# HG changeset patch
# User dholmes
# Date 1565821583 14400
# Node ID 7284b00e6db363fa8fa473eadd82f4c3904e0668
# Parent  ececb6dae777e622abda42c705fd984a42f46b5a
8228858: Reimplement JVM_RawMonitors to use PlatformMutex
Reviewed-by: coleenp, dcubed, pchilanomate

diff -r ececb6dae777 -r 7284b00e6db3 src/hotspot/share/prims/jvm.cpp
--- a/src/hotspot/share/prims/jvm.cpp	Wed Aug 14 20:32:44 2019 +0200
+++ b/src/hotspot/share/prims/jvm.cpp	Wed Aug 14 18:26:23 2019 -0400
@@ -3384,32 +3384,33 @@
 JVM_END
 
 
-// Raw monitor support //////////////////////////////////////////////////////////////////////
-
-// The lock routine below calls lock_without_safepoint_check in order to get a raw lock
-// without interfering with the safepoint mechanism. The routines are not JVM_LEAF because
-// they might be called by non-java threads. The JVM_LEAF installs a NoHandleMark check
-// that only works with java threads.
+// VM Raw monitor support //////////////////////////////////////////////////////////////////////
+
+// VM Raw monitors (not to be confused with JvmtiRawMonitors) are a simple mutual exclusion
+// lock (not actually monitors: no wait/notify) that is exported by the VM for use by JDK
+// library code. They may be used by JavaThreads and non-JavaThreads and do not participate
+// in the safepoint protocol, thread suspension, thread interruption, or anything of that
+// nature. JavaThreads will be "in native" when using this API from JDK code.
 
 
 JNIEXPORT void* JNICALL JVM_RawMonitorCreate(void) {
   VM_Exit::block_if_vm_exited();
   JVMWrapper("JVM_RawMonitorCreate");
-  return new Mutex(Mutex::native, "JVM_RawMonitorCreate");
+  return new os::PlatformMutex();
 }
 
 
 JNIEXPORT void JNICALL  JVM_RawMonitorDestroy(void *mon) {
   VM_Exit::block_if_vm_exited();
   JVMWrapper("JVM_RawMonitorDestroy");
-  delete ((Mutex*) mon);
+  delete ((os::PlatformMutex*) mon);
 }
 
 
 JNIEXPORT jint JNICALL JVM_RawMonitorEnter(void *mon) {
   VM_Exit::block_if_vm_exited();
   JVMWrapper("JVM_RawMonitorEnter");
-  ((Mutex*) mon)->jvm_raw_lock();
+  ((os::PlatformMutex*) mon)->lock();
   return 0;
 }
 
@@ -3417,7 +3418,7 @@
 JNIEXPORT void JNICALL JVM_RawMonitorExit(void *mon) {
   VM_Exit::block_if_vm_exited();
   JVMWrapper("JVM_RawMonitorExit");
-  ((Mutex*) mon)->jvm_raw_unlock();
+  ((os::PlatformMutex*) mon)->unlock();
 }
 
 
diff -r ececb6dae777 -r 7284b00e6db3 src/hotspot/share/runtime/mutex.cpp
--- a/src/hotspot/share/runtime/mutex.cpp	Wed Aug 14 20:32:44 2019 +0200
+++ b/src/hotspot/share/runtime/mutex.cpp	Wed Aug 14 18:26:23 2019 -0400
@@ -232,24 +232,6 @@
   return wait_status != 0;          // return true IFF timeout
 }
 
-
-// Temporary JVM_RawMonitor* support.
-// Yet another degenerate version of Monitor::lock() or lock_without_safepoint_check()
-// jvm_raw_lock() and _unlock() can be called by non-Java threads via JVM_RawMonitorEnter.
-// There's no expectation that JVM_RawMonitors will interoperate properly with the native
-// Mutex-Monitor constructs.  We happen to implement JVM_RawMonitors in terms of
-// native Mutex-Monitors simply as a matter of convenience.
-
-void Monitor::jvm_raw_lock() {
-  _lock.lock();
-  assert_owner(NULL);
-}
-
-void Monitor::jvm_raw_unlock() {
-  assert_owner(NULL);
-  _lock.unlock();
-}
-
 Monitor::~Monitor() {
   assert_owner(NULL);
 }
diff -r ececb6dae777 -r 7284b00e6db3 src/hotspot/share/runtime/mutex.hpp
--- a/src/hotspot/share/runtime/mutex.hpp	Wed Aug 14 20:32:44 2019 +0200
+++ b/src/hotspot/share/runtime/mutex.hpp	Wed Aug 14 18:26:23 2019 -0400
@@ -52,8 +52,10 @@
   // inherently a bit more special than even locks of the 'special' rank.
   // NOTE: It is critical that the rank 'special' be the lowest (earliest)
   // (except for "event" and "access") for the deadlock detection to work correctly.
-  // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate,
-  // which being external to the VM are not subject to deadlock detection.
+  // The rank native was only for use in Mutexes created by JVM_RawMonitorCreate,
+  // which being external to the VM are not subject to deadlock detection,
+  // however it has now been used by other locks that don't fit into the
+  // deadlock detection scheme.
   // While at a safepoint no mutexes of rank safepoint are held by any thread.
   // The rank named "leaf" is probably historical (and should
   // be changed) -- mutexes of this rank aren't really leaf mutexes
@@ -174,10 +176,6 @@
   Thread* owner() const         { return _owner; }
   bool owned_by_self() const;
 
-  // Support for JVM_RawMonitorEnter & JVM_RawMonitorExit. These can be called by
-  // non-Java thread. (We should really have a RawMonitor abstraction)
-  void jvm_raw_lock();
-  void jvm_raw_unlock();
   const char *name() const                  { return _name; }
 
   void print_on_error(outputStream* st) const;
diff -r ececb6dae777 -r 7284b00e6db3 src/hotspot/share/runtime/park.cpp
--- a/src/hotspot/share/runtime/park.cpp	Wed Aug 14 20:32:44 2019 +0200
+++ b/src/hotspot/share/runtime/park.cpp	Wed Aug 14 18:26:23 2019 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, 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
@@ -53,7 +53,6 @@
 ParkEvent * volatile ParkEvent::FreeList = NULL ;
 
 ParkEvent * ParkEvent::Allocate (Thread * t) {
-  // In rare cases -- JVM_RawMonitor* operations -- we can find t == null.
   ParkEvent * ev ;
 
   // Start by trying to recycle an existing but unassociated
@@ -164,4 +163,3 @@
   }
   Thread::SpinRelease(&ListLock);
 }
-