_lock(&engine->breadcrumbs.irq_lock);
-	wait = engine->breadcrumbs.irq_wait;
-	if (wait) {
-		/*
-		 * We use a callback from the dma-fence to submit
-		 * requests after waiting on our own requests. To
-		 * ensure minimum delay in queuing the next request to
-		 * hardware, signal the fence now rather than wait for
-		 * the signaler to be woken up. We still wake up the
-		 * waiter in order to handle the irq-seqno coherency
-		 * issues (we may receive the interrupt before the
-		 * seqno is written, see __i915_request_irq_complete())
-		 * and to handle coalescing of multiple seqno updates
-		 * and many waiters.
-		 */
-		if (i915_seqno_passed(seqno, wait->seqno)) {
-			struct i915_request *waiter = wait->request;
-
-			if (waiter &&
-			    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-				      &waiter->fence.flags) &&
-			    intel_wait_check_request(wait, waiter))
-				rq = i915_request_get(waiter);
-
-			tsk = wait->tsk;
-		}
-
-		engine->breadcrumbs.irq_count++;
-	} else {
-		if (engine->breadcrumbs.irq_armed)
-			__intel_engine_disarm_breadcrumbs(engine);
-	}
-	spin_unlock(&engine->breadcrumbs.irq_lock);
-
-	if (rq) {
-		spin_lock(&rq->lock);
-		dma_fence_signal_locked(&rq->fence);
-		GEM_BUG_ON(!i915_request_completed(rq));
-		spin_unlock(&rq->lock);
-
-		i915_request_put(rq);
-	}
-
-	if (tsk && tsk->state & TASK_NORMAL)
-		wake_up_process(tsk);
-
-	rcu_read_unlock();
-}
-
 static void vlv_c0_read(struct drm_i915_private *dev_priv,
 			struct intel_rps_ei *ei)
 {
@@ -1456,20 +1396,20 @@  static void ilk_gt_irq_handler(struct drm_i915_private *dev_priv,
 			       u32 gt_iir)
 {
 	if (gt_iir & GT_RENDER_USER_INTERRUPT)
-		notify_ring(dev_priv->engine[RCS]);
+		intel_engine_breadcrumbs_irq(dev_priv->engine[RCS]);
 	if (gt_iir & ILK_BSD_USER_INTERRUPT)
-		notify_ring(dev_priv->engine[VCS]);
+		intel_engine_breadcrumbs_irq(dev_priv->engine[VCS]);
 }
 
 static void snb_gt_irq_handler(struct drm_i915_private *dev_priv,
 			       u32 gt_iir)
 {
 	if (gt_iir & GT_RENDER_USER_INTERRUPT)
-		notify_ring(dev_priv->engine[RCS]);
+		intel_engine_breadcrumbs_irq(dev_priv->engine[RCS]);
 	if (gt_iir & GT_BSD_USER_INTERRUPT)
-		notify_ring(dev_priv->engine[VCS]);
+		intel_engine_breadcrumbs_irq(dev_priv->engine[VCS]);
 	if (gt_iir & GT_BLT_USER_INTERRUPT)
-		notify_ring(dev_priv->engine[BCS]);
+		intel_engine_breadcrumbs_irq(dev_priv->engine[BCS]);
 
 	if (gt_iir & (GT_BLT_CS_ERROR_INTERRUPT |
 		      GT_BSD_CS_ERROR_INTERRUPT |
@@ -1489,7 +1429,7 @@  gen8_cs_irq_handler(struct intel_engine_cs *engine, u32 iir)
 		tasklet = true;
 
 	if (iir & GT_RENDER_USER_INTERRUPT) {
-		notify_ring(engine);
+		intel_engine_breadcrumbs_irq(engine);
 		tasklet |= USES_GUC_SUBMISSION(engine->i915);
 	}
 
@@ -1835,7 +1775,7 @@  static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir)
 
 	if (HAS_VEBOX(dev_priv)) {
 		if (pm_iir & PM_VEBOX_USER_INTERRUPT)
-			notify_ring(dev_priv->engine[VECS]);
+			intel_engine_breadcrumbs_irq(dev_priv->engine[VECS]);
 
 		if (pm_iir & PM_VEBOX_CS_ERROR_INTERRUPT)
 			DRM_DEBUG("Command parser error, pm_iir 0x%08x\n", pm_iir);
@@ -4258,7 +4198,7 @@  static irqreturn_t i8xx_irq_handler(int irq, void *arg)
 		I915_WRITE16(IIR, iir);
 
 		if (iir & I915_USER_INTERRUPT)
-			notify_ring(dev_priv->engine[RCS]);
+			intel_engine_breadcrumbs_irq(dev_priv->engine[RCS]);
 
 		if (iir & I915_MASTER_ERROR_INTERRUPT)
 			i8xx_error_irq_handler(dev_priv, eir, eir_stuck);
@@ -4366,7 +4306,7 @@  static irqreturn_t i915_irq_handler(int irq, void *arg)
 		I915_WRITE(IIR, iir);
 
 		if (iir & I915_USER_INTERRUPT)
-			notify_ring(dev_priv->engine[RCS]);
+			intel_engine_breadcrumbs_irq(dev_priv->engine[RCS]);
 
 		if (iir & I915_MASTER_ERROR_INTERRUPT)
 			i9xx_error_irq_handler(dev_priv, eir, eir_stuck);
@@ -4511,10 +4451,10 @@  static irqreturn_t i965_irq_handler(int irq, void *arg)
 		I915_WRITE(IIR, iir);
 
 		if (iir & I915_USER_INTERRUPT)
-			notify_ring(dev_priv->engine[RCS]);
+			intel_engine_breadcrumbs_irq(dev_priv->engine[RCS]);
 
 		if (iir & I915_BSD_USER_INTERRUPT)
-			notify_ring(dev_priv->engine[VCS]);
+			intel_engine_breadcrumbs_irq(dev_priv->engine[VCS]);
 
 		if (iir & I915_MASTER_ERROR_INTERRUPT)
 			i9xx_error_irq_handler(dev_priv, eir, eir_stuck);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index c92795ca91a5..e402ec632b45 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -60,7 +60,7 @@  static bool i915_fence_signaled(struct dma_fence *fence)
 
 static bool i915_fence_enable_signaling(struct dma_fence *fence)
 {
-	return intel_engine_enable_signaling(to_request(fence), true);
+	return intel_engine_enable_signaling(to_request(fence));
 }
 
 static signed long i915_fence_wait(struct dma_fence *fence,
@@ -370,9 +370,11 @@  void __i915_request_submit(struct i915_request *request)
 
 	/* We may be recursing from the signal callback of another i915 fence */
 	spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
+	set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags);
 	request->global_seqno = seqno;
-	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags))
-		intel_engine_enable_signaling(request, false);
+	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) &&
+	    !intel_engine_enable_signaling(request))
+		intel_engine_queue_breadcrumbs(engine);
 	spin_unlock(&request->lock);
 
 	engine->emit_breadcrumb(request,
@@ -382,8 +384,6 @@  void __i915_request_submit(struct i915_request *request)
 	move_to_timeline(request, &engine->timeline);
 
 	trace_i915_request_execute(request);
-
-	wake_up_all(&request->execute);
 }
 
 void i915_request_submit(struct i915_request *request)
@@ -427,6 +427,7 @@  void __i915_request_unsubmit(struct i915_request *request)
 	request->global_seqno = 0;
 	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags))
 		intel_engine_cancel_signaling(request);
+	clear_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags);
 	spin_unlock(&request->lock);
 
 	/* Transfer back from the global per-engine timeline to per-context */
@@ -626,13 +627,11 @@  i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
 
 	/* We bump the ref for the fence chain */
 	i915_sw_fence_init(&i915_request_get(rq)->submit, submit_notify);
-	init_waitqueue_head(&rq->execute);
 
 	i915_sched_node_init(&rq->sched);
 
 	/* No zalloc, must clear what we need by hand */
 	rq->global_seqno = 0;
-	rq->signaling.wait.seqno = 0;
 	rq->file_priv = NULL;
 	rq->batch = NULL;
 	rq->capture_list = NULL;
@@ -1023,13 +1022,10 @@  static bool busywait_stop(unsigned long timeout, unsigned int cpu)
 	return this_cpu != cpu;
 }
 
-static bool __i915_spin_request(const struct i915_request *rq,
-				u32 seqno, int state, unsigned long timeout_us)
+static bool __i915_spin_request(const struct i915_request * const rq,
+				int state, unsigned long timeout_us)
 {
-	struct intel_engine_cs *engine = rq->engine;
-	unsigned int irq, cpu;
-
-	GEM_BUG_ON(!seqno);
+	unsigned int cpu;
 
 	/*
 	 * Only wait for the request if we know it is likely to complete.
@@ -1042,7 +1038,7 @@  static bool __i915_spin_request(const struct i915_request *rq,
 	 * it is a fair assumption that it will not complete within our
 	 * relatively short timeout.
 	 */
-	if (!intel_engine_has_started(engine, seqno))
+	if (!i915_request_started(rq))
 		return false;
 
 	/*
@@ -1056,20 +1052,10 @@  static bool __i915_spin_request(const struct i915_request *rq,
 	 * takes to sleep on a request, on the order of a microsecond.
 	 */
 
-	irq = READ_ONCE(engine->breadcrumbs.irq_count);
 	timeout_us += local_clock_us(&cpu);
 	do {
-		if (intel_engine_has_completed(engine, seqno))
-			return seqno == i915_request_global_seqno(rq);
-
-		/*
-		 * Seqno are meant to be ordered *before* the interrupt. If
-		 * we see an interrupt without a corresponding seqno advance,
-		 * assume we won't see one in the near future but require
-		 * the engine->seqno_barrier() to fixup coherency.
-		 */
-		if (READ_ONCE(engine->breadcrumbs.irq_count) != irq)
-			break;
+		if (i915_request_completed(rq))
+			return true;
 
 		if (signal_pending_state(state, current))
 			break;
@@ -1083,6 +1069,18 @@  static bool __i915_spin_request(const struct i915_request *rq,
 	return false;
 }
 
+struct request_wait {
+	struct dma_fence_cb cb;
+	struct task_struct *tsk;
+};
+
+static void request_wait_wake(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+	struct request_wait *wait = container_of(cb, typeof(*wait), cb);
+
+	wake_up_process(wait->tsk);
+}
+
 /**
  * i915_request_wait - wait until execution of request has finished
  * @rq: the request to wait upon
@@ -1108,8 +1106,7 @@  long i915_request_wait(struct i915_request *rq,
 {
 	const int state = flags & I915_WAIT_INTERRUPTIBLE ?
 		TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
-	DEFINE_WAIT_FUNC(exec, default_wake_function);
-	struct intel_wait wait;
+	struct request_wait wait;
 
 	might_sleep();
 	GEM_BUG_ON(timeout < 0);
@@ -1121,47 +1118,24 @@  long i915_request_wait(struct i915_request *rq,
 		return -ETIME;
 
 	trace_i915_request_wait_begin(rq, flags);
-	add_wait_queue(&rq->execute, &exec);
-	intel_wait_init(&wait);
-	if (flags & I915_WAIT_PRIORITY)
-		i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT);
-
-restart:
-	do {
-		set_current_state(state);
-		if (intel_wait_update_request(&wait, rq))
-			break;
-
-		if (signal_pending_state(state, current)) {
-			timeout = -ERESTARTSYS;
-			goto complete;
-		}
 
-		if (!timeout) {
-			timeout = -ETIME;
-			goto complete;
-		}
+	/* Optimistic short spin before touching IRQs */
+	if (__i915_spin_request(rq, state, 5))
+		goto out;
 
-		timeout = io_schedule_timeout(timeout);
-	} while (1);
+	if (flags & I915_WAIT_PRIORITY)
+		i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT);
 
-	GEM_BUG_ON(!intel_wait_has_seqno(&wait));
-	GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit));
+	wait.tsk = current;
+	if (dma_fence_add_callback(&rq->fence, &wait.cb, request_wait_wake))
+		goto out;
 
-	/* Optimistic short spin before touching IRQs */
-	if (__i915_spin_request(rq, wait.seqno, state, 5))
-		goto complete;
+	for (;;) {
+		set_current_state(state);
 
-	set_current_state(state);
-	if (intel_engine_add_wait(rq->engine, &wait))
-		/*
-		 * In order to check that we haven't missed the interrupt
-		 * as we enabled it, we need to kick ourselves to do a
-		 * coherent check on the seqno before we sleep.
-		 */
-		goto wakeup;
+		if (i915_request_completed(rq))
+			break;
 
-	for (;;) {
 		if (signal_pending_state(state, current)) {
 			timeout = -ERESTARTSYS;
 			break;
@@ -1173,33 +1147,13 @@  long i915_request_wait(struct i915_request *rq,
 		}
 
 		timeout = io_schedule_timeout(timeout);
-
-		if (intel_wait_complete(&wait) &&
-		    intel_wait_check_request(&wait, rq))
-			break;
-
-		set_current_state(state);
-
-wakeup:
-		if (i915_request_completed(rq))
-			break;
-
-		/* Only spin if we know the GPU is processing this request */
-		if (__i915_spin_request(rq, wait.seqno, state, 2))
-			break;
-
-		if (!intel_wait_check_request(&wait, rq)) {
-			intel_engine_remove_wait(rq->engine, &wait);
-			goto restart;
-		}
 	}
-
-	intel_engine_remove_wait(rq->engine, &wait);
-complete:
 	__set_current_state(TASK_RUNNING);
-	remove_wait_queue(&rq->execute, &exec);
-	trace_i915_request_wait_end(rq);
 
+	dma_fence_remove_callback(&rq->fence, &wait.cb);
+
+out:
+	trace_i915_request_wait_end(rq);
 	return timeout;
 }
 
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 084d174ba83b..f7741a35f20b 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -38,23 +38,16 @@  struct drm_i915_gem_object;
 struct i915_request;
 struct i915_timeline;
 
-struct intel_wait {
-	struct rb_node node;
-	struct task_struct *tsk;
-	struct i915_request *request;
-	u32 seqno;
-};
-
-struct intel_signal_node {
-	struct intel_wait wait;
-	struct list_head link;
-};
-
 struct i915_capture_list {
 	struct i915_capture_list *next;
 	struct i915_vma *vma;
 };
 
+enum {
+	I915_FENCE_FLAG_ACTIVE = DMA_FENCE_FLAG_USER_BITS,
+	I915_FENCE_FLAG_SIGNAL,
+};
+
 /**
  * Request queue structure.
  *
@@ -97,7 +90,7 @@  struct i915_request {
 	struct intel_context *hw_context;
 	struct intel_ring *ring;
 	struct i915_timeline *timeline;
-	struct intel_signal_node signaling;
+	struct list_head signal_link;
 
 	/*
 	 * The rcu epoch of when this request was allocated. Used to judiciously
@@ -116,7 +109,6 @@  struct i915_request {
 	 */
 	struct i915_sw_fence submit;
 	wait_queue_entry_t submitq;
-	wait_queue_head_t execute;
 
 	/*
 	 * A list of everyone we wait upon, and everyone who waits upon us.
@@ -250,7 +242,7 @@  i915_request_put(struct i915_request *rq)
  * that it has passed the global seqno and the global seqno is unchanged
  * after the read, it is indeed complete).
  */
-static u32
+static inline u32
 i915_request_global_seqno(const struct i915_request *request)
 {
 	return READ_ONCE(request->global_seqno);
diff --git a/drivers/gpu/drm/i915/i915_reset.c b/drivers/gpu/drm/i915/i915_reset.c
index 89d4540ad5e6..4881af83d315 100644
--- a/drivers/gpu/drm/i915/i915_reset.c
+++ b/drivers/gpu/drm/i915/i915_reset.c
@@ -747,18 +747,19 @@  static void reset_restart(struct drm_i915_private *i915)
 
 static void nop_submit_request(struct i915_request *request)
 {
+	struct intel_engine_cs *engine = request->engine;
 	unsigned long flags;
 
 	GEM_TRACE("%s fence %llx:%lld -> -EIO\n",
-		  request->engine->name,
-		  request->fence.context, request->fence.seqno);
+		  engine->name, request->fence.context, request->fence.seqno);
 	dma_fence_set_error(&request->fence, -EIO);
 
-	spin_lock_irqsave(&request->engine->timeline.lock, flags);
+	spin_lock_irqsave(&engine->timeline.lock, flags);
 	__i915_request_submit(request);
 	i915_request_fake_complete(request);
-	intel_engine_write_global_seqno(request->engine, request->global_seqno);
-	spin_unlock_irqrestore(&request->engine->timeline.lock, flags);
+	spin_unlock_irqrestore(&engine->timeline.lock, flags);
+
+	intel_engine_queue_breadcrumbs(engine);
 }
 
 void i915_gem_set_wedged(struct drm_i915_private *i915)
@@ -813,7 +814,7 @@  void i915_gem_set_wedged(struct drm_i915_private *i915)
 
 	for_each_engine(engine, i915, id) {
 		reset_finish_engine(engine);
-		intel_engine_wakeup(engine);
+		intel_engine_signal_breadcrumbs(engine);
 	}
 
 	smp_mb__before_atomic();
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 7b517bf83507..be928bd204d3 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -29,48 +29,135 @@ 
 
 #define task_asleep(tsk) ((tsk)->state & TASK_NORMAL && !(tsk)->on_rq)
 
-static unsigned int __intel_breadcrumbs_wakeup(struct intel_breadcrumbs *b)
+static void irq_enable(struct intel_engine_cs *engine)
+{
+	if (!engine->irq_enable)
+		return;
+
+	/*
+	 * FIXME: Ideally we want this on the API boundary, but for the
+	 * sake of testing with mock breadcrumbs (no HW so unable to
+	 * enable irqs) we place it deep within the bowels, at the point
+	 * of no return.
+	 */
+	GEM_BUG_ON(!intel_irqs_enabled(engine->i915));
+
+	/* Caller disables interrupts */
+	spin_lock(&engine->i915->irq_lock);
+	engine->irq_enable(engine);
+	spin_unlock(&engine->i915->irq_lock);
+}
+
+static void irq_disable(struct intel_engine_cs *engine)
 {
-	struct intel_wait *wait;
-	unsigned int result = 0;
+	if (!engine->irq_disable)
+		return;
+
+	/* Caller disables interrupts */
+	spin_lock(&engine->i915->irq_lock);
+	engine->irq_disable(engine);
+	spin_unlock(&engine->i915->irq_lock);
+}
 
+static void __intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
+{
 	lockdep_assert_held(&b->irq_lock);
 
-	wait = b->irq_wait;
-	if (wait) {
-		/*
-		 * N.B. Since task_asleep() and ttwu are not atomic, the
-		 * waiter may actually go to sleep after the check, causing
-		 * us to suppress a valid wakeup. We prefer to reduce the
-		 * number of false positive missed_breadcrumb() warnings
-		 * at the expense of a few false negatives, as it it easy
-		 * to trigger a false positive under heavy load. Enough
-		 * signal should remain from genuine missed_breadcrumb()
-		 * for us to detect in CI.
-		 */
-		bool was_asleep = task_asleep(wait->tsk);
-
-		result = ENGINE_WAKEUP_WAITER;
-		if (wake_up_process(wait->tsk) && was_asleep)
-			result |= ENGINE_WAKEUP_ASLEEP;
-	}
+	GEM_BUG_ON(!b->irq_enabled);
+	if (!--b->irq_enabled)
+		irq_disable(container_of(b,
+					 struct intel_engine_cs,
+					 breadcrumbs));
 
-	return result;
+	b->irq_armed = false;
 }
 
-unsigned int intel_engine_wakeup(struct intel_engine_cs *engine)
+void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	unsigned long flags;
-	unsigned int result;
 
-	spin_lock_irqsave(&b->irq_lock, flags);
-	result = __intel_breadcrumbs_wakeup(b);
-	spin_unlock_irqrestore(&b->irq_lock, flags);
+	if (!b->irq_armed)
+		return;
+
+	spin_lock_irq(&b->irq_lock);
+	if (b->irq_armed)
+		__intel_breadcrumbs_disarm_irq(b);
+	spin_unlock_irq(&b->irq_lock);
+}
+
+bool intel_engine_breadcrumbs_irq(struct intel_engine_cs *engine)
+{
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+	struct intel_context *ce, *cn;
+	struct i915_request *rq, *rn;
+	LIST_HEAD(signal);
+
+	spin_lock(&b->irq_lock);
+
+	b->irq_fired = true;
+	if (b->irq_armed && list_empty(&b->signalers))
+		__intel_breadcrumbs_disarm_irq(b);
+
+	list_for_each_entry_safe(ce, cn, &b->signalers, signal_link) {
+		GEM_BUG_ON(list_empty(&ce->signals));
+
+		list_for_each_entry_safe(rq, rn, &ce->signals, signal_link) {
+			if (!i915_request_completed(rq))
+				break;
+
+			GEM_BUG_ON(!test_bit(I915_FENCE_FLAG_SIGNAL,
+					     &rq->fence.flags));
+			clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
+
+			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+				     &rq->fence.flags))
+				continue;
+
+			/*
+			 * Queue for execution after dropping the signaling
+			 * spinlock as the callback chain may end adding
+			 * more signalers to the same context or engine.
+			 */
+			i915_request_get(rq);
+			list_add_tail(&rq->signal_link, &signal);
+		}
+
+		if (!list_is_first(&rq->signal_link, &ce->signals)) {
+			__list_del_many(&ce->signals, &rq->signal_link);
+			if (&ce->signals == &rq->signal_link)
+				list_del_init(&ce->signal_link);
+		}
+	}
+
+	spin_unlock(&b->irq_lock);
+
+	list_for_each_entry_safe(rq, rn, &signal, signal_link) {
+		dma_fence_signal(&rq->fence);
+		i915_request_put(rq);
+	}
+
+	return !list_empty(&signal);
+}
+
+bool intel_engine_signal_breadcrumbs(struct intel_engine_cs *engine)
+{
+	bool result;
+
+	local_irq_disable();
+	result = intel_engine_breadcrumbs_irq(engine);
+	local_irq_enable();
 
 	return result;
 }
 
+static void signal_irq_work(struct irq_work *work)
+{
+	struct intel_engine_cs *engine =
+		container_of(work, typeof(*engine), breadcrumbs.irq_work);
+
+	intel_engine_breadcrumbs_irq(engine);
+}
+
 static unsigned long wait_timeout(void)
 {
 	return round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES);
@@ -94,19 +181,15 @@  static void intel_breadcrumbs_hangcheck(struct timer_list *t)
 	struct intel_engine_cs *engine =
 		from_timer(engine, t, breadcrumbs.hangcheck);
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	unsigned int irq_count;
 
 	if (!b->irq_armed)
 		return;
 
-	irq_count = READ_ONCE(b->irq_count);
-	if (b->hangcheck_interrupts != irq_count) {
-		b->hangcheck_interrupts = irq_count;
-		mod_timer(&b->hangcheck, wait_timeout());
-		return;
-	}
+	if (b->irq_fired)
+		goto rearm;
 
-	/* We keep the hangcheck timer alive until we disarm the irq, even
+	/*
+	 * We keep the hangcheck timer alive until we disarm the irq, even
 	 * if there are no waiters at present.
 	 *
 	 * If the waiter was currently running, assume it hasn't had a chance
@@ -118,10 +201,13 @@  static void intel_breadcrumbs_hangcheck(struct timer_list *t)
 	 * but we still have a waiter. Assuming all batches complete within
 	 * DRM_I915_HANGCHECK_JIFFIES [1.5s]!
 	 */
-	if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP) {
+	synchronize_hardirq(engine->i915->drm.irq);
+	if (intel_engine_signal_breadcrumbs(engine)) {
 		missed_breadcrumb(engine);
 		mod_timer(&b->fake_irq, jiffies + 1);
 	} else {
+rearm:
+		b->irq_fired = false;
 		mod_timer(&b->hangcheck, wait_timeout());
 	}
 }
@@ -140,11 +226,7 @@  static void intel_breadcrumbs_fake_irq(struct timer_list *t)
 	 * oldest waiter to do the coherent seqno check.
 	 */
 
-	spin_lock_irq(&b->irq_lock);
-	if (b->irq_armed && !__intel_breadcrumbs_wakeup(b))
-		__intel_engine_disarm_breadcrumbs(engine);
-	spin_unlock_irq(&b->irq_lock);
-	if (!b->irq_armed)
+	if (!intel_engine_signal_breadcrumbs(engine) && !b->irq_armed)
 		return;
 
 	/* If the user has disabled the fake-irq, restore the hangchecking */
@@ -156,51 +238,6 @@  static void intel_breadcrumbs_fake_irq(struct timer_list *t)
 	mod_timer(&b->fake_irq, jiffies + 1);
 }
 
-static void irq_enable(struct intel_engine_cs *engine)
-{
-	if (!engine->irq_enable)
-		return;
-
-	/*
-	 * FIXME: Ideally we want this on the API boundary, but for the
-	 * sake of testing with mock breadcrumbs (no HW so unable to
-	 * enable irqs) we place it deep within the bowels, at the point
-	 * of no return.
-	 */
-	GEM_BUG_ON(!intel_irqs_enabled(engine->i915));
-
-	/* Caller disables interrupts */
-	spin_lock(&engine->i915->irq_lock);
-	engine->irq_enable(engine);
-	spin_unlock(&engine->i915->irq_lock);
-}
-
-static void irq_disable(struct intel_engine_cs *engine)
-{
-	if (!engine->irq_disable)
-		return;
-
-	/* Caller disables interrupts */
-	spin_lock(&engine->i915->irq_lock);
-	engine->irq_disable(engine);
-	spin_unlock(&engine->i915->irq_lock);
-}
-
-void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	lockdep_assert_held(&b->irq_lock);
-	GEM_BUG_ON(b->irq_wait);
-	GEM_BUG_ON(!b->irq_armed);
-
-	GEM_BUG_ON(!b->irq_enabled);
-	if (!--b->irq_enabled)
-		irq_disable(engine);
-
-	b->irq_armed = false;
-}
-
 void intel_engine_pin_breadcrumbs_irq(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
@@ -223,40 +260,6 @@  void intel_engine_unpin_breadcrumbs_irq(struct intel_engine_cs *engine)
 	spin_unlock_irq(&b->irq_lock);
 }
 
-void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct intel_wait *wait, *n;
-
-	if (!b->irq_armed)
-		return;
-
-	/*
-	 * We only disarm the irq when we are idle (all requests completed),
-	 * so if the bottom-half remains asleep, it missed the request
-	 * completion.
-	 */
-	if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP)
-		missed_breadcrumb(engine);
-
-	spin_lock_irq(&b->rb_lock);
-
-	spin_lock(&b->irq_lock);
-	b->irq_wait = NULL;
-	if (b->irq_armed)
-		__intel_engine_disarm_breadcrumbs(engine);
-	spin_unlock(&b->irq_lock);
-
-	rbtree_postorder_for_each_entry_safe(wait, n, &b->waiters, node) {
-		GEM_BUG_ON(!intel_engine_signaled(engine, wait->seqno));
-		RB_CLEAR_NODE(&wait->node);
-		wake_up_process(wait->tsk);
-	}
-	b->waiters = RB_ROOT;
-
-	spin_unlock_irq(&b->rb_lock);
-}
-
 static bool use_fake_irq(const struct intel_breadcrumbs *b)
 {
 	const struct intel_engine_cs *engine =
@@ -272,7 +275,7 @@  static bool use_fake_irq(const struct intel_breadcrumbs *b)
 	 * engine->seqno_barrier(), a timing error that should be transient
 	 * and unlikely to reoccur.
 	 */
-	return READ_ONCE(b->irq_count) == b->hangcheck_interrupts;
+	return !b->irq_fired;
 }
 
 static void enable_fake_irq(struct intel_breadcrumbs *b)
@@ -284,7 +287,7 @@  static void enable_fake_irq(struct intel_breadcrumbs *b)
 		mod_timer(&b->hangcheck, wait_timeout());
 }
 
-static bool __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b)
+static bool __intel_breadcrumbs_arm_irq(struct intel_breadcrumbs *b)
 {
 	struct intel_engine_cs *engine =
 		container_of(b, struct intel_engine_cs, breadcrumbs);
@@ -323,537 +326,132 @@  static bool __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b)
 	return enabled;
 }
 
-static inline struct intel_wait *to_wait(struct rb_node *node)
+void intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
 {
-	return rb_entry(node, struct intel_wait, node);
-}
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
 
-static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b,
-					      struct intel_wait *wait)
-{
-	lockdep_assert_held(&b->rb_lock);
-	GEM_BUG_ON(b->irq_wait == wait);
+	spin_lock_init(&b->irq_lock);
+	INIT_LIST_HEAD(&b->signalers);
 
-	/*
-	 * This request is completed, so remove it from the tree, mark it as
-	 * complete, and *then* wake up the associated task. N.B. when the
-	 * task wakes up, it will find the empty rb_node, discern that it
-	 * has already been removed from the tree and skip the serialisation
-	 * of the b->rb_lock and b->irq_lock. This means that the destruction
-	 * of the intel_wait is not serialised with the interrupt handler
-	 * by the waiter - it must instead be serialised by the caller.
-	 */
-	rb_erase(&wait->node, &b->waiters);
-	RB_CLEAR_NODE(&wait->node);
+	init_irq_work(&b->irq_work, signal_irq_work);
 
-	if (wait->tsk->state != TASK_RUNNING)
-		wake_up_process(wait->tsk); /* implicit smp_wmb() */
+	timer_setup(&b->fake_irq, intel_breadcrumbs_fake_irq, 0);
+	timer_setup(&b->hangcheck, intel_breadcrumbs_hangcheck, 0);
 }
 
-static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine,
-					    struct rb_node *next)
+static void cancel_fake_irq(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
 
-	spin_lock(&b->irq_lock);
-	GEM_BUG_ON(!b->irq_armed);
-	GEM_BUG_ON(!b->irq_wait);
-	b->irq_wait = to_wait(next);
-	spin_unlock(&b->irq_lock);
-
-	/* We always wake up the next waiter that takes over as the bottom-half
-	 * as we may delegate not only the irq-seqno barrier to the next waiter
-	 * but also the task of waking up concurrent waiters.
-	 */
-	if (next)
-		wake_up_process(to_wait(next)->tsk);
+	del_timer_sync(&b->fake_irq); /* may queue b->hangcheck */
+	del_timer_sync(&b->hangcheck);
+	clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
 }
 
-static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
-				    struct intel_wait *wait)
+void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct rb_node **p, *parent, *completed;
-	bool first, armed;
-	u32 seqno;
+	unsigned long flags;
 
-	GEM_BUG_ON(!wait->seqno);
+	spin_lock_irqsave(&b->irq_lock, flags);
 
-	/* Insert the request into the retirement ordered list
-	 * of waiters by walking the rbtree. If we are the oldest
-	 * seqno in the tree (the first to be retired), then
-	 * set ourselves as the bottom-half.
-	 *
-	 * As we descend the tree, prune completed branches since we hold the
-	 * spinlock we know that the first_waiter must be delayed and can
-	 * reduce some of the sequential wake up latency if we take action
-	 * ourselves and wake up the completed tasks in parallel. Also, by
-	 * removing stale elements in the tree, we may be able to reduce the
-	 * ping-pong between the old bottom-half and ourselves as first-waiter.
+	/*
+	 * Leave the fake_irq timer enabled (if it is running), but clear the
+	 * bit so that it turns itself off on its next wake up and goes back
+	 * to the long hangcheck interval if still required.
 	 */
-	armed = false;
-	first = true;
-	parent = NULL;
-	completed = NULL;
-	seqno = intel_engine_get_seqno(engine);
-
-	 /* If the request completed before we managed to grab the spinlock,
-	  * return now before adding ourselves to the rbtree. We let the
-	  * current bottom-half handle any pending wakeups and instead
-	  * try and get out of the way quickly.
-	  */
-	if (i915_seqno_passed(seqno, wait->seqno)) {
-		RB_CLEAR_NODE(&wait->node);
-		return first;
-	}
-
-	p = &b->waiters.rb_node;
-	while (*p) {
-		parent = *p;
-		if (wait->seqno == to_wait(parent)->seqno) {
-			/* We have multiple waiters on the same seqno, select
-			 * the highest priority task (that with the smallest
-			 * task->prio) to serve as the bottom-half for this
-			 * group.
-			 */
-			if (wait->tsk->prio > to_wait(parent)->tsk->prio) {
-				p = &parent->rb_right;
-				first = false;
-			} else {
-				p = &parent->rb_left;
-			}
-		} else if (i915_seqno_passed(wait->seqno,
-					     to_wait(parent)->seqno)) {
-			p = &parent->rb_right;
-			if (i915_seqno_passed(seqno, to_wait(parent)->seqno))
-				completed = parent;
-			else
-				first = false;
-		} else {
-			p = &parent->rb_left;
-		}
-	}
-	rb_link_node(&wait->node, parent, p);
-	rb_insert_color(&wait->node, &b->waiters);
-
-	if (first) {
-		spin_lock(&b->irq_lock);
-		b->irq_wait = wait;
-		/* After assigning ourselves as the new bottom-half, we must
-		 * perform a cursory check to prevent a missed interrupt.
-		 * Either we miss the interrupt whilst programming the hardware,
-		 * or if there was a previous waiter (for a later seqno) they
-		 * may be woken instead of us (due to the inherent race
-		 * in the unlocked read of b->irq_seqno_bh in the irq handler)
-		 * and so we miss the wake up.
-		 */
-		armed = __intel_breadcrumbs_enable_irq(b);
-		spin_unlock(&b->irq_lock);
-	}
-
-	if (completed) {
-		/* Advance the bottom-half (b->irq_wait) before we wake up
-		 * the waiters who may scribble over their intel_wait
-		 * just as the interrupt handler is dereferencing it via
-		 * b->irq_wait.
-		 */
-		if (!first) {
-			struct rb_node *next = rb_next(completed);
-			GEM_BUG_ON(next == &wait->node);
-			__intel_breadcrumbs_next(engine, next);
-		}
-
-		do {
-			struct intel_wait *crumb = to_wait(completed);
-			completed = rb_prev(completed);
-			__intel_breadcrumbs_finish(b, crumb);
-		} while (completed);
-	}
-
-	GEM_BUG_ON(!b->irq_wait);
-	GEM_BUG_ON(!b->irq_armed);
-	GEM_BUG_ON(rb_first(&b->waiters) != &b->irq_wait->node);
-
-	return armed;
-}
-
-bool intel_engine_add_wait(struct intel_engine_cs *engine,
-			   struct intel_wait *wait)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	bool armed;
-
-	spin_lock_irq(&b->rb_lock);
-	armed = __intel_engine_add_wait(engine, wait);
-	spin_unlock_irq(&b->rb_lock);
-	if (armed)
-		return armed;
-
-	/* Make the caller recheck if its request has already started. */
-	return intel_engine_has_started(engine, wait->seqno);
-}
-
-static inline bool chain_wakeup(struct rb_node *rb, int priority)
-{
-	return rb && to_wait(rb)->tsk->prio <= priority;
-}
+	clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
 
-static inline int wakeup_priority(struct intel_breadcrumbs *b,
-				  struct task_struct *tsk)
-{
-	if (tsk == b->signaler)
-		return INT_MIN;
+	if (b->irq_enabled)
+		irq_enable(engine);
 	else
-		return tsk->prio;
-}
-
-static void __intel_engine_remove_wait(struct intel_engine_cs *engine,
-				       struct intel_wait *wait)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	lockdep_assert_held(&b->rb_lock);
-
-	if (RB_EMPTY_NODE(&wait->node))
-		goto out;
-
-	if (b->irq_wait == wait) {
-		const int priority = wakeup_priority(b, wait->tsk);
-		struct rb_node *next;
-
-		/* We are the current bottom-half. Find the next candidate,
-		 * the first waiter in the queue on the remaining oldest
-		 * request. As multiple seqnos may complete in the time it
-		 * takes us to wake up and find the next waiter, we have to
-		 * wake up that waiter for it to perform its own coherent
-		 * completion check.
-		 */
-		next = rb_next(&wait->node);
-		if (chain_wakeup(next, priority)) {
-			/* If the next waiter is already complete,
-			 * wake it up and continue onto the next waiter. So
-			 * if have a small herd, they will wake up in parallel
-			 * rather than sequentially, which should reduce
-			 * the overall latency in waking all the completed
-			 * clients.
-			 *
-			 * However, waking up a chain adds extra latency to
-			 * the first_waiter. This is undesirable if that
-			 * waiter is a high priority task.
-			 */
-			u32 seqno = intel_engine_get_seqno(engine);
-
-			while (i915_seqno_passed(seqno, to_wait(next)->seqno)) {
-				struct rb_node *n = rb_next(next);
-
-				__intel_breadcrumbs_finish(b, to_wait(next));
-				next = n;
-				if (!chain_wakeup(next, priority))
-					break;
-			}
-		}
-
-		__intel_breadcrumbs_next(engine, next);
-	} else {
-		GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);
-	}
-
-	GEM_BUG_ON(RB_EMPTY_NODE(&wait->node));
-	rb_erase(&wait->node, &b->waiters);
-	RB_CLEAR_NODE(&wait->node);
-
-out:
-	GEM_BUG_ON(b->irq_wait == wait);
-	GEM_BUG_ON(rb_first(&b->waiters) !=
-		   (b->irq_wait ? &b->irq_wait->node : NULL));
-}
-
-void intel_engine_remove_wait(struct intel_engine_cs *engine,
-			      struct intel_wait *wait)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	/* Quick check to see if this waiter was already decoupled from
-	 * the tree by the bottom-half to avoid contention on the spinlock
-	 * by the herd.
-	 */
-	if (RB_EMPTY_NODE(&wait->node)) {
-		GEM_BUG_ON(READ_ONCE(b->irq_wait) == wait);
-		return;
-	}
+		irq_disable(engine);
 
-	spin_lock_irq(&b->rb_lock);
-	__intel_engine_remove_wait(engine, wait);
-	spin_unlock_irq(&b->rb_lock);
+	spin_unlock_irqrestore(&b->irq_lock, flags);
 }
 
-static void signaler_set_rtpriority(void)
+void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
 {
-	 struct sched_param param = { .sched_priority = 1 };
-
-	 sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
+	cancel_fake_irq(engine);
 }
 
-static int intel_breadcrumbs_signaler(void *arg)
+bool intel_engine_enable_signaling(struct i915_request *rq)
 {
-	struct intel_engine_cs *engine = arg;
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct i915_request *rq, *n;
-
-	/* Install ourselves with high priority to reduce signalling latency */
-	signaler_set_rtpriority();
-
-	do {
-		bool do_schedule = true;
-		LIST_HEAD(list);
-		u32 seqno;
-
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (list_empty(&b->signals))
-			goto sleep;
-
-		/*
-		 * We are either woken up by the interrupt bottom-half,
-		 * or by a client adding a new signaller. In both cases,
-		 * the GPU seqno may have advanced beyond our oldest signal.
-		 * If it has, propagate the signal, remove the waiter and
-		 * check again with the next oldest signal. Otherwise we
-		 * need to wait for a new interrupt from the GPU or for
-		 * a new client.
-		 */
-		seqno = intel_engine_get_seqno(engine);
-
-		spin_lock_irq(&b->rb_lock);
-		list_for_each_entry_safe(rq, n, &b->signals, signaling.link) {
-			u32 this = rq->signaling.wait.seqno;
-
-			GEM_BUG_ON(!rq->signaling.wait.seqno);
-
-			if (!i915_seqno_passed(seqno, this))
-				break;
+	struct intel_breadcrumbs *b = &rq->engine->breadcrumbs;
 
-			if (likely(this == i915_request_global_seqno(rq))) {
-				__intel_engine_remove_wait(engine,
-							   &rq->signaling.wait);
+	GEM_BUG_ON(test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags));
 
-				rq->signaling.wait.seqno = 0;
-				__list_del_entry(&rq->signaling.link);
-
-				if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-					      &rq->fence.flags)) {
-					list_add_tail(&rq->signaling.link,
-						      &list);
-					i915_request_get(rq);
-				}
-			}
-		}
-		spin_unlock_irq(&b->rb_lock);
-
-		if (!list_empty(&list)) {
-			local_bh_disable();
-			list_for_each_entry_safe(rq, n, &list, signaling.link) {
-				dma_fence_signal(&rq->fence);
-				GEM_BUG_ON(!i915_request_completed(rq));
-				i915_request_put(rq);
-			}
-			local_bh_enable(); /* kick start the tasklets */
+	if (!test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags))
+		return true;
 
-			/*
-			 * If the engine is saturated we may be continually
-			 * processing completed requests. This angers the
-			 * NMI watchdog if we never let anything else
-			 * have access to the CPU. Let's pretend to be nice
-			 * and relinquish the CPU if we burn through the
-			 * entire RT timeslice!
-			 */
-			do_schedule = need_resched();
-		}
+	spin_lock(&b->irq_lock);
+	if (test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags)) {
+		struct intel_context *ce = rq->hw_context;
+		struct i915_request *pos;
 
-		if (unlikely(do_schedule)) {
-sleep:
-			if (kthread_should_park())
-				kthread_parkme();
+		__intel_breadcrumbs_arm_irq(b);
 
-			if (unlikely(kthread_should_stop()))
+		list_for_each_entry_reverse(pos, &ce->signals, signal_link) {
+			if (i915_seqno_passed(rq->fence.seqno,
+					      pos->fence.seqno))
 				break;
-
-			schedule();
 		}
-	} while (1);
-	__set_current_state(TASK_RUNNING);
+		list_add(&rq->signal_link, &pos->signal_link);
 
-	return 0;
-}
+		list_move_tail(&ce->signal_link, &b->signalers);
 
-static void insert_signal(struct intel_breadcrumbs *b,
-			  struct i915_request *request,
-			  const u32 seqno)
-{
-	struct i915_request *iter;
-
-	lockdep_assert_held(&b->rb_lock);
-
-	/*
-	 * A reasonable assumption is that we are called to add signals
-	 * in sequence, as the requests are submitted for execution and
-	 * assigned a global_seqno. This will be the case for the majority
-	 * of internally generated signals (inter-engine signaling).
-	 *
-	 * Out of order waiters triggering random signaling enabling will
-	 * be more problematic, but hopefully rare enough and the list
-	 * small enough that the O(N) insertion sort is not an issue.
-	 */
-
-	list_for_each_entry_reverse(iter, &b->signals, signaling.link)
-		if (i915_seqno_passed(seqno, iter->signaling.wait.seqno))
-			break;
-
-	list_add(&request->signaling.link, &iter->signaling.link);
-}
-
-bool intel_engine_enable_signaling(struct i915_request *request, bool wakeup)
-{
-	struct intel_engine_cs *engine = request->engine;
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct intel_wait *wait = &request->signaling.wait;
-	u32 seqno;
-
-	/*
-	 * Note that we may be called from an interrupt handler on another
-	 * device (e.g. nouveau signaling a fence completion causing us
-	 * to submit a request, and so enable signaling). As such,
-	 * we need to make sure that all other users of b->rb_lock protect
-	 * against interrupts, i.e. use spin_lock_irqsave.
-	 */
-
-	/* locked by dma_fence_enable_sw_signaling() (irqsafe fence->lock) */
-	GEM_BUG_ON(!irqs_disabled());
-	lockdep_assert_held(&request->lock);
-
-	seqno = i915_request_global_seqno(request);
-	if (!seqno) /* will be enabled later upon execution */
-		return true;
-
-	GEM_BUG_ON(wait->seqno);
-	wait->tsk = b->signaler;
-	wait->request = request;
-	wait->seqno = seqno;
-
-	/*
-	 * Add ourselves into the list of waiters, but registering our
-	 * bottom-half as the signaller thread. As per usual, only the oldest
-	 * waiter (not just signaller) is tasked as the bottom-half waking
-	 * up all completed waiters after the user interrupt.
-	 *
-	 * If we are the oldest waiter, enable the irq (after which we
-	 * must double check that the seqno did not complete).
-	 */
-	spin_lock(&b->rb_lock);
-	insert_signal(b, request, seqno);
-	wakeup &= __intel_engine_add_wait(engine, wait);
-	spin_unlock(&b->rb_lock);
-
-	if (wakeup) {
-		wake_up_process(b->signaler);
-		return !intel_wait_complete(wait);
+		set_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
 	}
+	spin_unlock(&b->irq_lock);
 
-	return true;
+	return !i915_request_completed(rq);
 }
 
-void intel_engine_cancel_signaling(struct i915_request *request)
+void intel_engine_cancel_signaling(struct i915_request *rq)
 {
-	struct intel_engine_cs *engine = request->engine;
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	GEM_BUG_ON(!irqs_disabled());
-	lockdep_assert_held(&request->lock);
+	struct intel_breadcrumbs *b = &rq->engine->breadcrumbs;
 
-	if (!READ_ONCE(request->signaling.wait.seqno))
+	if (!test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags))
 		return;
 
-	spin_lock(&b->rb_lock);
-	__intel_engine_remove_wait(engine, &request->signaling.wait);
-	if (fetch_and_zero(&request->signaling.wait.seqno))
-		__list_del_entry(&request->signaling.link);
-	spin_unlock(&b->rb_lock);
-}
-
-int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct task_struct *tsk;
-
-	spin_lock_init(&b->rb_lock);
-	spin_lock_init(&b->irq_lock);
-
-	timer_setup(&b->fake_irq, intel_breadcrumbs_fake_irq, 0);
-	timer_setup(&b->hangcheck, intel_breadcrumbs_hangcheck, 0);
-
-	INIT_LIST_HEAD(&b->signals);
-
-	/* Spawn a thread to provide a common bottom-half for all signals.
-	 * As this is an asynchronous interface we cannot steal the current
-	 * task for handling the bottom-half to the user interrupt, therefore
-	 * we create a thread to do the coherent seqno dance after the
-	 * interrupt and then signal the waitqueue (via the dma-buf/fence).
-	 */
-	tsk = kthread_run(intel_breadcrumbs_signaler, engine,
-			  "i915/signal:%d", engine->id);
-	if (IS_ERR(tsk))
-		return PTR_ERR(tsk);
-
-	b->signaler = tsk;
-
-	return 0;
-}
+	spin_lock(&b->irq_lock);
+	if (test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) {
+		struct intel_context *ce = rq->hw_context;
 
-static void cancel_fake_irq(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+		list_del(&rq->signal_link);
+		if (list_empty(&ce->signals))
+			list_del_init(&ce->signal_link);
 
-	del_timer_sync(&b->fake_irq); /* may queue b->hangcheck */
-	del_timer_sync(&b->hangcheck);
-	clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
+		clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
+	}
+	spin_unlock(&b->irq_lock);
 }
 
-void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
+void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,
+				    struct drm_printer *p)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	unsigned long flags;
+	struct intel_context *ce;
+	struct i915_request *rq;
 
-	spin_lock_irqsave(&b->irq_lock, flags);
-
-	/*
-	 * Leave the fake_irq timer enabled (if it is running), but clear the
-	 * bit so that it turns itself off on its next wake up and goes back
-	 * to the long hangcheck interval if still required.
-	 */
-	clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
-
-	if (b->irq_enabled)
-		irq_enable(engine);
-	else
-		irq_disable(engine);
-
-	spin_unlock_irqrestore(&b->irq_lock, flags);
-}
-
-void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+	if (list_empty(&b->signalers))
+		return;
 
-	/* The engines should be idle and all requests accounted for! */
-	WARN_ON(READ_ONCE(b->irq_wait));
-	WARN_ON(!RB_EMPTY_ROOT(&b->waiters));
-	WARN_ON(!list_empty(&b->signals));
+	drm_printf(p, "Signals:\n");
 
-	if (!IS_ERR_OR_NULL(b->signaler))
-		kthread_stop(b->signaler);
+	spin_lock_irq(&b->irq_lock);
+	list_for_each_entry(ce, &b->signalers, signal_link) {
+		list_for_each_entry(rq, &ce->signals, signal_link) {
+			drm_printf(p, "\t[%llx:%llx%s] @ %dms\n",
+				   rq->fence.context, rq->fence.seqno,
+				   i915_request_completed(rq) ? "!" :
+				   i915_request_started(rq) ? "*" :
+				   "",
+				   jiffies_to_msecs(jiffies - rq->emitted_jiffies));
+		}
+	}
+	spin_unlock_irq(&b->irq_lock);
 
-	cancel_fake_irq(engine);
+	if (test_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings))
+		drm_printf(p, "Fake irq active\n");
 }
-
-#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
-#include "selftests/intel_breadcrumbs.c"
-#endif
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index e49925af6da8..31a614ea0d16 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -458,12 +458,6 @@  int intel_engines_init(struct drm_i915_private *dev_priv)
 void intel_engine_write_global_seqno(struct intel_engine_cs *engine, u32 seqno)
 {
 	intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
-
-	/* After manually advancing the seqno, fake the interrupt in case
-	 * there are any waiters for that seqno.
-	 */
-	intel_engine_wakeup(engine);
-
 	GEM_BUG_ON(intel_engine_get_seqno(engine) != seqno);
 }
 
@@ -667,16 +661,10 @@  int intel_engine_init_common(struct intel_engine_cs *engine)
 		}
 	}
 
-	ret = intel_engine_init_breadcrumbs(engine);
-	if (ret)
-		goto err_unpin_preempt;
+	intel_engine_init_breadcrumbs(engine);
 
 	return 0;
 
-err_unpin_preempt:
-	if (i915->preempt_context)
-		__intel_context_unpin(i915->preempt_context, engine);
-
 err_unpin_kernel:
 	__intel_context_unpin(i915->kernel_context, engine);
 	return ret;
@@ -1236,12 +1224,14 @@  static void print_request(struct drm_printer *m,
 
 	x = print_sched_attr(rq->i915, &rq->sched.attr, buf, x, sizeof(buf));
 
-	drm_printf(m, "%s%x%s [%llx:%llx]%s @ %dms: %s\n",
+	drm_printf(m, "%s%x%s%s [%llx:%llx]%s @ %dms: %s\n",
 		   prefix,
 		   rq->global_seqno,
 		   i915_request_completed(rq) ? "!" :
 		   i915_request_started(rq) ? "*" :
 		   "",
+		   test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+			    &rq->fence.flags) ?  "+" : "",
 		   rq->fence.context, rq->fence.seqno,
 		   buf,
 		   jiffies_to_msecs(jiffies - rq->emitted_jiffies),
@@ -1433,12 +1423,9 @@  void intel_engine_dump(struct intel_engine_cs *engine,
 		       struct drm_printer *m,
 		       const char *header, ...)
 {
-	struct intel_breadcrumbs * const b = &engine->breadcrumbs;
 	struct i915_gpu_error * const error = &engine->i915->gpu_error;
 	struct i915_request *rq;
 	intel_wakeref_t wakeref;
-	unsigned long flags;
-	struct rb_node *rb;
 
 	if (header) {
 		va_list ap;
@@ -1504,21 +1491,12 @@  void intel_engine_dump(struct intel_engine_cs *engine,
 
 	intel_execlists_show_requests(engine, m, print_request, 8);
 
-	spin_lock_irqsave(&b->rb_lock, flags);
-	for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
-		struct intel_wait *w = rb_entry(rb, typeof(*w), node);
-
-		drm_printf(m, "\t%s [%d:%c] waiting for %x\n",
-			   w->tsk->comm, w->tsk->pid,
-			   task_state_to_char(w->tsk),
-			   w->seqno);
-	}
-	spin_unlock_irqrestore(&b->rb_lock, flags);
-
 	drm_printf(m, "HWSP:\n");
 	hexdump(m, engine->status_page.addr, PAGE_SIZE);
 
 	drm_printf(m, "Idle? %s\n", yesno(intel_engine_is_idle(engine)));
+
+	intel_engine_print_breadcrumbs(engine, m);
 }
 
 static u8 user_class_map[] = {
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index bfef3a0113db..6237336518d5 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -482,8 +482,8 @@  static void gen7_xcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
 
 	for (i = 0; i < GEN7_XCS_WA; i++) {
 		*cs++ = MI_STORE_DWORD_INDEX;
-		*cs++ = I915_GEM_HWS_INDEX_ADDR;
-		*cs++ = rq->global_seqno;
+		*cs++ = I915_GEM_HWS_SEQNO_ADDR;
+		*cs++ = rq->fence.seqno;
 	}
 
 	*cs++ = MI_FLUSH_DW;
@@ -733,7 +733,7 @@  static int init_ring_common(struct intel_engine_cs *engine)
 	}
 
 	/* Papering over lost _interrupts_ immediately following the restart */
-	intel_engine_wakeup(engine);
+	intel_engine_signal_breadcrumbs(engine);
 out:
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index e6ec96e0ab56..8b4b7bd529e7 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -5,6 +5,7 @@ 
 #include <drm/drm_util.h>
 
 #include <linux/hashtable.h>
+#include <linux/irq_work.h>
 #include <linux/seqlock.h>
 
 #include "i915_gem_batch_pool.h"
@@ -380,22 +381,19 @@  struct intel_engine_cs {
 	 * the overhead of waking that client is much preferred.
 	 */
 	struct intel_breadcrumbs {
-		spinlock_t irq_lock; /* protects irq_*; irqsafe */
-		struct intel_wait *irq_wait; /* oldest waiter by retirement */
+		spinlock_t irq_lock;
+		struct list_head signalers;
 
-		spinlock_t rb_lock; /* protects the rb and wraps irq_lock */
-		struct rb_root waiters; /* sorted by retirement, priority */
-		struct list_head signals; /* sorted by retirement */
-		struct task_struct *signaler; /* used for fence signalling */
+		struct irq_work irq_work;
 
 		struct timer_list fake_irq; /* used after a missed interrupt */
 		struct timer_list hangcheck; /* detect missed interrupts */
 
 		unsigned int hangcheck_interrupts;
 		unsigned int irq_enabled;
-		unsigned int irq_count;
 
-		bool irq_armed : 1;
+		bool irq_armed;
+		bool irq_fired;
 	} breadcrumbs;
 
 	struct {
@@ -882,83 +880,32 @@  static inline bool intel_engine_has_started(struct intel_engine_cs *engine,
 void intel_engine_get_instdone(struct intel_engine_cs *engine,
 			       struct intel_instdone *instdone);
 
-/* intel_breadcrumbs.c -- user interrupt bottom-half for waiters */
-int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine);
-
-static inline void intel_wait_init(struct intel_wait *wait)
-{
-	wait->tsk = current;
-	wait->request = NULL;
-}
-
-static inline void intel_wait_init_for_seqno(struct intel_wait *wait, u32 seqno)
-{
-	wait->tsk = current;
-	wait->seqno = seqno;
-}
-
-static inline bool intel_wait_has_seqno(const struct intel_wait *wait)
-{
-	return wait->seqno;
-}
-
-static inline bool
-intel_wait_update_seqno(struct intel_wait *wait, u32 seqno)
-{
-	wait->seqno = seqno;
-	return intel_wait_has_seqno(wait);
-}
-
-static inline bool
-intel_wait_update_request(struct intel_wait *wait,
-			  const struct i915_request *rq)
-{
-	return intel_wait_update_seqno(wait, i915_request_global_seqno(rq));
-}
-
-static inline bool
-intel_wait_check_seqno(const struct intel_wait *wait, u32 seqno)
-{
-	return wait->seqno == seqno;
-}
-
-static inline bool
-intel_wait_check_request(const struct intel_wait *wait,
-			 const struct i915_request *rq)
-{
-	return intel_wait_check_seqno(wait, i915_request_global_seqno(rq));
-}
-
-static inline bool intel_wait_complete(const struct intel_wait *wait)
-{
-	return RB_EMPTY_NODE(&wait->node);
-}
+void intel_engine_init_breadcrumbs(struct intel_engine_cs *engine);
+void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine);
 
-bool intel_engine_add_wait(struct intel_engine_cs *engine,
-			   struct intel_wait *wait);
-void intel_engine_remove_wait(struct intel_engine_cs *engine,
-			      struct intel_wait *wait);
-bool intel_engine_enable_signaling(struct i915_request *request, bool wakeup);
+bool intel_engine_enable_signaling(struct i915_request *request);
 void intel_engine_cancel_signaling(struct i915_request *request);
 
-static inline bool intel_engine_has_waiter(const struct intel_engine_cs *engine)
-{
-	return READ_ONCE(engine->breadcrumbs.irq_wait);
-}
-
-unsigned int intel_engine_wakeup(struct intel_engine_cs *engine);
-#define ENGINE_WAKEUP_WAITER BIT(0)
-#define ENGINE_WAKEUP_ASLEEP BIT(1)
-
 void intel_engine_pin_breadcrumbs_irq(struct intel_engine_cs *engine);
 void intel_engine_unpin_breadcrumbs_irq(struct intel_engine_cs *engine);
 
-void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine);
+bool intel_engine_signal_breadcrumbs(struct intel_engine_cs *engine);
 void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine);
 
+static inline void
+intel_engine_queue_breadcrumbs(struct intel_engine_cs *engine)
+{
+	irq_work_queue(&engine->breadcrumbs.irq_work);
+}
+
+bool intel_engine_breadcrumbs_irq(struct intel_engine_cs *engine);
+
 void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine);
 void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine);
 
+void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,
+				    struct drm_printer *p);
+
 static inline u32 *gen8_emit_pipe_control(u32 *batch, u32 flags, u32 offset)
 {
 	memset(batch, 0, 6 * sizeof(u32));
diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
index 4a83a1c6c406..88e5ab586337 100644
--- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
@@ -15,7 +15,6 @@  selftest(scatterlist, scatterlist_mock_selftests)
 selftest(syncmap, i915_syncmap_mock_selftests)
 selftest(uncore, intel_uncore_mock_selftests)
 selftest(engine, intel_engine_cs_mock_selftests)
-selftest(breadcrumbs, intel_breadcrumbs_mock_selftests)
 selftest(timelines, i915_timeline_mock_selftests)
 selftest(requests, i915_request_mock_selftests)
 selftest(objects, i915_gem_object_mock_selftests)
diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 2e14d6d3bad7..48b6159afe64 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -25,8 +25,11 @@ 
 #include <linux/prime_numbers.h>
 
 #include "../i915_selftest.h"
+#include "i915_random.h"
+#include "lib_sw_fence.h"
 
 #include "mock_context.h"
+#include "mock_drm.h"
 #include "mock_gem_device.h"
 
 static int igt_add_request(void *arg)
@@ -246,6 +249,239 @@  static int igt_request_rewind(void *arg)
 	return err;
 }
 
+struct smoketest {
+	struct intel_engine_cs *engine;
+	struct i915_gem_context **contexts;
+	unsigned int ncontexts, max_batch;
+	atomic_long_t num_waits, num_fences;
+	struct i915_request *(*request_alloc)(struct i915_gem_context *,
+					      struct intel_engine_cs *);
+
+};
+
+static struct i915_request *
+__mock_request_alloc(struct i915_gem_context *ctx,
+		     struct intel_engine_cs *engine)
+{
+	return mock_request(engine, ctx, 0);
+}
+
+static struct i915_request *
+__live_request_alloc(struct i915_gem_context *ctx,
+		     struct intel_engine_cs *engine)
+{
+	return i915_request_alloc(engine, ctx);
+}
+
+static int __igt_breadcrumbs_smoketest(void *arg)
+{
+	struct smoketest *t = arg;
+	struct mutex *BKL = &t->engine->i915->drm.struct_mutex;
+	struct i915_request **requests;
+	I915_RND_STATE(prng);
+	const unsigned int total = 4 * t->ncontexts + 1;
+	const unsigned int max_batch = min(t->ncontexts, t->max_batch) - 1;
+	unsigned int num_waits = 0, num_fences = 0;
+	unsigned int *order;
+	int err = 0;
+
+	requests = kmalloc_array(total, sizeof(*requests), GFP_KERNEL);
+	if (!requests)
+		return -ENOMEM;
+
+	order = i915_random_order(total, &prng);
+	if (!order) {
+		err = -ENOMEM;
+		goto out_requests;
+	}
+
+	while (!kthread_should_stop()) {
+		struct i915_sw_fence *submit, *wait;
+		unsigned int n, count;
+
+		submit = heap_fence_create(GFP_KERNEL);
+		if (!submit) {
+			err = -ENOMEM;
+			break;
+		}
+
+		wait = heap_fence_create(GFP_KERNEL);
+		if (!wait) {
+			i915_sw_fence_commit(submit);
+			heap_fence_put(submit);
+			err = ENOMEM;
+			break;
+		}
+
+		i915_random_reorder(order, total, &prng);
+		count = 1 + i915_prandom_u32_max_state(max_batch, &prng);
+
+		for (n = 0; n < count; n++) {
+			struct i915_gem_context *ctx =
+				t->contexts[order[n] % t->ncontexts];
+			struct i915_request *rq;
+
+			mutex_lock(BKL);
+
+			rq = t->request_alloc(ctx, t->engine);
+			if (IS_ERR(rq)) {
+				mutex_unlock(BKL);
+				err = PTR_ERR(rq);
+				count = n;
+				break;
+			}
+
+			err = i915_sw_fence_await_sw_fence_gfp(&rq->submit,
+							       submit,
+							       GFP_KERNEL);
+
+			requests[n] = i915_request_get(rq);
+			i915_request_add(rq);
+
+			mutex_unlock(BKL);
+
+			if (err >= 0)
+				err = i915_sw_fence_await_dma_fence(wait,
+								    &rq->fence,
+								    0,
+								    GFP_KERNEL);
+			if (err < 0) {
+				i915_request_put(rq);
+				count = n;
+				break;
+			}
+		}
+
+		i915_sw_fence_commit(submit);
+		i915_sw_fence_commit(wait);
+
+		if (!wait_event_timeout(wait->wait,
+					i915_sw_fence_done(wait),
+					HZ / 2)) {
+			struct i915_request *rq = requests[count - 1];
+
+			pr_err("waiting for %d fences (last %llx:%lld) on %s timed out!\n",
+			       count,
+			       rq->fence.context, rq->fence.seqno,
+			       t->engine->name);
+			i915_gem_set_wedged(t->engine->i915);
+			GEM_BUG_ON(!i915_request_completed(rq));
+			i915_sw_fence_wait(wait);
+			err = -EIO;
+		}
+
+		for (n = 0; n < count; n++) {
+			struct i915_request *rq = requests[n];
+
+			if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+				      &rq->fence.flags)) {
+				pr_err("%llu:%llu was not signaled!\n",
+				       rq->fence.context, rq->fence.seqno);
+				err = -EINVAL;
+			}
+
+			i915_request_put(rq);
+		}
+
+		heap_fence_put(wait);
+		heap_fence_put(submit);
+
+		if (err < 0)
+			break;
+
+		num_fences += count;
+		num_waits++;
+
+		cond_resched();
+	}
+
+	atomic_long_add(num_fences, &t->num_fences);
+	atomic_long_add(num_waits, &t->num_waits);
+
+	kfree(order);
+out_requests:
+	kfree(requests);
+	return err;
+}
+
+static int mock_breadcrumbs_smoketest(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct smoketest t = {
+		.engine = i915->engine[RCS],
+		.ncontexts = 1024,
+		.max_batch = 1024,
+		.request_alloc = __mock_request_alloc
+	};
+	unsigned int ncpus = num_online_cpus();
+	struct task_struct **threads;
+	unsigned int n;
+	int ret = 0;
+
+	threads = kmalloc_array(ncpus, sizeof(*threads), GFP_KERNEL);
+	if (!threads)
+		return -ENOMEM;
+
+	t.contexts =
+		kmalloc_array(t.ncontexts, sizeof(*t.contexts), GFP_KERNEL);
+	if (!t.contexts) {
+		ret = -ENOMEM;
+		goto out_threads;
+	}
+
+	mutex_lock(&t.engine->i915->drm.struct_mutex);
+	for (n = 0; n < t.ncontexts; n++) {
+		t.contexts[n] = mock_context(t.engine->i915, "mock");
+		if (!t.contexts[n]) {
+			ret = -ENOMEM;
+			goto out_contexts;
+		}
+	}
+
+	for (n = 0; n < ncpus; n++) {
+		threads[n] = kthread_run(__igt_breadcrumbs_smoketest,
+					 &t, "igt/%d", n);
+		if (IS_ERR(threads[n])) {
+			ret = PTR_ERR(threads[n]);
+			ncpus = n;
+			break;
+		}
+
+		get_task_struct(threads[n]);
+	}
+	mutex_unlock(&t.engine->i915->drm.struct_mutex);
+
+	msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
+
+	for (n = 0; n < ncpus; n++) {
+		int err;
+
+		err = kthread_stop(threads[n]);
+		if (err < 0 && !ret)
+			ret = err;
+
+		put_task_struct(threads[n]);
+	}
+	pr_info("Completed %lu waits for %lu fence across %d cpus\n",
+		atomic_long_read(&t.num_waits),
+		atomic_long_read(&t.num_fences),
+		ncpus);
+
+	mutex_lock(&t.engine->i915->drm.struct_mutex);
+out_contexts:
+	for (n = 0; n < t.ncontexts; n++) {
+		if (!t.contexts[n])
+			break;
+		mock_context_close(t.contexts[n]);
+	}
+	mutex_unlock(&t.engine->i915->drm.struct_mutex);
+	kfree(t.contexts);
+out_threads:
+	kfree(threads);
+
+	return ret;
+}
+
 int i915_request_mock_selftests(void)
 {
 	static const struct i915_subtest tests[] = {
@@ -253,6 +489,7 @@  int i915_request_mock_selftests(void)
 		SUBTEST(igt_wait_request),
 		SUBTEST(igt_fence_wait),
 		SUBTEST(igt_request_rewind),
+		SUBTEST(mock_breadcrumbs_smoketest),
 	};
 	struct drm_i915_private *i915;
 	intel_wakeref_t wakeref;
@@ -872,6 +1109,166 @@  static int live_sequential_engines(void *arg)
 	return err;
 }
 
+static int
+max_batches(struct i915_gem_context *ctx, struct intel_engine_cs *engine)
+{
+	struct i915_request *rq;
+	int ret;
+
+	/*
+	 * Before execlists, all contexts share the same ringbuffer. With
+	 * execlists, each context/engine has a separate ringbuffer and
+	 * for the purposes of this test, inexhaustible.
+	 *
+	 * For the global ringbuffer though, we have to be very careful
+	 * that we do not wrap while preventing the execution of requests
+	 * with a unsignaled fence.
+	 */
+	if (HAS_EXECLISTS(ctx->i915))
+		return INT_MAX;
+
+	rq = i915_request_alloc(engine, ctx);
+	if (IS_ERR(rq)) {
+		ret = PTR_ERR(rq);
+	} else {
+		int sz;
+
+		ret = rq->ring->size - rq->reserved_space;
+		i915_request_add(rq);
+
+		sz = rq->ring->emit - rq->head;
+		if (sz < 0)
+			sz += rq->ring->size;
+		ret /= sz;
+		ret /= 2; /* leave half spare, in case of emergency! */
+
+		/* One ring interleaved between requests from all cpus */
+		ret /= num_online_cpus() + 1;
+	}
+
+	return ret;
+}
+
+static int live_breadcrumbs_smoketest(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct smoketest t[I915_NUM_ENGINES];
+	unsigned int ncpus = num_online_cpus();
+	unsigned long num_waits, num_fences;
+	struct intel_engine_cs *engine;
+	struct task_struct **threads;
+	enum intel_engine_id id;
+	intel_wakeref_t wakeref;
+	struct drm_file *file;
+	struct live_test live;
+	unsigned int n;
+	int ret = 0;
+
+	wakeref = intel_runtime_pm_get(i915);
+
+	file = mock_file(i915);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto out_rpm;
+	}
+
+	threads = kcalloc(ncpus * I915_NUM_ENGINES,
+			  sizeof(*threads),
+			  GFP_KERNEL);
+	if (!threads)
+		return -ENOMEM;
+
+	memset(&t[0], 0, sizeof(t[0]));
+	t[0].request_alloc = __live_request_alloc;
+	t[0].ncontexts = 64;
+	t[0].contexts = kmalloc_array(t[0].ncontexts,
+				      sizeof(*t[0].contexts),
+				      GFP_KERNEL);
+	if (!t[0].contexts) {
+		ret = -ENOMEM;
+		goto out_threads;
+	}
+
+	mutex_lock(&i915->drm.struct_mutex);
+	for (n = 0; n < t[0].ncontexts; n++) {
+		t[0].contexts[n] = live_context(i915, file);
+		if (!t[0].contexts[n]) {
+			ret = -ENOMEM;
+			goto out_contexts;
+		}
+	}
+
+	ret = begin_live_test(&live, i915, __func__, "");
+	if (ret)
+		goto out_contexts;
+
+	for_each_engine(engine, i915, id) {
+		t[id] = t[0];
+		t[id].engine = engine;
+		t[id].max_batch = max_batches(t[0].contexts[0], engine);
+		if (t[id].max_batch < 0) {
+			ret = t[id].max_batch;
+			goto out_flush;
+		}
+		pr_debug("Limiting batches to %d requests on %s\n",
+			 t[id].max_batch, engine->name);
+
+		for (n = 0; n < ncpus; n++) {
+			struct task_struct *tsk;
+
+			tsk = kthread_run(__igt_breadcrumbs_smoketest,
+					  &t[id], "igt/%d.%d", id, n);
+			if (IS_ERR(tsk)) {
+				ret = PTR_ERR(tsk);
+				goto out_flush;
+			}
+
+			get_task_struct(tsk);
+			threads[id * ncpus + n] = tsk;
+		}
+	}
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
+
+out_flush:
+	num_waits = 0;
+	num_fences = 0;
+	for_each_engine(engine, i915, id) {
+		for (n = 0; n < ncpus; n++) {
+			struct task_struct *tsk = threads[id * ncpus + n];
+			int err;
+
+			if (!tsk)
+				continue;
+
+			err = kthread_stop(tsk);
+			if (err < 0 && !ret)
+				ret = err;
+
+			put_task_struct(tsk);
+		}
+
+		num_waits += atomic_long_read(&t[id].num_waits);
+		num_fences += atomic_long_read(&t[id].num_fences);
+	}
+	pr_info("Completed %lu waits for %lu fence across %d engines and %d cpus\n",
+		num_waits, num_fences, RUNTIME_INFO(i915)->num_rings, ncpus);
+
+	mutex_lock(&i915->drm.struct_mutex);
+	ret = end_live_test(&live) ?: ret;
+out_contexts:
+	mutex_unlock(&i915->drm.struct_mutex);
+	kfree(t[0].contexts);
+out_threads:
+	kfree(threads);
+	mock_file_free(i915, file);
+out_rpm:
+	intel_runtime_pm_put(i915, wakeref);
+
+	return ret;
+}
+
 int i915_request_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
@@ -879,6 +1276,7 @@  int i915_request_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(live_all_engines),
 		SUBTEST(live_sequential_engines),
 		SUBTEST(live_empty_request),
+		SUBTEST(live_breadcrumbs_smoketest),
 	};
 
 	if (i915_terminally_wedged(&i915->gpu_error))
diff --git a/drivers/gpu/drm/i915/selftests/igt_spinner.c b/drivers/gpu/drm/i915/selftests/igt_spinner.c
index 0e70df0230b8..9ebd9225684e 100644
--- a/drivers/gpu/drm/i915/selftests/igt_spinner.c
+++ b/drivers/gpu/drm/i915/selftests/igt_spinner.c
@@ -185,11 +185,6 @@  void igt_spinner_fini(struct igt_spinner *spin)
 
 bool igt_wait_for_spinner(struct igt_spinner *spin, struct i915_request *rq)
 {
-	if (!wait_event_timeout(rq->execute,
-				READ_ONCE(rq->global_seqno),
-				msecs_to_jiffies(10)))
-		return false;
-
 	return !(wait_for_us(i915_seqno_passed(hws_seqno(spin, rq),
 					       rq->fence.seqno),
 			     10) &&
diff --git a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c b/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
deleted file mode 100644
index f03b407fdbe2..000000000000
--- a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
+++ /dev/null
@@ -1,470 +0,0 @@ 
-/*
- * Copyright © 2016 Intel Corporation
- *
- * Permission is hereby granted, free of charge, to any person obtaining a
- * copy of this software and associated documentation files (the "Software"),
- * to deal in the Software without restriction, including without limitation
- * the rights to use, copy, modify, merge, publish, distribute, sublicense,
- * and/or sell copies of the Software, and to permit persons to whom the
- * Software is furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice (including the next
- * paragraph) shall be included in all copies or substantial portions of the
- * Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
- * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
- * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
- * IN THE SOFTWARE.
- *
- */
-
-#include "../i915_selftest.h"
-#include "i915_random.h"
-
-#include "mock_gem_device.h"
-#include "mock_engine.h"
-
-static int check_rbtree(struct intel_engine_cs *engine,
-			const unsigned long *bitmap,
-			const struct intel_wait *waiters,
-			const int count)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-	struct rb_node *rb;
-	int n;
-
-	if (&b->irq_wait->node != rb_first(&b->waiters)) {
-		pr_err("First waiter does not match first element of wait-tree\n");
-		return -EINVAL;
-	}
-
-	n = find_first_bit(bitmap, count);
-	for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
-		struct intel_wait *w = container_of(rb, typeof(*w), node);
-		int idx = w - waiters;
-
-		if (!test_bit(idx, bitmap)) {
-			pr_err("waiter[%d, seqno=%d] removed but still in wait-tree\n",
-			       idx, w->seqno);
-			return -EINVAL;
-		}
-
-		if (n != idx) {
-			pr_err("waiter[%d, seqno=%d] does not match expected next element in tree [%d]\n",
-			       idx, w->seqno, n);
-			return -EINVAL;
-		}
-
-		n = find_next_bit(bitmap, count, n + 1);
-	}
-
-	return 0;
-}
-
-static int check_completion(struct intel_engine_cs *engine,
-			    const unsigned long *bitmap,
-			    const struct intel_wait *waiters,
-			    const int count)
-{
-	int n;
-
-	for (n = 0; n < count; n++) {
-		if (intel_wait_complete(&waiters[n]) != !!test_bit(n, bitmap))
-			continue;
-
-		pr_err("waiter[%d, seqno=%d] is %s, but expected %s\n",
-		       n, waiters[n].seqno,
-		       intel_wait_complete(&waiters[n]) ? "complete" : "active",
-		       test_bit(n, bitmap) ? "active" : "complete");
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-static int check_rbtree_empty(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	if (b->irq_wait) {
-		pr_err("Empty breadcrumbs still has a waiter\n");
-		return -EINVAL;
-	}
-
-	if (!RB_EMPTY_ROOT(&b->waiters)) {
-		pr_err("Empty breadcrumbs, but wait-tree not empty\n");
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-static int igt_random_insert_remove(void *arg)
-{
-	const u32 seqno_bias = 0x1000;
-	I915_RND_STATE(prng);
-	struct intel_engine_cs *engine = arg;
-	struct intel_wait *waiters;
-	const int count = 4096;
-	unsigned int *order;
-	unsigned long *bitmap;
-	int err = -ENOMEM;
-	int n;
-
-	mock_engine_reset(engine);
-
-	waiters = kvmalloc_array(count, sizeof(*waiters), GFP_KERNEL);
-	if (!waiters)
-		goto out_engines;
-
-	bitmap = kcalloc(DIV_ROUND_UP(count, BITS_PER_LONG), sizeof(*bitmap),
-			 GFP_KERNEL);
-	if (!bitmap)
-		goto out_waiters;
-
-	order = i915_random_order(count, &prng);
-	if (!order)
-		goto out_bitmap;
-
-	for (n = 0; n < count; n++)
-		intel_wait_init_for_seqno(&waiters[n], seqno_bias + n);
-
-	err = check_rbtree(engine, bitmap, waiters, count);
-	if (err)
-		goto out_order;
-
-	/* Add and remove waiters into the rbtree in random order. At each
-	 * step, we verify that the rbtree is correctly ordered.
-	 */
-	for (n = 0; n < count; n++) {
-		int i = order[n];
-
-		intel_engine_add_wait(engine, &waiters[i]);
-		__set_bit(i, bitmap);
-
-		err = check_rbtree(engine, bitmap, waiters, count);
-		if (err)
-			goto out_order;
-	}
-
-	i915_random_reorder(order, count, &prng);
-	for (n = 0; n < count; n++) {
-		int i = order[n];
-
-		intel_engine_remove_wait(engine, &waiters[i]);
-		__clear_bit(i, bitmap);
-
-		err = check_rbtree(engine, bitmap, waiters, count);
-		if (err)
-			goto out_order;
-	}
-
-	err = check_rbtree_empty(engine);
-out_order:
-	kfree(order);
-out_bitmap:
-	kfree(bitmap);
-out_waiters:
-	kvfree(waiters);
-out_engines:
-	mock_engine_flush(engine);
-	return err;
-}
-
-static int igt_insert_complete(void *arg)
-{
-	const u32 seqno_bias = 0x1000;
-	struct intel_engine_cs *engine = arg;
-	struct intel_wait *waiters;
-	const int count = 4096;
-	unsigned long *bitmap;
-	int err = -ENOMEM;
-	int n, m;
-
-	mock_engine_reset(engine);
-
-	waiters = kvmalloc_array(count, sizeof(*waiters), GFP_KERNEL);
-	if (!waiters)
-		goto out_engines;
-
-	bitmap = kcalloc(DIV_ROUND_UP(count, BITS_PER_LONG), sizeof(*bitmap),
-			 GFP_KERNEL);
-	if (!bitmap)
-		goto out_waiters;
-
-	for (n = 0; n < count; n++) {
-		intel_wait_init_for_seqno(&waiters[n], n + seqno_bias);
-		intel_engine_add_wait(engine, &waiters[n]);
-		__set_bit(n, bitmap);
-	}
-	err = check_rbtree(engine, bitmap, waiters, count);
-	if (err)
-		goto out_bitmap;
-
-	/* On each step, we advance the seqno so that several waiters are then
-	 * complete (we increase the seqno by increasingly larger values to
-	 * retire more and more waiters at once). All retired waiters should
-	 * be woken and removed from the rbtree, and so that we check.
-	 */
-	for (n = 0; n < count; n = m) {
-		int seqno = 2 * n;
-
-		GEM_BUG_ON(find_first_bit(bitmap, count) != n);
-
-		if (intel_wait_complete(&waiters[n])) {
-			pr_err("waiter[%d, seqno=%d] completed too early\n",
-			       n, waiters[n].seqno);
-			err = -EINVAL;
-			goto out_bitmap;
-		}
-
-		/* complete the following waiters */
-		mock_seqno_advance(engine, seqno + seqno_bias);
-		for (m = n; m <= seqno; m++) {
-			if (m == count)
-				break;
-
-			GEM_BUG_ON(!test_bit(m, bitmap));
-			__clear_bit(m, bitmap);
-		}
-
-		intel_engine_remove_wait(engine, &waiters[n]);
-		RB_CLEAR_NODE(&waiters[n].node);
-
-		err = check_rbtree(engine, bitmap, waiters, count);
-		if (err) {
-			pr_err("rbtree corrupt after seqno advance to %d\n",
-			       seqno + seqno_bias);
-			goto out_bitmap;
-		}
-
-		err = check_completion(engine, bitmap, waiters, count);
-		if (err) {
-			pr_err("completions after seqno advance to %d failed\n",
-			       seqno + seqno_bias);
-			goto out_bitmap;
-		}
-	}
-
-	err = check_rbtree_empty(engine);
-out_bitmap:
-	kfree(bitmap);
-out_waiters:
-	kvfree(waiters);
-out_engines:
-	mock_engine_flush(engine);
-	return err;
-}
-
-struct igt_wakeup {
-	struct task_struct *tsk;
-	atomic_t *ready, *set, *done;
-	struct intel_engine_cs *engine;
-	unsigned long flags;
-#define STOP 0
-#define IDLE 1
-	wait_queue_head_t *wq;
-	u32 seqno;
-};
-
-static bool wait_for_ready(struct igt_wakeup *w)
-{
-	DEFINE_WAIT(ready);
-
-	set_bit(IDLE, &w->flags);
-	if (atomic_dec_and_test(w->done))
-		wake_up_var(w->done);
-
-	if (test_bit(STOP, &w->flags))
-		goto out;
-
-	for (;;) {
-		prepare_to_wait(w->wq, &ready, TASK_INTERRUPTIBLE);
-		if (atomic_read(w->ready) == 0)
-			break;
-
-		schedule();
-	}
-	finish_wait(w->wq, &ready);
-
-out:
-	clear_bit(IDLE, &w->flags);
-	if (atomic_dec_and_test(w->set))
-		wake_up_var(w->set);
-
-	return !test_bit(STOP, &w->flags);
-}
-
-static int igt_wakeup_thread(void *arg)
-{
-	struct igt_wakeup *w = arg;
-	struct intel_wait wait;
-
-	while (wait_for_ready(w)) {
-		GEM_BUG_ON(kthread_should_stop());
-
-		intel_wait_init_for_seqno(&wait, w->seqno);
-		intel_engine_add_wait(w->engine, &wait);
-		for (;;) {
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			if (i915_seqno_passed(intel_engine_get_seqno(w->engine),
-					      w->seqno))
-				break;
-
-			if (test_bit(STOP, &w->flags)) /* emergency escape */
-				break;
-
-			schedule();
-		}
-		intel_engine_remove_wait(w->engine, &wait);
-		__set_current_state(TASK_RUNNING);
-	}
-
-	return 0;
-}
-
-static void igt_wake_all_sync(atomic_t *ready,
-			      atomic_t *set,
-			      atomic_t *done,
-			      wait_queue_head_t *wq,
-			      int count)
-{
-	atomic_set(set, count);
-	atomic_set(ready, 0);
-	wake_up_all(wq);
-
-	wait_var_event(set, !atomic_read(set));
-	atomic_set(ready, count);
-	atomic_set(done, count);
-}
-
-static int igt_wakeup(void *arg)
-{
-	I915_RND_STATE(prng);
-	struct intel_engine_cs *engine = arg;
-	struct igt_wakeup *waiters;
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
-	const int count = 4096;
-	const u32 max_seqno = count / 4;
-	atomic_t ready, set, done;
-	int err = -ENOMEM;
-	int n, step;
-
-	mock_engine_reset(engine);
-
-	waiters = kvmalloc_array(count, sizeof(*waiters), GFP_KERNEL);
-	if (!waiters)
-		goto out_engines;
-
-	/* Create a large number of threads, each waiting on a random seqno.
-	 * Multiple waiters will be waiting for the same seqno.
-	 */
-	atomic_set(&ready, count);
-	for (n = 0; n < count; n++) {
-		waiters[n].wq = &wq;
-		waiters[n].ready = &ready;
-		waiters[n].set = &set;
-		waiters[n].done = &done;
-		waiters[n].engine = engine;
-		waiters[n].flags = BIT(IDLE);
-
-		waiters[n].tsk = kthread_run(igt_wakeup_thread, &waiters[n],
-					     "i915/igt:%d", n);
-		if (IS_ERR(waiters[n].tsk))
-			goto out_waiters;
-
-		get_task_struct(waiters[n].tsk);
-	}
-
-	for (step = 1; step <= max_seqno; step <<= 1) {
-		u32 seqno;
-
-		/* The waiter threads start paused as we assign them a random
-		 * seqno and reset the engine. Once the engine is reset,
-		 * we signal that the threads may begin their wait upon their
-		 * seqno.
-		 */
-		for (n = 0; n < count; n++) {
-			GEM_BUG_ON(!test_bit(IDLE, &waiters[n].flags));
-			waiters[n].seqno =
-				1 + prandom_u32_state(&prng) % max_seqno;
-		}
-		mock_seqno_advance(engine, 0);
-		igt_wake_all_sync(&ready, &set, &done, &wq, count);
-
-		/* Simulate the GPU doing chunks of work, with one or more
-		 * seqno appearing to finish at the same time. A random number
-		 * of threads will be waiting upon the update and hopefully be
-		 * woken.
-		 */
-		for (seqno = 1; seqno <= max_seqno + step; seqno += step) {
-			usleep_range(50, 500);
-			mock_seqno_advance(engine, seqno);
-		}
-		GEM_BUG_ON(intel_engine_get_seqno(engine) < 1 + max_seqno);
-
-		/* With the seqno now beyond any of the waiting threads, they
-		 * should all be woken, see that they are complete and signal
-		 * that they are ready for the next test. We wait until all
-		 * threads are complete and waiting for us (i.e. not a seqno).
-		 */
-		if (!wait_var_event_timeout(&done,
-					    !atomic_read(&done), 10 * HZ)) {
-			pr_err("Timed out waiting for %d remaining waiters\n",
-			       atomic_read(&done));
-			err = -ETIMEDOUT;
-			break;
-		}
-
-		err = check_rbtree_empty(engine);
-		if (err)
-			break;
-	}
-
-out_waiters:
-	for (n = 0; n < count; n++) {
-		if (IS_ERR(waiters[n].tsk))
-			break;
-
-		set_bit(STOP, &waiters[n].flags);
-	}
-	mock_seqno_advance(engine, INT_MAX); /* wakeup any broken waiters */
-	igt_wake_all_sync(&ready, &set, &done, &wq, n);
-
-	for (n = 0; n < count; n++) {
-		if (IS_ERR(waiters[n].tsk))
-			break;
-
-		kthread_stop(waiters[n].tsk);
-		put_task_struct(waiters[n].tsk);
-	}
-
-	kvfree(waiters);
-out_engines:
-	mock_engine_flush(engine);
-	return err;
-}
-
-int intel_breadcrumbs_mock_selftests(void)
-{
-	static const struct i915_subtest tests[] = {
-		SUBTEST(igt_random_insert_remove),
-		SUBTEST(igt_insert_complete),
-		SUBTEST(igt_wakeup),
-	};
-	struct drm_i915_private *i915;
-	int err;
-
-	i915 = mock_gem_device();
-	if (!i915)
-		return -ENOMEM;
-
-	err = i915_subtests(tests, i915->engine[RCS]);
-	drm_dev_put(&i915->drm);
-
-	return err;
-}
diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
index 4809874ab28c..4e8c3008dc84 100644
--- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
@@ -1127,7 +1127,7 @@  static int __igt_reset_evict_vma(struct drm_i915_private *i915,
 
 	wait_for_completion(&arg.completion);
 
-	if (wait_for(waitqueue_active(&rq->execute), 10)) {
+	if (wait_for(!list_empty(&rq->fence.cb_list), 10)) {
 		struct drm_printer p = drm_info_printer(i915->drm.dev);
 
 		pr_err("igt/evict_vma kthread did not wait\n");
diff --git a/drivers/gpu/drm/i915/selftests/lib_sw_fence.c b/drivers/gpu/drm/i915/selftests/lib_sw_fence.c
index b26f07b55d86..2bfa72c1654b 100644
--- a/drivers/gpu/drm/i915/selftests/lib_sw_fence.c
+++ b/drivers/gpu/drm/i915/selftests/lib_sw_fence.c
@@ -76,3 +76,57 @@  void timed_fence_fini(struct timed_fence *tf)
 	destroy_timer_on_stack(&tf->timer);
 	i915_sw_fence_fini(&tf->fence);
 }
+
+struct heap_fence {
+	struct i915_sw_fence fence;
+	union {
+		struct kref ref;
+		struct rcu_head rcu;
+	};
+};
+
+static int __i915_sw_fence_call
+heap_fence_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
+{
+	struct heap_fence *h = container_of(fence, typeof(*h), fence);
+
+	switch (state) {
+	case FENCE_COMPLETE:
+		break;
+
+	case FENCE_FREE:
+		heap_fence_put(&h->fence);
+	}
+
+	return NOTIFY_DONE;
+}
+
+struct i915_sw_fence *heap_fence_create(gfp_t gfp)
+{
+	struct heap_fence *h;
+
+	h = kmalloc(sizeof(*h), gfp);
+	if (!h)
+		return NULL;
+
+	i915_sw_fence_init(&h->fence, heap_fence_notify);
+	refcount_set(&h->ref.refcount, 2);
+
+	return &h->fence;
+}
+
+static void heap_fence_release(struct kref *ref)
+{
+	struct heap_fence *h = container_of(ref, typeof(*h), ref);
+
+	i915_sw_fence_fini(&h->fence);
+
+	kfree_rcu(h, rcu);
+}
+
+void heap_fence_put(struct i915_sw_fence *fence)
+{
+	struct heap_fence *h = container_of(fence, typeof(*h), fence);
+
+	kref_put(&h->ref, heap_fence_release);
+}
diff --git a/drivers/gpu/drm/i915/selftests/lib_sw_fence.h b/drivers/gpu/drm/i915/selftests/lib_sw_fence.h
index 474aafb92ae1..1f9927e10f3a 100644
--- a/drivers/gpu/drm/i915/selftests/lib_sw_fence.h
+++ b/drivers/gpu/drm/i915/selftests/lib_sw_fence.h
@@ -39,4 +39,7 @@  struct timed_fence {
 void timed_fence_init(struct timed_fence *tf, unsigned long expires);
 void timed_fence_fini(struct timed_fence *tf);
 
+struct i915_sw_fence *heap_fence_create(gfp_t gfp);
+void heap_fence_put(struct i915_sw_fence *fence);
+
 #endif /* _LIB_SW_FENCE_H_ */
diff --git a/drivers/gpu/drm/i915/selftests/mock_context.c b/drivers/gpu/drm/i915/selftests/mock_context.c
index d937bdff26f9..e4db9a31b510 100644
--- a/drivers/gpu/drm/i915/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/selftests/mock_context.c
@@ -49,6 +49,8 @@  mock_context(struct drm_i915_private *i915,
 		struct intel_context *ce = &ctx->__engine[n];
 
 		ce->gem_context = ctx;
+		INIT_LIST_HEAD(&ce->signal_link);
+		INIT_LIST_HEAD(&ce->signals);
 	}
 
 	ret = i915_gem_context_pin_hw_id(ctx);
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index b4b61056b227..c1cd8b27b32a 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -75,25 +75,27 @@  static struct mock_request *first_request(struct mock_engine *engine)
 					link);
 }
 
-static void advance(struct mock_engine *engine,
-		    struct mock_request *request)
+static void advance(struct mock_request *request)
 {
 	list_del_init(&request->link);
 	i915_request_fake_complete(&request->base);
-	mock_seqno_advance(&engine->base, request->base.global_seqno);
+	intel_engine_write_global_seqno(request->base.engine,
+					request->base.global_seqno);
+	intel_engine_queue_breadcrumbs(request->base.engine);
 }
 
 static void hw_delay_complete(struct timer_list *t)
 {
 	struct mock_engine *engine = from_timer(engine, t, hw_delay);
 	struct mock_request *request;
+	unsigned long flags;
 
-	spin_lock(&engine->hw_lock);
+	spin_lock_irqsave(&engine->hw_lock, flags);
 
 	/* Timer fired, first request is complete */
 	request = first_request(engine);
 	if (request)
-		advance(engine, request);
+		advance(request);
 
 	/*
 	 * Also immediately signal any subsequent 0-delay requests, but
@@ -105,10 +107,10 @@  static void hw_delay_complete(struct timer_list *t)
 			break;
 		}
 
-		advance(engine, request);
+		advance(request);
 	}
 
-	spin_unlock(&engine->hw_lock);
+	spin_unlock_irqrestore(&engine->hw_lock, flags);
 }
 
 static void mock_context_unpin(struct intel_context *ce)
@@ -179,19 +181,20 @@  static void mock_submit_request(struct i915_request *request)
 	struct mock_request *mock = container_of(request, typeof(*mock), base);
 	struct mock_engine *engine =
 		container_of(request->engine, typeof(*engine), base);
+	unsigned long flags;
 
 	i915_request_submit(request);
 	GEM_BUG_ON(!request->global_seqno);
 
-	spin_lock_irq(&engine->hw_lock);
+	spin_lock_irqsave(&engine->hw_lock, flags);
 	list_add_tail(&mock->link, &engine->hw_queue);
 	if (mock->link.prev == &engine->hw_queue) {
 		if (mock->delay)
 			mod_timer(&engine->hw_delay, jiffies + mock->delay);
 		else
-			advance(engine, mock);
+			advance(mock);
 	}
-	spin_unlock_irq(&engine->hw_lock);
+	spin_unlock_irqrestore(&engine->hw_lock, flags);
 }
 
 struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
@@ -255,12 +258,13 @@  void mock_engine_flush(struct intel_engine_cs *engine)
 
 	spin_lock_irq(&mock->hw_lock);
 	list_for_each_entry_safe(request, rn, &mock->hw_queue, link)
-		advance(mock, request);
+		advance(request);
 	spin_unlock_irq(&mock->hw_lock);
 }
 
 void mock_engine_reset(struct intel_engine_cs *engine)
 {
+	intel_engine_write_global_seqno(engine, 0);
 }
 
 void mock_engine_free(struct intel_engine_cs *engine)
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.h b/drivers/gpu/drm/i915/selftests/mock_engine.h
index 133d0c21790d..b9cc3a245f16 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.h
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.h
@@ -46,10 +46,4 @@  void mock_engine_flush(struct intel_engine_cs *engine);
 void mock_engine_reset(struct intel_engine_cs *engine);
 void mock_engine_free(struct intel_engine_cs *engine);
 
-static inline void mock_seqno_advance(struct intel_engine_cs *engine, u32 seqno)
-{
-	intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
-	intel_engine_wakeup(engine);
-}
-
 #endif /* !__MOCK_ENGINE_H__ */