From 1d8e7a2a1429330ea3d03ad4b216bcfb9d6629b7 Mon Sep 17 00:00:00 2001
From: William Kemper <kemperw@amazon.com>
Date: Thu, 15 Jan 2026 16:33:59 -0800
Subject: [PATCH] Go even lower, don't check for safepoint when taking the
 locks

---
 src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp | 6 +++---
 src/hotspot/share/gc/shenandoah/shenandoahController.cpp    | 4 ++--
 src/hotspot/share/gc/shenandoah/shenandoahController.hpp    | 4 ++--
 .../gc/shenandoah/shenandoahGenerationalControlThread.cpp   | 6 +++---
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp b/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp
index 72258a575c9..737bb82a3e2 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp
@@ -44,7 +44,7 @@ ShenandoahControlThread::ShenandoahControlThread() :
   ShenandoahController(),
   _requested_gc_cause(GCCause::_no_gc),
   _degen_point(ShenandoahGC::_degenerated_outside_cycle),
-  _control_lock(LOCK_RANK, "ShenandoahGCRequest_lock", true) {
+  _control_lock(LOCK_RANK - 1, "ShenandoahControl_lock", true) {
   set_name("Shenandoah Control Thread");
   create_and_start();
 }
@@ -380,7 +380,7 @@ void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
   // opportunities for cleanup that were made available before the caller
   // requested the GC.
 
-  MonitorLocker ml(&_gc_waiters_lock);
+  MonitorLocker ml(&_gc_waiters_lock, Mutex::_no_safepoint_check_flag);
   size_t current_gc_id = get_gc_id();
   size_t required_gc_id = current_gc_id + 1;
   while (current_gc_id < required_gc_id && !should_terminate()) {
@@ -392,6 +392,6 @@ void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
 
 void ShenandoahControlThread::notify_gc_waiters() {
   _gc_requested.unset();
-  MonitorLocker ml(&_gc_waiters_lock);
+  MonitorLocker ml(&_gc_waiters_lock, Mutex::_no_safepoint_check_flag);
   ml.notify_all();
 }
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahController.cpp b/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
index 220f3df8d4f..fa4c30e9a41 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
@@ -51,7 +51,7 @@ void ShenandoahController::handle_alloc_failure(const ShenandoahAllocRequest& re
   }
 
   if (block) {
-    MonitorLocker ml(&_alloc_failure_waiters_lock);
+    MonitorLocker ml(&_alloc_failure_waiters_lock, Mutex::_no_safepoint_check_flag);
     while (!should_terminate() && ShenandoahCollectorPolicy::is_allocation_failure(heap->cancelled_cause())) {
       ml.wait();
     }
@@ -70,6 +70,6 @@ void ShenandoahController::handle_alloc_failure_evac(size_t words) {
 }
 
 void ShenandoahController::notify_alloc_failure_waiters() {
-  MonitorLocker ml(&_alloc_failure_waiters_lock);
+  MonitorLocker ml(&_alloc_failure_waiters_lock, Mutex::_no_safepoint_check_flag);
   ml.notify_all();
 }
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahController.hpp b/src/hotspot/share/gc/shenandoah/shenandoahController.hpp
index deca9644174..bbd83dad13d 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahController.hpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahController.hpp
@@ -56,8 +56,8 @@ protected:
 public:
   ShenandoahController():
     _gc_id(0),
-    _alloc_failure_waiters_lock(LOCK_RANK, "ShenandoahAllocFailureGC_lock", true),
-    _gc_waiters_lock(LOCK_RANK, "ShenandoahRequestedGC_lock", true)
+    _alloc_failure_waiters_lock(LOCK_RANK, "ShenandoahAllocFailureWaiters_lock", true),
+    _gc_waiters_lock(LOCK_RANK, "ShenandoahGCWaiters_lock", true)
   { }
 
   // Request a collection cycle. This handles "explicit" gc requests
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp b/src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp
index 0cdcda29fe6..d7c0de42cb3 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp
@@ -47,7 +47,7 @@
 #include "utilities/events.hpp"
 
 ShenandoahGenerationalControlThread::ShenandoahGenerationalControlThread() :
-  _control_lock(LOCK_RANK, "ShenandoahGCRequest_lock", true),
+  _control_lock(LOCK_RANK - 1, "ShenandoahControl_lock", true),
   _requested_gc_cause(GCCause::_no_gc),
   _requested_generation(nullptr),
   _gc_mode(none),
@@ -759,7 +759,7 @@ void ShenandoahGenerationalControlThread::handle_requested_gc(GCCause::Cause cau
   // opportunities for cleanup that were made available before the caller
   // requested the GC.
 
-  MonitorLocker ml(&_gc_waiters_lock);
+  MonitorLocker ml(&_gc_waiters_lock, Mutex::_no_safepoint_check_flag);
   size_t current_gc_id = get_gc_id();
   const size_t required_gc_id = current_gc_id + 1;
   while (current_gc_id < required_gc_id && !should_terminate()) {
@@ -771,7 +771,7 @@ void ShenandoahGenerationalControlThread::handle_requested_gc(GCCause::Cause cau
 }
 
 void ShenandoahGenerationalControlThread::notify_gc_waiters() {
-  MonitorLocker ml(&_gc_waiters_lock);
+  MonitorLocker ml(&_gc_waiters_lock, Mutex::_no_safepoint_check_flag);
   ml.notify_all();
 }