From ed260e8cae329a0c077e91ff76d104ee197fb7fd Mon Sep 17 00:00:00 2001
From: Thomas Schatzl <tschatzl@openjdk.org>
Date: Thu, 21 Aug 2025 09:37:34 +0000
Subject: [PATCH] 8365026: G1: Initialization should start a "full" new
 collection set

Reviewed-by: ayang, kbarrett
---
 src/hotspot/share/gc/g1/g1CollectedHeap.cpp  | 2 ++
 src/hotspot/share/gc/g1/g1ConcurrentMark.cpp | 3 ++-
 src/hotspot/share/gc/g1/g1Policy.cpp         | 4 ----
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
index e964ecefb18..ed08d43bbbe 100644
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
@@ -1487,6 +1487,8 @@ jint G1CollectedHeap::initialize() {
 
   _collection_set.initialize(max_num_regions());
 
+  start_new_collection_set();
+
   allocation_failure_injector()->reset();
 
   CPUTimeCounters::create_counter(CPUTimeGroups::CPUTimeType::gc_parallel_workers);
diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
index 210d78098b3..237704c12a8 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
@@ -1962,7 +1962,8 @@ public:
 };
 
 void G1ConcurrentMark::verify_no_collection_set_oops() {
-  assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
+  assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
+         "should be at a safepoint or initializing");
   if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
     return;
   }
diff --git a/src/hotspot/share/gc/g1/g1Policy.cpp b/src/hotspot/share/gc/g1/g1Policy.cpp
index bb54d344ca0..53f0a7bf7a6 100644
--- a/src/hotspot/share/gc/g1/g1Policy.cpp
+++ b/src/hotspot/share/gc/g1/g1Policy.cpp
@@ -97,10 +97,6 @@ void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 
   update_young_length_bounds();
-
-  // We immediately start allocating regions placing them in the collection set.
-  // Initialize the collection set info.
-  _collection_set->start_incremental_building();
 }
 
 void G1Policy::record_young_gc_pause_start() {