!i915_request_completed(rq));
 
                        GEM_BUG_ON(i915_request_is_active(w));
-                       if (list_empty(&w->sched.link))
-                               continue; /* Not yet submitted; unready */
+                       if (!i915_request_is_ready(w))
+                               continue;
 
                        if (rq_prio(w) < rq_prio(rq))
                                continue;
        }
 }
 
+static void __execlists_hold(struct i915_request *rq)
+{
+       LIST_HEAD(list);
+
+       do {
+               struct i915_dependency *p;
+
+               if (i915_request_is_active(rq))
+                       __i915_request_unsubmit(rq);
+
+               RQ_TRACE(rq, "on hold\n");
+               clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
+               list_move_tail(&rq->sched.link, &rq->engine->active.hold);
+               i915_request_set_hold(rq);
+
+               list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
+                       struct i915_request *w =
+                               container_of(p->waiter, typeof(*w), sched);
+
+                       /* Leave semaphores spinning on the other engines */
+                       if (w->engine != rq->engine)
+                               continue;
+
+                       if (!i915_request_is_ready(w))
+                               continue;
+
+                       if (i915_request_completed(w))
+                               continue;
+
+                       if (i915_request_on_hold(rq))
+                               continue;
+
+                       list_move_tail(&w->sched.link, &list);
+               }
+
+               rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
+       } while (rq);
+}
+
+__maybe_unused
+static void execlists_hold(struct intel_engine_cs *engine,
+                          struct i915_request *rq)
+{
+       spin_lock_irq(&engine->active.lock);
+
+       /*
+        * Transfer this request onto the hold queue to prevent it
+        * being resumbitted to HW (and potentially completed) before we have
+        * released it. Since we may have already submitted following
+        * requests, we need to remove those as well.
+        */
+       GEM_BUG_ON(i915_request_on_hold(rq));
+       GEM_BUG_ON(rq->engine != engine);
+       __execlists_hold(rq);
+
+       spin_unlock_irq(&engine->active.lock);
+}
+
+static bool hold_request(const struct i915_request *rq)
+{
+       struct i915_dependency *p;
+
+       /*
+        * If one of our ancestors is on hold, we must also be on hold,
+        * otherwise we will bypass it and execute before it.
+        */
+       list_for_each_entry(p, &rq->sched.signalers_list, signal_link) {
+               const struct i915_request *s =
+                       container_of(p->signaler, typeof(*s), sched);
+
+               if (s->engine != rq->engine)
+                       continue;
+
+               if (i915_request_on_hold(s))
+                       return true;
+       }
+
+       return false;
+}
+
+static void __execlists_unhold(struct i915_request *rq)
+{
+       LIST_HEAD(list);
+
+       do {
+               struct i915_dependency *p;
+
+               GEM_BUG_ON(!i915_request_on_hold(rq));
+               GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit));
+
+               i915_request_clear_hold(rq);
+               list_move_tail(&rq->sched.link,
+                              i915_sched_lookup_priolist(rq->engine,
+                                                         rq_prio(rq)));
+               set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
+               RQ_TRACE(rq, "hold release\n");
+
+               /* Also release any children on this engine that are ready */
+               list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
+                       struct i915_request *w =
+                               container_of(p->waiter, typeof(*w), sched);
+
+                       if (w->engine != rq->engine)
+                               continue;
+
+                       if (!i915_request_on_hold(rq))
+                               continue;
+
+                       /* Check that no other parents are also on hold */
+                       if (hold_request(rq))
+                               continue;
+
+                       list_move_tail(&w->sched.link, &list);
+               }
+
+               rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
+       } while (rq);
+}
+
+__maybe_unused
+static void execlists_unhold(struct intel_engine_cs *engine,
+                            struct i915_request *rq)
+{
+       spin_lock_irq(&engine->active.lock);
+
+       /*
+        * Move this request back to the priority queue, and all of its
+        * children and grandchildren that were suspended along with it.
+        */
+       __execlists_unhold(rq);
+
+       if (rq_prio(rq) > engine->execlists.queue_priority_hint) {
+               engine->execlists.queue_priority_hint = rq_prio(rq);
+               tasklet_hi_schedule(&engine->execlists.tasklet);
+       }
+
+       spin_unlock_irq(&engine->active.lock);
+}
+
 static noinline void preempt_reset(struct intel_engine_cs *engine)
 {
        const unsigned int bit = I915_RESET_ENGINE + engine->id;
        __submit_queue_imm(engine);
 }
 
+static bool ancestor_on_hold(const struct intel_engine_cs *engine,
+                            const struct i915_request *rq)
+{
+       GEM_BUG_ON(i915_request_on_hold(rq));
+       return !list_empty(&engine->active.hold) && hold_request(rq);
+}
+
 static void execlists_submit_request(struct i915_request *request)
 {
        struct intel_engine_cs *engine = request->engine;
        /* Will be called from irq-context when using foreign fences. */
        spin_lock_irqsave(&engine->active.lock, flags);
 
-       queue_request(engine, request);
+       if (unlikely(ancestor_on_hold(engine, request))) {
+               list_add_tail(&request->sched.link, &engine->active.hold);
+               i915_request_set_hold(request);
+       } else {
+               queue_request(engine, request);
 
-       GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
-       GEM_BUG_ON(list_empty(&request->sched.link));
+               GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
+               GEM_BUG_ON(list_empty(&request->sched.link));
 
-       submit_queue(engine, request);
+               submit_queue(engine, request);
+       }
 
        spin_unlock_irqrestore(&engine->active.lock, flags);
 }
                i915_priolist_free(p);
        }
 
+       /* On-hold requests will be flushed to timeline upon their release */
+       list_for_each_entry(rq, &engine->active.hold, sched.link)
+               mark_eio(rq);
+
        /* Cancel all attached virtual engines */
        while ((rb = rb_first_cached(&execlists->virtual))) {
                struct virtual_engine *ve =
 
        return live_unlite_restore(arg, I915_USER_PRIORITY(I915_PRIORITY_MAX));
 }
 
+static int live_hold_reset(void *arg)
+{
+       struct intel_gt *gt = arg;
+       struct intel_engine_cs *engine;
+       enum intel_engine_id id;
+       struct igt_spinner spin;
+       int err = 0;
+
+       /*
+        * In order to support offline error capture for fast preempt reset,
+        * we need to decouple the guilty request and ensure that it and its
+        * descendents are not executed while the capture is in progress.
+        */
+
+       if (!intel_has_reset_engine(gt))
+               return 0;
+
+       if (igt_spinner_init(&spin, gt))
+               return -ENOMEM;
+
+       for_each_engine(engine, gt, id) {
+               struct intel_context *ce;
+               unsigned long heartbeat;
+               struct i915_request *rq;
+
+               ce = intel_context_create(engine);
+               if (IS_ERR(ce)) {
+                       err = PTR_ERR(ce);
+                       break;
+               }
+
+               engine_heartbeat_disable(engine, &heartbeat);
+
+               rq = igt_spinner_create_request(&spin, ce, MI_ARB_CHECK);
+               if (IS_ERR(rq)) {
+                       err = PTR_ERR(rq);
+                       goto out;
+               }
+               i915_request_add(rq);
+
+               if (!igt_wait_for_spinner(&spin, rq)) {
+                       intel_gt_set_wedged(gt);
+                       err = -ETIME;
+                       goto out;
+               }
+
+               /* We have our request executing, now remove it and reset */
+
+               if (test_and_set_bit(I915_RESET_ENGINE + id,
+                                    >->reset.flags)) {
+                       spin_unlock_irq(&engine->active.lock);
+                       intel_gt_set_wedged(gt);
+                       err = -EBUSY;
+                       goto out;
+               }
+               tasklet_disable(&engine->execlists.tasklet);
+
+               engine->execlists.tasklet.func(engine->execlists.tasklet.data);
+               GEM_BUG_ON(execlists_active(&engine->execlists) != rq);
+
+               execlists_hold(engine, rq);
+               GEM_BUG_ON(!i915_request_on_hold(rq));
+
+               intel_engine_reset(engine, NULL);
+               GEM_BUG_ON(rq->fence.error != -EIO);
+
+               tasklet_enable(&engine->execlists.tasklet);
+               clear_and_wake_up_bit(I915_RESET_ENGINE + id,
+                                     >->reset.flags);
+
+               /* Check that we do not resubmit the held request */
+               i915_request_get(rq);
+               if (!i915_request_wait(rq, 0, HZ / 5)) {
+                       pr_err("%s: on hold request completed!\n",
+                              engine->name);
+                       i915_request_put(rq);
+                       err = -EIO;
+                       goto out;
+               }
+               GEM_BUG_ON(!i915_request_on_hold(rq));
+
+               /* But is resubmitted on release */
+               execlists_unhold(engine, rq);
+               if (i915_request_wait(rq, 0, HZ / 5) < 0) {
+                       pr_err("%s: held request did not complete!\n",
+                              engine->name);
+                       intel_gt_set_wedged(gt);
+                       err = -ETIME;
+               }
+               i915_request_put(rq);
+
+out:
+               engine_heartbeat_enable(engine, heartbeat);
+               intel_context_put(ce);
+               if (err)
+                       break;
+       }
+
+       igt_spinner_fini(&spin);
+       return err;
+}
+
 static int
 emit_semaphore_chain(struct i915_request *rq, struct i915_vma *vma, int idx)
 {
                SUBTEST(live_sanitycheck),
                SUBTEST(live_unlite_switch),
                SUBTEST(live_unlite_preempt),
+               SUBTEST(live_hold_reset),
                SUBTEST(live_timeslice_preempt),
                SUBTEST(live_timeslice_queue),
                SUBTEST(live_busywait_preempt),
 
         */
        I915_FENCE_FLAG_SIGNAL,
 
+       /*
+        * I915_FENCE_FLAG_HOLD - this request is currently on hold
+        *
+        * This request has been suspended, pending an ongoing investigation.
+        */
+       I915_FENCE_FLAG_HOLD,
+
        /*
         * I915_FENCE_FLAG_NOPREEMPT - this request should not be preempted
         *
        return __i915_request_has_started(rq);
 }
 
+/**
+ * i915_request_is_running - check if the request is ready for execution
+ * @rq: the request
+ *
+ * Upon construction, the request is instructed to wait upon various
+ * signals before it is ready to be executed by the HW. That is, we do
+ * not want to start execution and read data before it is written. In practice,
+ * this is controlled with a mixture of interrupts and semaphores. Once
+ * the submit fence is completed, the backend scheduler will place the
+ * request into its queue and from there submit it for execution. So we
+ * can detect when a request is eligible for execution (and is under control
+ * of the scheduler) by querying where it is in any of the scheduler's lists.
+ *
+ * Returns true if the request is ready for execution (it may be inflight),
+ * false otherwise.
+ */
+static inline bool i915_request_is_ready(const struct i915_request *rq)
+{
+       return !list_empty(&rq->sched.link);
+}
+
 static inline bool i915_request_completed(const struct i915_request *rq)
 {
        if (i915_request_signaled(rq))
        return unlikely(test_bit(I915_FENCE_FLAG_SENTINEL, &rq->fence.flags));
 }
 
+static inline bool i915_request_on_hold(const struct i915_request *rq)
+{
+       return unlikely(test_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags));
+}
+
+static inline void i915_request_set_hold(struct i915_request *rq)
+{
+       set_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);
+}
+
+static inline void i915_request_clear_hold(struct i915_request *rq)
+{
+       clear_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);
+}
+
 static inline struct intel_timeline *
 i915_request_timeline(struct i915_request *rq)
 {