From b58cf6eab7b9193543d563bc31ab578f0df73649 Mon Sep 17 00:00:00 2001
From: Domi <Domiii@users.noreply.github.com>
Date: Tue, 18 Jul 2023 18:57:46 +0200
Subject: [PATCH] RUN-2365: Allowed Divergence + Leaking agent_group_schedulers
 (#826)

---
 .../main_thread/agent_group_scheduler_impl.cc | 22 +++++++++++++------
 .../main_thread/main_thread_scheduler_impl.cc | 16 ++++++++------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/third_party/blink/renderer/platform/scheduler/main_thread/agent_group_scheduler_impl.cc b/third_party/blink/renderer/platform/scheduler/main_thread/agent_group_scheduler_impl.cc
index f81f2ebf6c5ddb..bb39caf40e8b3e 100644
--- a/third_party/blink/renderer/platform/scheduler/main_thread/agent_group_scheduler_impl.cc
+++ b/third_party/blink/renderer/platform/scheduler/main_thread/agent_group_scheduler_impl.cc
@@ -63,6 +63,14 @@ AgentGroupSchedulerImpl::~AgentGroupSchedulerImpl() {
 
   default_task_queue_->DetachFromMainThreadScheduler();
   compositor_task_queue_->DetachFromMainThreadScheduler();
+
+  // Leak this when removed during GC and if it contains agents.
+  // See https://linear.app/replay/issue/RUN-2056#comment-460ec1ff
+  if (recordreplay::AreEventsDisallowed(
+          "MainThreadSchedulerImpl::RemoveAgentGroupScheduler") &&
+      agents_->size())
+    return;
+
   main_thread_scheduler_.RemoveAgentGroupScheduler(this);
 }
 
@@ -137,16 +145,16 @@ void AgentGroupSchedulerImpl::RemoveAgent(Agent* agent) {
 }
 
 void AgentGroupSchedulerImpl::PerformMicrotaskCheckpoint() {
-  recordreplay::Assert(
-      "[RUN-2056-2298] AgentGroupSchedulerImpl::PerformMicrotaskCheckpoint "
-      "Start %d %d",
-      RecordReplayId(), (int)agents_->size());
-
   for (Agent* agent : *agents_) {
+    // WARN: Don't Assert on AgentGroupSchedulerImpl on its own since they are
+    // allowed to diverge. However, agents are not allowed to diverge.
+    // See https://linear.app/replay/issue/RUN-2056#comment-460ec1ff
+    recordreplay::Assert(
+        "[RUN-2056-2365] AgentGroupSchedulerImpl::PerformMicrotaskCheckpoint "
+        "%d %d %d",
+        RecordReplayId(), (int)agents_->size(), agent->RecordReplayId());
     agent->PerformMicrotaskCheckpoint();
   }
-
-  recordreplay::Assert("[RUN-2056-2211] AgentGroupSchedulerImpl::PerformMicrotaskCheckpoint Done");
 }
 
 }  // namespace scheduler
diff --git a/third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl.cc b/third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl.cc
index 502426482ccfc0..b63e55145f7350 100644
--- a/third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl.cc
+++ b/third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl.cc
@@ -1121,10 +1121,14 @@ void MainThreadSchedulerImpl::SetHaveSeenABlockingGestureForTesting(
 void MainThreadSchedulerImpl::PerformMicrotaskCheckpoint() {
   // This will fallback to execute the microtask checkpoint for the
   // default EventLoop for the isolate.
+
+  // Warn: Don't assert on `agent_group_schedulers.size()` since they are
+  // allowed to diverge.
+  // See https://linear.app/replay/issue/RUN-2056#comment-460ec1ff
   recordreplay::Assert(
-      "[RUN-2056-2298] MainThreadSchedulerImpl::PerformMicrotaskCheckpoint %d %d %u",
-      recordreplay::PointerId(this), !!isolate(),
-      main_thread_only().agent_group_schedulers.size());
+      "[RUN-2056-2365] MainThreadSchedulerImpl::PerformMicrotaskCheckpoint A %d %d",
+      recordreplay::PointerId(this), !!isolate());
+
   if (isolate())
     EventLoop::PerformIsolateGlobalMicrotasksCheckpoint(isolate());
   // Perform a microtask checkpoint for each AgentSchedulingGroup. This
@@ -1137,7 +1141,8 @@ void MainThreadSchedulerImpl::PerformMicrotaskCheckpoint() {
     agent_group_scheduler->PerformMicrotaskCheckpoint();
   }
   recordreplay::Assert(
-      "[RUN-2056] MainThreadSchedulerImpl::PerformMicrotaskCheckpoint Done");
+      "[RUN-2056-2365] MainThreadSchedulerImpl::PerformMicrotaskCheckpoint "
+      "B");
 }
 
 // static
@@ -2165,9 +2170,6 @@ void MainThreadSchedulerImpl::RemoveAgentGroupScheduler(
     AgentGroupSchedulerImpl* agent_group_scheduler) {
   DCHECK(main_thread_only().agent_group_schedulers.Contains(
       agent_group_scheduler));
-  recordreplay::Assert(
-      "[RUN-2056-2316] MainThreadSchedulerImpl::RemoveAgentGroupScheduler %d",
-      agent_group_scheduler->RecordReplayId());
   main_thread_only().agent_group_schedulers.erase(agent_group_scheduler);
 }