Index: jvmti.cc
===================================================================
--- jvmti.cc	(revision 121442)
+++ jvmti.cc	(working copy)
@@ -27,7 +27,6 @@
 
 #include <java/lang/Class.h>
 #include <java/lang/ClassLoader.h>
-#include <java/lang/Object.h>
 #include <java/lang/OutOfMemoryError.h>
 #include <java/lang/Thread.h>
 #include <java/lang/ThreadGroup.h>
@@ -37,6 +36,8 @@
 #include <java/lang/reflect/Modifier.h>
 #include <java/util/Collection.h>
 #include <java/util/HashMap.h>
+#include <java/util/concurrent/locks/Lock.h>
+#include <java/util/concurrent/locks/ReentrantReadWriteLock.h>
 #include <java/net/URL.h>
 
 static void check_enabled_events (void);
@@ -103,7 +104,8 @@
   struct jvmti_env_list *next;
 };
 static struct jvmti_env_list *_jvmtiEnvironments = NULL;
-static java::lang::Object *_envListLock = NULL;
+static java::util::concurrent::locks::
+ReentrantReadWriteLock *_envListLock = NULL;
 #define FOREACH_ENVIRONMENT(Ele) \
   for (Ele = _jvmtiEnvironments; Ele != NULL; Ele = Ele->next)
 
@@ -896,7 +898,7 @@
     return JVMTI_ERROR_INVALID_ENVIRONMENT;
   else
     {
-      JvSynchronize dummy (_envListLock);
+      _envListLock->writeLock ()->lock ();
       if (_jvmtiEnvironments->env == env)
 	{
 	  struct jvmti_env_list *next = _jvmtiEnvironments->next;
@@ -909,12 +911,16 @@
 	  while (e->next != NULL && e->next->env != env)
 	    e = e->next;
 	  if (e->next == NULL)
-	    return JVMTI_ERROR_INVALID_ENVIRONMENT;
+	    {
+	      _envListLock->writeLock ()->unlock ();
+	      return JVMTI_ERROR_INVALID_ENVIRONMENT;
+	    }
 
 	  struct jvmti_env_list *next = e->next->next;
 	  _Jv_Free (e->next);
 	  e->next = next;
 	}
+      _envListLock->writeLock ()->unlock ();
     }
 
   _Jv_Free (env);
@@ -1215,18 +1221,24 @@
 
   int index = EVENT_INDEX (type); // safe since caller checks this
 
-  JvSynchronize dummy (_envListLock);
-  struct jvmti_env_list *e;
-  FOREACH_ENVIRONMENT (e)
+  if (_jvmtiEnvironments != NULL)
     {
-      char *addr
-	= reinterpret_cast<char *> (&e->env->callbacks) + offset;
-      void **callback = reinterpret_cast<void **> (addr);
-      if (e->env->enabled[index] && *callback != NULL)
+      _envListLock->readLock ()->lock ();
+      struct jvmti_env_list *e;
+      FOREACH_ENVIRONMENT (e)
 	{
-	  *enabled = true;
-	  return;
+	  char *addr
+	    = reinterpret_cast<char *> (&e->env->callbacks) + offset;
+	  void **callback = reinterpret_cast<void **> (addr);
+	  if (e->env->enabled[index] && *callback != NULL)
+	    {
+	      *enabled = true;
+	      _envListLock->readLock ()->unlock ();
+	      return;
+	    }
 	}
+
+      _envListLock->readLock ()->unlock ();
     }
 
   *enabled = false;
@@ -1739,25 +1751,23 @@
   _Jv_JVMTIEnv *env
     = (_Jv_JVMTIEnv *) _Jv_MallocUnchecked (sizeof (_Jv_JVMTIEnv));
   env->p = &_Jv_JVMTI_Interface;
+  struct jvmti_env_list *element
+    = (struct jvmti_env_list *) _Jv_MallocUnchecked (sizeof (struct jvmti_env_list));
+  element->env = env;
+  element->next = NULL;
 
-  {
-    JvSynchronize dummy (_envListLock);
-    struct jvmti_env_list *element
-      = (struct jvmti_env_list *) _Jv_MallocUnchecked (sizeof (struct jvmti_env_list));
-    element->env = env;
-    element->next = NULL;
+  _envListLock->writeLock ()->lock ();
+  if (_jvmtiEnvironments == NULL)
+    _jvmtiEnvironments = element;
+  else
+    {
+      struct jvmti_env_list *e;
+      for (e = _jvmtiEnvironments; e->next != NULL; e = e->next)
+	;
+      e->next = element;
+    }
+  _envListLock->writeLock ()->unlock ();
 
-    if (_jvmtiEnvironments == NULL)
-      _jvmtiEnvironments = element;
-    else
-      {
-	struct jvmti_env_list *e;
-	for (e = _jvmtiEnvironments; e->next != NULL; e = e->next)
-	  ;
-	e->next = element;
-      }
-  }
-
   /* Mark JVMTI active. This is used to force the interpreter
      to use either debugging or non-debugging code. Once JVMTI
      has been enabled, the non-debug interpreter cannot be used. */
@@ -1769,7 +1779,8 @@
 _Jv_JVMTI_Init ()
 {
   _jvmtiEnvironments = NULL;
-  _envListLock = new java::lang::Object ();
+  _envListLock
+    = new java::util::concurrent::locks::ReentrantReadWriteLock ();
 
   // No environments, so this should set all JVMTI:: members to false
   check_enabled_events ();
@@ -2133,7 +2144,7 @@
   va_list args;
   va_start (args, event_thread);
 
-  JvSynchronize dummy (_envListLock);
+  _envListLock->readLock ()->lock ();
   struct jvmti_env_list *e;
   FOREACH_ENVIRONMENT (e)
     {
@@ -2149,6 +2160,6 @@
 	  post_event (e->env, type, event_thread, args);
 	}
     }
-
+  _envListLock->readLock ()->unlock ();
   va_end (args);
 }