src/hotspot/cpu/x86/macroAssembler_x86.cpp

rev 55494 : imported patch dcubed.monitor_deflate_conc.v2.05

*** 1837,1848 ****
    lock();
    cmpxchgptr(r15_thread, Address(scrReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)));
    // Unconditionally set box->_displaced_header = markOopDesc::unused_mark().
    // Without cast to int32_t movptr will destroy r10 which is typically obj.
    movptr(Address(boxReg, 0), (int32_t)intptr_t(markOopDesc::unused_mark()));
    // Intentional fall-through into DONE_LABEL ...
!   // Propagate ICC.ZF from CAS above into DONE_LABEL.
  #endif // _LP64
  #if INCLUDE_RTM_OPT
    } // use_rtm()
  #endif
    // DONE_LABEL is a hot target - we'd really like to place it at the
--- 1837,1868 ----
    lock();
    cmpxchgptr(r15_thread, Address(scrReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)));
    // Unconditionally set box->_displaced_header = markOopDesc::unused_mark().
    // Without cast to int32_t movptr will destroy r10 which is typically obj.
    movptr(Address(boxReg, 0), (int32_t)intptr_t(markOopDesc::unused_mark()));
+   // The following code to verify that the object field still refers
+   // to the object we are trying to lock is not needed with safepoint
+   // based deflation. It is also not needed with async deflation when
+   // the DEFLATER_MARKER is allowed to linger in the owner field in an
+   // async deflated ObjectMonitor until replaced by the next owner value.
+   // We keep this code as a sanity check against bugs in other parts
+   // of the async deflation mechanism.
+   //
+   // If we weren't able to swing _owner from NULL to r15_thread
+   // then take the slow path.
+   jccb(Assembler::notZero, DONE_LABEL);
+   // r15_thread is now the owner so verify that the ObjectMonitor
+   // still refers to the same object.
+   cmpptr(objReg, Address(scrReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(object)));
+   // The ObjectMonitor still refers to the same object so
+   // r15_thread's ownership is valid.
+   jccb(Assembler::zero, DONE_LABEL);
+   // The ObjectMonitor does not refer to the same object so
+   // drop ownership.
+   movptr(Address(scrReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)), NULL_WORD);
    // Intentional fall-through into DONE_LABEL ...
!   // Propagate ICC.ZF from cmpptr() above into DONE_LABEL.
  #endif // _LP64
  #if INCLUDE_RTM_OPT
    } // use_rtm()
  #endif
    // DONE_LABEL is a hot target - we'd really like to place it at the