openjdk · fbredber · Sep 29, 2025 · Oct 1, 2025
diff --git a/src/hotspot/cpu/aarch64/globalDefinitions_aarch64.hpp b/src/hotspot/cpu/aarch64/globalDefinitions_aarch64.hpp
@@ -35,8 +35,6 @@ const bool CCallingConventionRequiresIntsAsLongs = false;
 
 #define SUPPORTS_NATIVE_CX8
 
-#define SUPPORT_MONITOR_COUNT
-
 // Aarch64 was not originally defined to be multi-copy-atomic, but now
 // is.  See: "Simplifying ARM Concurrency: Multicopy-atomic Axiomatic
 // and Operational Models for ARMv8"

diff --git a/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp b/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp
@@ -5630,38 +5630,6 @@ void MacroAssembler::tlab_allocate(Register obj,
   bs->tlab_allocate(this, obj, var_size_in_bytes, con_size_in_bytes, t1, t2, slow_case);
 }
 
-void MacroAssembler::inc_held_monitor_count(Register tmp) {
-  Address dst(rthread, JavaThread::held_monitor_count_offset());
-#ifdef ASSERT
-  ldr(tmp, dst);
-  increment(tmp);
-  str(tmp, dst);
-  Label ok;
-  tbz(tmp, 63, ok);
-  STOP("assert(held monitor count underflow)");
-  should_not_reach_here();
-  bind(ok);
-#else
-  increment(dst);
-#endif
-}
-
-void MacroAssembler::dec_held_monitor_count(Register tmp) {
-  Address dst(rthread, JavaThread::held_monitor_count_offset());
-#ifdef ASSERT
-  ldr(tmp, dst);
-  decrement(tmp);
-  str(tmp, dst);
-  Label ok;
-  tbz(tmp, 63, ok);
-  STOP("assert(held monitor count underflow)");
-  should_not_reach_here();
-  bind(ok);
-#else
-  decrement(dst);
-#endif
-}
-
 void MacroAssembler::verify_tlab() {
 #ifdef ASSERT
   if (UseTLAB && VerifyOops) {

diff --git a/src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp b/src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp
@@ -983,9 +983,6 @@ class MacroAssembler: public Assembler {
   void push_cont_fastpath(Register java_thread = rthread);
   void pop_cont_fastpath(Register java_thread = rthread);
 
-  void inc_held_monitor_count(Register tmp);
-  void dec_held_monitor_count(Register tmp);
-
   // Round up to a power of two
   void round_to(Register reg, int modulus);
 

diff --git a/src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp b/src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp
@@ -985,11 +985,8 @@ static void fill_continuation_entry(MacroAssembler* masm) {
 
   __ ldr(rscratch1, Address(rthread, JavaThread::cont_fastpath_offset()));
   __ str(rscratch1, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
-  __ ldr(rscratch1, Address(rthread, JavaThread::held_monitor_count_offset()));
-  __ str(rscratch1, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));
 
   __ str(zr, Address(rthread, JavaThread::cont_fastpath_offset()));
-  __ str(zr, Address(rthread, JavaThread::held_monitor_count_offset()));
 }
 
 // on entry, sp points to the ContinuationEntry
@@ -1005,50 +1002,6 @@ static void continuation_enter_cleanup(MacroAssembler* masm) {
 #endif
   __ ldr(rscratch1, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
   __ str(rscratch1, Address(rthread, JavaThread::cont_fastpath_offset()));
-
-  if (CheckJNICalls) {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ ldrw(rscratch1, Address(sp, ContinuationEntry::flags_offset()));
-    __ cbzw(rscratch1, L_skip_vthread_code);
-
-    // If the held monitor count is > 0 and this vthread is terminating then
-    // it failed to release a JNI monitor. So we issue the same log message
-    // that JavaThread::exit does.
-    __ ldr(rscratch1, Address(rthread, JavaThread::jni_monitor_count_offset()));
-    __ cbz(rscratch1, L_skip_vthread_code);
-
-    // Save return value potentially containing the exception oop in callee-saved R19.
-    __ mov(r19, r0);
-    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::log_jni_monitor_still_held));
-    // Restore potential return value.
-    __ mov(r0, r19);
-
-    // For vthreads we have to explicitly zero the JNI monitor count of the carrier
-    // on termination. The held count is implicitly zeroed below when we restore from
-    // the parent held count (which has to be zero).
-    __ str(zr, Address(rthread, JavaThread::jni_monitor_count_offset()));
-
-    __ bind(L_skip_vthread_code);
-  }
-#ifdef ASSERT
-  else {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ ldrw(rscratch1, Address(sp, ContinuationEntry::flags_offset()));
-    __ cbzw(rscratch1, L_skip_vthread_code);
-
-    // See comment just above. If not checking JNI calls the JNI count is only
-    // needed for assertion checking.
-    __ str(zr, Address(rthread, JavaThread::jni_monitor_count_offset()));
-
-    __ bind(L_skip_vthread_code);
-  }
-#endif
-
-  __ ldr(rscratch1, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));
-  __ str(rscratch1, Address(rthread, JavaThread::held_monitor_count_offset()));
-
   __ ldr(rscratch2, Address(sp, ContinuationEntry::parent_offset()));
   __ str(rscratch2, Address(rthread, JavaThread::cont_entry_offset()));
   __ add(rfp, sp, (int)ContinuationEntry::size());

diff --git a/src/hotspot/cpu/ppc/globalDefinitions_ppc.hpp b/src/hotspot/cpu/ppc/globalDefinitions_ppc.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2025, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2016 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -43,8 +43,6 @@ const bool CCallingConventionRequiresIntsAsLongs = true;
 
 #define SUPPORTS_NATIVE_CX8
 
-#define SUPPORT_MONITOR_COUNT
-
 // PPC64 is not specified as multi-copy-atomic
 // So we must not #define CPU_MULTI_COPY_ATOMIC
 

diff --git a/src/hotspot/cpu/ppc/sharedRuntime_ppc.cpp b/src/hotspot/cpu/ppc/sharedRuntime_ppc.cpp
@@ -1639,7 +1639,6 @@ static void fill_continuation_entry(MacroAssembler* masm, Register reg_cont_obj,
   assert_different_registers(reg_cont_obj, reg_flags);
   Register zero = R8_ARG6;
   Register tmp2 = R9_ARG7;
-  Register tmp3 = R10_ARG8;
 
   DEBUG_ONLY(__ block_comment("fill {"));
 #ifdef ASSERT
@@ -1655,12 +1654,9 @@ static void fill_continuation_entry(MacroAssembler* masm, Register reg_cont_obj,
   __ stw(zero, in_bytes(ContinuationEntry::pin_count_offset()), R1_SP);
 
   __ ld_ptr(tmp2, JavaThread::cont_fastpath_offset(), R16_thread);
-  __ ld(tmp3, in_bytes(JavaThread::held_monitor_count_offset()), R16_thread);
   __ st_ptr(tmp2, ContinuationEntry::parent_cont_fastpath_offset(), R1_SP);
-  __ std(tmp3, in_bytes(ContinuationEntry::parent_held_monitor_count_offset()), R1_SP);
 
   __ st_ptr(zero, JavaThread::cont_fastpath_offset(), R16_thread);
-  __ std(zero, in_bytes(JavaThread::held_monitor_count_offset()), R16_thread);
   DEBUG_ONLY(__ block_comment("} fill"));
 }
 
@@ -1681,7 +1677,6 @@ static void fill_continuation_entry(MacroAssembler* masm, Register reg_cont_obj,
 static void continuation_enter_cleanup(MacroAssembler* masm) {
   Register tmp1 = R8_ARG6;
   Register tmp2 = R9_ARG7;
-  Register tmp3 = R10_ARG8;
 
 #ifdef ASSERT
   __ block_comment("clean {");
@@ -1692,57 +1687,8 @@ static void continuation_enter_cleanup(MacroAssembler* masm) {
 
   __ ld_ptr(tmp1, ContinuationEntry::parent_cont_fastpath_offset(), R1_SP);
   __ st_ptr(tmp1, JavaThread::cont_fastpath_offset(), R16_thread);
-
-  if (CheckJNICalls) {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ lwz(R0, in_bytes(ContinuationEntry::flags_offset()), R1_SP);
-    __ cmpwi(CR0, R0, 0);
-    __ beq(CR0, L_skip_vthread_code);
-
-    // If the held monitor count is > 0 and this vthread is terminating then
-    // it failed to release a JNI monitor. So we issue the same log message
-    // that JavaThread::exit does.
-    __ ld(R0, in_bytes(JavaThread::jni_monitor_count_offset()), R16_thread);
-    __ cmpdi(CR0, R0, 0);
-    __ beq(CR0, L_skip_vthread_code);
-
-    // Save return value potentially containing the exception oop
-    Register ex_oop = R15_esp;   // nonvolatile register
-    __ mr(ex_oop, R3_RET);
-    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::log_jni_monitor_still_held));
-    // Restore potental return value
-    __ mr(R3_RET, ex_oop);
-
-    // For vthreads we have to explicitly zero the JNI monitor count of the carrier
-    // on termination. The held count is implicitly zeroed below when we restore from
-    // the parent held count (which has to be zero).
-    __ li(tmp1, 0);
-    __ std(tmp1, in_bytes(JavaThread::jni_monitor_count_offset()), R16_thread);
-
-    __ bind(L_skip_vthread_code);
-  }
-#ifdef ASSERT
-  else {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ lwz(R0, in_bytes(ContinuationEntry::flags_offset()), R1_SP);
-    __ cmpwi(CR0, R0, 0);
-    __ beq(CR0, L_skip_vthread_code);
-
-    // See comment just above. If not checking JNI calls the JNI count is only
-    // needed for assertion checking.
-    __ li(tmp1, 0);
-    __ std(tmp1, in_bytes(JavaThread::jni_monitor_count_offset()), R16_thread);
-
-    __ bind(L_skip_vthread_code);
-  }
-#endif
-
-  __ ld(tmp2, in_bytes(ContinuationEntry::parent_held_monitor_count_offset()), R1_SP);
-  __ ld_ptr(tmp3, ContinuationEntry::parent_offset(), R1_SP);
-  __ std(tmp2, in_bytes(JavaThread::held_monitor_count_offset()), R16_thread);
-  __ st_ptr(tmp3, JavaThread::cont_entry_offset(), R16_thread);
+  __ ld_ptr(tmp2, ContinuationEntry::parent_offset(), R1_SP);
+  __ st_ptr(tmp2, JavaThread::cont_entry_offset(), R16_thread);
   DEBUG_ONLY(__ block_comment("} clean"));
 }
 

diff --git a/src/hotspot/cpu/riscv/globalDefinitions_riscv.hpp b/src/hotspot/cpu/riscv/globalDefinitions_riscv.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2025, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2014, 2015, Red Hat Inc. All rights reserved.
  * Copyright (c) 2020, 2022, Huawei Technologies Co., Ltd. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
@@ -44,8 +44,6 @@ const bool CCallingConventionRequiresIntsAsLongs = false;
 
 #define SUPPORTS_NATIVE_CX8
 
-#define SUPPORT_MONITOR_COUNT
-
 #define SUPPORT_RESERVED_STACK_AREA
 
 #define USE_POINTERS_TO_REGISTER_IMPL_ARRAY

diff --git a/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp b/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp
@@ -225,36 +225,6 @@ void MacroAssembler::pop_cont_fastpath(Register java_thread) {
   bind(done);
 }
 
-void MacroAssembler::inc_held_monitor_count(Register tmp) {
-  Address dst(xthread, JavaThread::held_monitor_count_offset());
-  ld(tmp, dst);
-  addi(tmp, tmp, 1);
-  sd(tmp, dst);
-#ifdef ASSERT
-  Label ok;
-  test_bit(tmp, tmp, 63);
-  beqz(tmp, ok);
-  STOP("assert(held monitor count overflow)");
-  should_not_reach_here();
-  bind(ok);
-#endif
-}
-
-void MacroAssembler::dec_held_monitor_count(Register tmp) {
-  Address dst(xthread, JavaThread::held_monitor_count_offset());
-  ld(tmp, dst);
-  subi(tmp, tmp, 1);
-  sd(tmp, dst);
-#ifdef ASSERT
-  Label ok;
-  test_bit(tmp, tmp, 63);
-  beqz(tmp, ok);
-  STOP("assert(held monitor count underflow)");
-  should_not_reach_here();
-  bind(ok);
-#endif
-}
-
 int MacroAssembler::align(int modulus, int extra_offset) {
   CompressibleScope scope(this);
   intptr_t before = offset();

diff --git a/src/hotspot/cpu/riscv/macroAssembler_riscv.hpp b/src/hotspot/cpu/riscv/macroAssembler_riscv.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2014, 2020, Red Hat Inc. All rights reserved.
  * Copyright (c) 2020, 2024, Huawei Technologies Co., Ltd. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
@@ -849,9 +849,6 @@ class MacroAssembler: public Assembler {
   void push_cont_fastpath(Register java_thread = xthread);
   void pop_cont_fastpath(Register java_thread = xthread);
 
-  void inc_held_monitor_count(Register tmp);
-  void dec_held_monitor_count(Register tmp);
-
   // if heap base register is used - reinit it with the correct value
   void reinit_heapbase();
 

diff --git a/src/hotspot/cpu/riscv/sharedRuntime_riscv.cpp b/src/hotspot/cpu/riscv/sharedRuntime_riscv.cpp
@@ -885,11 +885,8 @@ static void fill_continuation_entry(MacroAssembler* masm) {
 
   __ ld(t0, Address(xthread, JavaThread::cont_fastpath_offset()));
   __ sd(t0, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
-  __ ld(t0, Address(xthread, JavaThread::held_monitor_count_offset()));
-  __ sd(t0, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));
 
   __ sd(zr, Address(xthread, JavaThread::cont_fastpath_offset()));
-  __ sd(zr, Address(xthread, JavaThread::held_monitor_count_offset()));
 }
 
 // on entry, sp points to the ContinuationEntry
@@ -905,50 +902,6 @@ static void continuation_enter_cleanup(MacroAssembler* masm) {
 
   __ ld(t0, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
   __ sd(t0, Address(xthread, JavaThread::cont_fastpath_offset()));
-
-  if (CheckJNICalls) {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ lwu(t0, Address(sp, ContinuationEntry::flags_offset()));
-    __ beqz(t0, L_skip_vthread_code);
-
-    // If the held monitor count is > 0 and this vthread is terminating then
-    // it failed to release a JNI monitor. So we issue the same log message
-    // that JavaThread::exit does.
-    __ ld(t0, Address(xthread, JavaThread::jni_monitor_count_offset()));
-    __ beqz(t0, L_skip_vthread_code);
-
-    // Save return value potentially containing the exception oop in callee-saved x9
-    __ mv(x9, x10);
-    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::log_jni_monitor_still_held));
-    // Restore potential return value
-    __ mv(x10, x9);
-
-    // For vthreads we have to explicitly zero the JNI monitor count of the carrier
-    // on termination. The held count is implicitly zeroed below when we restore from
-    // the parent held count (which has to be zero).
-    __ sd(zr, Address(xthread, JavaThread::jni_monitor_count_offset()));
-
-    __ bind(L_skip_vthread_code);
-  }
-#ifdef ASSERT
-  else {
-    // Check if this is a virtual thread continuation
-    Label L_skip_vthread_code;
-    __ lwu(t0, Address(sp, ContinuationEntry::flags_offset()));
-    __ beqz(t0, L_skip_vthread_code);
-
-    // See comment just above. If not checking JNI calls the JNI count is only
-    // needed for assertion checking.
-    __ sd(zr, Address(xthread, JavaThread::jni_monitor_count_offset()));
-
-    __ bind(L_skip_vthread_code);
-  }
-#endif
-
-  __ ld(t0, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));
-  __ sd(t0, Address(xthread, JavaThread::held_monitor_count_offset()));
-
   __ ld(t0, Address(sp, ContinuationEntry::parent_offset()));
   __ sd(t0, Address(xthread, JavaThread::cont_entry_offset()));
   __ add(fp, sp, (int)ContinuationEntry::size() + 2 * wordSize /* 2 extra words to match up with leave() */);

diff --git a/src/hotspot/cpu/x86/globalDefinitions_x86.hpp b/src/hotspot/cpu/x86/globalDefinitions_x86.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,8 +34,6 @@ const bool CCallingConventionRequiresIntsAsLongs = false;
 
 #define SUPPORTS_NATIVE_CX8
 
-#define SUPPORT_MONITOR_COUNT
-
 #define CPU_MULTI_COPY_ATOMIC
 
 // The expected size in bytes of a cache line.

diff --git a/src/hotspot/cpu/x86/macroAssembler_x86.cpp b/src/hotspot/cpu/x86/macroAssembler_x86.cpp
@@ -2431,14 +2431,6 @@ void MacroAssembler::pop_cont_fastpath() {
   bind(L_done);
 }
 
-void MacroAssembler::inc_held_monitor_count() {
-  incrementq(Address(r15_thread, JavaThread::held_monitor_count_offset()));
-}
-
-void MacroAssembler::dec_held_monitor_count() {
-  decrementq(Address(r15_thread, JavaThread::held_monitor_count_offset()));
-}
-
 #ifdef ASSERT
 void MacroAssembler::stop_if_in_cont(Register cont, const char* name) {
   Label no_cont;

diff --git a/src/hotspot/cpu/x86/macroAssembler_x86.hpp b/src/hotspot/cpu/x86/macroAssembler_x86.hpp
@@ -472,9 +472,6 @@ class MacroAssembler: public Assembler {
   void push_cont_fastpath();
   void pop_cont_fastpath();
 
-  void inc_held_monitor_count();
-  void dec_held_monitor_count();
-
   DEBUG_ONLY(void stop_if_in_cont(Register cont_reg, const char* name);)
 
   // Round up to a power of two