src/hotspot/cpu/x86/c2_CodeStubs_x86.cpp

*** 94,10 ***
--- 94,11 ---
    }
  
    { // Restore held monitor count and slow path.
  
      __ bind(restore_held_monitor_count_and_slow_path);
+     __ bind(_slow_path);
      // Restore held monitor count.
      __ increment(Address(_thread, JavaThread::held_monitor_count_offset()));
      // increment will always result in ZF = 0 (no overflows).
      __ jmp(slow_path_continuation());
    }

*** 110,32 ***
      const Register monitor = _mark;
  
  #ifndef _LP64
      __ jmpb(restore_held_monitor_count_and_slow_path);
  #else // _LP64
      // successor null check.
!     __ cmpptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(succ)), NULL_WORD);
      __ jccb(Assembler::equal, restore_held_monitor_count_and_slow_path);
  
      // Release lock.
!     __ movptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)), NULL_WORD);
  
      // Fence.
      // Instead of MFENCE we use a dummy locked add of 0 to the top-of-stack.
      __ lock(); __ addl(Address(rsp, 0), 0);
  
      // Recheck successor.
!     __ cmpptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(succ)), NULL_WORD);
      // Observed a successor after the release -> fence we have handed off the monitor
      __ jccb(Assembler::notEqual, fix_zf_and_unlocked);
  
      // Try to relock, if it fails the monitor has been handed over
      // TODO: Caveat, this may fail due to deflation, which does
      //       not handle the monitor handoff. Currently only works
      //       due to the responsible thread.
      __ xorptr(rax, rax);
!     __ lock(); __ cmpxchgptr(_thread, Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)));
      __ jccb  (Assembler::equal, restore_held_monitor_count_and_slow_path);
  #endif
  
      __ bind(fix_zf_and_unlocked);
      __ xorl(rax, rax);
--- 111,36 ---
      const Register monitor = _mark;
  
  #ifndef _LP64
      __ jmpb(restore_held_monitor_count_and_slow_path);
  #else // _LP64
+     const ByteSize monitor_tag = in_ByteSize(UseObjectMonitorTable ? 0 : checked_cast<int>(markWord::monitor_value));
+     const Address succ_address{monitor, ObjectMonitor::succ_offset() - monitor_tag};
+     const Address owner_address{monitor, ObjectMonitor::owner_offset() - monitor_tag};
+ 
      // successor null check.
!     __ cmpptr(succ_address, NULL_WORD);
      __ jccb(Assembler::equal, restore_held_monitor_count_and_slow_path);
  
      // Release lock.
!     __ movptr(owner_address, NULL_WORD);
  
      // Fence.
      // Instead of MFENCE we use a dummy locked add of 0 to the top-of-stack.
      __ lock(); __ addl(Address(rsp, 0), 0);
  
      // Recheck successor.
!     __ cmpptr(succ_address, NULL_WORD);
      // Observed a successor after the release -> fence we have handed off the monitor
      __ jccb(Assembler::notEqual, fix_zf_and_unlocked);
  
      // Try to relock, if it fails the monitor has been handed over
      // TODO: Caveat, this may fail due to deflation, which does
      //       not handle the monitor handoff. Currently only works
      //       due to the responsible thread.
      __ xorptr(rax, rax);
!     __ lock(); __ cmpxchgptr(_thread, owner_address);
      __ jccb  (Assembler::equal, restore_held_monitor_count_and_slow_path);
  #endif
  
      __ bind(fix_zf_and_unlocked);
      __ xorl(rax, rax);