diff --git a/src/hotspot/cpu/s390/c1_MacroAssembler_s390.cpp b/src/hotspot/cpu/s390/c1_MacroAssembler_s390.cpp
index 91f8fe16be8..85238a51009 100644
--- a/src/hotspot/cpu/s390/c1_MacroAssembler_s390.cpp
+++ b/src/hotspot/cpu/s390/c1_MacroAssembler_s390.cpp
@@ -86,7 +86,6 @@ void C1_MacroAssembler::verified_entry(bool breakAtEntry) {
 void C1_MacroAssembler::lock_object(Register hdr, Register obj, Register disp_hdr, Label& slow_case) {
   const int hdr_offset = oopDesc::mark_offset_in_bytes();
   assert_different_registers(hdr, obj, disp_hdr);
-  NearLabel done;
 
   verify_oop(obj, FILE_AND_LINE);
 
@@ -102,40 +101,47 @@ void C1_MacroAssembler::lock_object(Register hdr, Register obj, Register disp_hd
     z_btrue(slow_case);
   }
 
-  // and mark it as unlocked.
-  z_oill(hdr, markWord::unlocked_value);
-  // Save unlocked object header into the displaced header location on the stack.
-  z_stg(hdr, Address(disp_hdr, (intptr_t)0));
-  // Test if object header is still the same (i.e. unlocked), and if so, store the
-  // displaced header address in the object header. If it is not the same, get the
-  // object header instead.
-  z_csg(hdr, disp_hdr, hdr_offset, obj);
-  // If the object header was the same, we're done.
-  branch_optimized(Assembler::bcondEqual, done);
-  // If the object header was not the same, it is now in the hdr register.
-  // => Test if it is a stack pointer into the same stack (recursive locking), i.e.:
-  //
-  // 1) (hdr & markWord::lock_mask_in_place) == 0
-  // 2) rsp <= hdr
-  // 3) hdr <= rsp + page_size
-  //
-  // These 3 tests can be done by evaluating the following expression:
-  //
-  // (hdr - Z_SP) & (~(page_size-1) | markWord::lock_mask_in_place)
-  //
-  // assuming both the stack pointer and page_size have their least
-  // significant 2 bits cleared and page_size is a power of 2
-  z_sgr(hdr, Z_SP);
+  assert(LockingMode != LM_MONITOR, "LM_MONITOR is already handled, by emit_lock()");
 
-  load_const_optimized(Z_R0_scratch, (~(os::vm_page_size()-1) | markWord::lock_mask_in_place));
-  z_ngr(hdr, Z_R0_scratch); // AND sets CC (result eq/ne 0).
-  // For recursive locking, the result is zero. => Save it in the displaced header
-  // location (null in the displaced hdr location indicates recursive locking).
-  z_stg(hdr, Address(disp_hdr, (intptr_t)0));
-  // Otherwise we don't care about the result and handle locking via runtime call.
-  branch_optimized(Assembler::bcondNotZero, slow_case);
-  // done
-  bind(done);
+  if (LockingMode == LM_LIGHTWEIGHT) {
+    Unimplemented();
+  } else if (LockingMode == LM_LEGACY) {
+    NearLabel done;
+    // and mark it as unlocked.
+    z_oill(hdr, markWord::unlocked_value);
+    // Save unlocked object header into the displaced header location on the stack.
+    z_stg(hdr, Address(disp_hdr, (intptr_t) 0));
+    // Test if object header is still the same (i.e. unlocked), and if so, store the
+    // displaced header address in the object header. If it is not the same, get the
+    // object header instead.
+    z_csg(hdr, disp_hdr, hdr_offset, obj);
+    // If the object header was the same, we're done.
+    branch_optimized(Assembler::bcondEqual, done);
+    // If the object header was not the same, it is now in the hdr register.
+    // => Test if it is a stack pointer into the same stack (recursive locking), i.e.:
+    //
+    // 1) (hdr & markWord::lock_mask_in_place) == 0
+    // 2) rsp <= hdr
+    // 3) hdr <= rsp + page_size
+    //
+    // These 3 tests can be done by evaluating the following expression:
+    //
+    // (hdr - Z_SP) & (~(page_size-1) | markWord::lock_mask_in_place)
+    //
+    // assuming both the stack pointer and page_size have their least
+    // significant 2 bits cleared and page_size is a power of 2
+    z_sgr(hdr, Z_SP);
+
+    load_const_optimized(Z_R0_scratch, (~(os::vm_page_size() - 1) | markWord::lock_mask_in_place));
+    z_ngr(hdr, Z_R0_scratch); // AND sets CC (result eq/ne 0).
+    // For recursive locking, the result is zero. => Save it in the displaced header
+    // location (null in the displaced hdr location indicates recursive locking).
+    z_stg(hdr, Address(disp_hdr, (intptr_t) 0));
+    // Otherwise we don't care about the result and handle locking via runtime call.
+    branch_optimized(Assembler::bcondNotZero, slow_case);
+    // done
+    bind(done);
+  }
 }
 
 void C1_MacroAssembler::unlock_object(Register hdr, Register obj, Register disp_hdr, Label& slow_case) {
@@ -144,21 +150,29 @@ void C1_MacroAssembler::unlock_object(Register hdr, Register obj, Register disp_
   assert_different_registers(hdr, obj, disp_hdr);
   NearLabel done;
 
-  // Load displaced header.
-  z_ltg(hdr, Address(disp_hdr, (intptr_t)0));
-  // If the loaded hdr is null we had recursive locking, and we are done.
-  z_bre(done);
+  if (LockingMode != LM_LIGHTWEIGHT) {
+    // Load displaced header.
+    z_ltg(hdr, Address(disp_hdr, (intptr_t) 0));
+    // If the loaded hdr is null we had recursive locking, and we are done.
+    z_bre(done);
+  }
+
   // Load object.
   z_lg(obj, Address(disp_hdr, BasicObjectLock::obj_offset_in_bytes()));
   verify_oop(obj, FILE_AND_LINE);
-  // Test if object header is pointing to the displaced header, and if so, restore
-  // the displaced header in the object. If the object header is not pointing to
-  // the displaced header, get the object header instead.
-  z_csg(disp_hdr, hdr, hdr_offset, obj);
-  // If the object header was not pointing to the displaced header,
-  // we do unlocking via runtime call.
-  branch_optimized(Assembler::bcondNotEqual, slow_case);
-  // done
+
+  if (LockingMode == LM_LIGHTWEIGHT) {
+    Unimplemented();
+  } else {
+    // Test if object header is pointing to the displaced header, and if so, restore
+    // the displaced header in the object. If the object header is not pointing to
+    // the displaced header, get the object header instead.
+    z_csg(disp_hdr, hdr, hdr_offset, obj);
+    // If the object header was not pointing to the displaced header,
+    // we do unlocking via runtime call.
+    branch_optimized(Assembler::bcondNotEqual, slow_case);
+    // done
+  }
   bind(done);
 }
 
diff --git a/src/hotspot/cpu/s390/macroAssembler_s390.cpp b/src/hotspot/cpu/s390/macroAssembler_s390.cpp
index ebd678fea08..8ca27efa71d 100644
--- a/src/hotspot/cpu/s390/macroAssembler_s390.cpp
+++ b/src/hotspot/cpu/s390/macroAssembler_s390.cpp
@@ -3171,22 +3171,28 @@ void MacroAssembler::compiler_fast_lock_object(Register oop, Register box, Regis
   z_nill(temp, markWord::monitor_value);
   z_brne(object_has_monitor);
 
-  // Set mark to markWord | markWord::unlocked_value.
-  z_oill(displacedHeader, markWord::unlocked_value);
+  if (LockingMode != LM_MONITOR) {
+    // Set mark to markWord | markWord::unlocked_value.
+    z_oill(displacedHeader, markWord::unlocked_value);
 
-  // Load Compare Value application register.
+    // Load Compare Value application register.
 
-  // Initialize the box (must happen before we update the object mark).
-  z_stg(displacedHeader, BasicLock::displaced_header_offset_in_bytes(), box);
+    // Initialize the box (must happen before we update the object mark).
+    z_stg(displacedHeader, BasicLock::displaced_header_offset_in_bytes(), box);
 
-  // Memory Fence (in cmpxchgd)
-  // Compare object markWord with mark and if equal exchange scratch1 with object markWord.
+    // Memory Fence (in cmpxchgd)
+    // Compare object markWord with mark and if equal exchange scratch1 with object markWord.
 
-  // If the compare-and-swap succeeded, then we found an unlocked object and we
-  // have now locked it.
-  z_csg(displacedHeader, box, 0, oop);
-  assert(currentHeader==displacedHeader, "must be same register"); // Identified two registers from z/Architecture.
-  z_bre(done);
+    // If the compare-and-swap succeeded, then we found an unlocked object and we
+    // have now locked it.
+    z_csg(displacedHeader, box, 0, oop);
+    assert(currentHeader == displacedHeader, "must be same register"); // Identified two registers from z/Architecture.
+    z_bre(done);
+  } else {
+    // Set NE to indicate 'failure' -> take slow-path
+    z_ltgr(oop, oop);
+    z_bru(done);
+  }
 
   // We did not see an unlocked object so try the fast recursive case.
 
@@ -3238,10 +3244,12 @@ void MacroAssembler::compiler_fast_unlock_object(Register oop, Register box, Reg
 
   BLOCK_COMMENT("compiler_fast_unlock_object {");
 
-  // Find the lock address and load the displaced header from the stack.
-  // if the displaced header is zero, we have a recursive unlock.
-  load_and_test_long(displacedHeader, Address(box, BasicLock::displaced_header_offset_in_bytes()));
-  z_bre(done);
+  if (LockingMode != LM_MONITOR) {
+    // Find the lock address and load the displaced header from the stack.
+    // if the displaced header is zero, we have a recursive unlock.
+    load_and_test_long(displacedHeader, Address(box, BasicLock::displaced_header_offset_in_bytes()));
+    z_bre(done);
+  }
 
   // Handle existing monitor.
   // The object has an existing monitor iff (mark & monitor_value) != 0.
@@ -3250,12 +3258,18 @@ void MacroAssembler::compiler_fast_unlock_object(Register oop, Register box, Reg
   z_nill(currentHeader, markWord::monitor_value);
   z_brne(object_has_monitor);
 
-  // Check if it is still a light weight lock, this is true if we see
-  // the stack address of the basicLock in the markWord of the object
-  // copy box to currentHeader such that csg does not kill it.
-  z_lgr(currentHeader, box);
-  z_csg(currentHeader, displacedHeader, 0, oop);
-  z_bru(done); // Csg sets CR as desired.
+  if (LockingMode != LM_MONITOR) {
+    // Check if it is still a light weight lock, this is true if we see
+    // the stack address of the basicLock in the markWord of the object
+    // copy box to currentHeader such that csg does not kill it.
+    z_lgr(currentHeader, box);
+    z_csg(currentHeader, displacedHeader, 0, oop);
+    z_bru(done); // Csg sets CR as desired.
+  } else {
+    // Set NE to indicate 'failure' -> take slow-path
+    z_ltgr(oop, oop);
+    z_bru(done);
+  }
 
   // Handle existing monitor.
   bind(object_has_monitor);
diff --git a/src/hotspot/share/runtime/arguments.cpp b/src/hotspot/share/runtime/arguments.cpp
index f9b324bead3..d83a54b0023 100644
--- a/src/hotspot/share/runtime/arguments.cpp
+++ b/src/hotspot/share/runtime/arguments.cpp
@@ -1921,7 +1921,7 @@ bool Arguments::check_vm_args_consistency() {
     FLAG_SET_CMDLINE(LockingMode, LM_MONITOR);
   }
 
-#if !defined(X86) && !defined(AARCH64) && !defined(PPC64) && !defined(RISCV64)
+#if !defined(X86) && !defined(AARCH64) && !defined(PPC64) && !defined(RISCV64) && !defined(S390)
   if (LockingMode == LM_MONITOR) {
     jio_fprintf(defaultStream::error_stream(),
                 "LockingMode == 0 (LM_MONITOR) is not fully implemented on this architecture");
diff --git a/src/hotspot/share/runtime/synchronizer.cpp b/src/hotspot/share/runtime/synchronizer.cpp
index 3479bde358d..69a712bfb76 100644
--- a/src/hotspot/share/runtime/synchronizer.cpp
+++ b/src/hotspot/share/runtime/synchronizer.cpp
@@ -486,7 +486,7 @@ void ObjectSynchronizer::handle_sync_on_value_based_class(Handle obj, JavaThread
 }
 
 static bool useHeavyMonitors() {
-#if defined(X86) || defined(AARCH64) || defined(PPC64) || defined(RISCV64)
+#if defined(X86) || defined(AARCH64) || defined(PPC64) || defined(RISCV64) || defined(S390)
   return LockingMode == LM_MONITOR;
 #else
   return false;
diff --git a/test/jdk/java/util/concurrent/ConcurrentHashMap/MapLoops.java b/test/jdk/java/util/concurrent/ConcurrentHashMap/MapLoops.java
index b4e96b9f794..eacfaeb0785 100644
--- a/test/jdk/java/util/concurrent/ConcurrentHashMap/MapLoops.java
+++ b/test/jdk/java/util/concurrent/ConcurrentHashMap/MapLoops.java
@@ -48,7 +48,7 @@
 /*
  * @test
  * @summary Exercise multithreaded maps, using only heavy monitors.
- * @requires os.arch=="x86" | os.arch=="i386" | os.arch=="amd64" | os.arch=="x86_64" | os.arch=="aarch64" | os.arch == "ppc64" | os.arch == "ppc64le" | os.arch == "riscv64"
+ * @requires os.arch=="x86" | os.arch=="i386" | os.arch=="amd64" | os.arch=="x86_64" | os.arch=="aarch64" | os.arch == "ppc64" | os.arch == "ppc64le" | os.arch == "riscv64" | os.arch == "s390x"
  * @requires vm.debug
  * @library /test/lib
  * @run main/othervm/timeout=1600 -XX:+UseHeavyMonitors -XX:+VerifyHeavyMonitors MapLoops