Patch: Implement java.lang.Thread.holdsLock

jlquinn@optonline.net jlquinn@optonline.net
Fri Oct 17 01:57:00 GMT 2003


I was looking at the API comparison and saw that this is the only function
missing from java/lang.  What do you think?

Thanks,
Jerry


2003-10-16  Jerry Quinn  <jlquinn@optonline.net>

        * posix-threads.cc (_Jv_CondNotify,_Jv_CondNotifyAll): Rename
        _Jv_PthreadCheckMonitor to _Jv_MutexCheckMonitor.
	* include/no-threads.h (_Jv_MutexCheckMonitor): New.
	* include/posix-threads.h (_Jv_MutexCheckMonitor): Rename from
        _Jv_PthreadCheckMonitor.  Simplify code.
	(_Jv_MutexUnlock): Use _Jv_MutexCheckMonitor.
	* include/win32-threads.h (_Jv_MutexCheckMonitor): New.
	* java/lang/Object.h (_Jv_ObjectCheckMonitor): Declare.
	* java/lang/Thread.java (holdsLock): New.
	* java/lang/natObject.cc (_Jv_ObjectCheckMonitor): New, with and
        without JV_HASH_SYNCHRONIZATION.
	* java/lang/natThread.cc (java::lang::Thread::holdsLock): New.


Index: posix-threads.cc
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/posix-threads.cc,v
retrieving revision 1.33
diff -u -w -r1.33 posix-threads.cc
--- posix-threads.cc	2 Mar 2003 01:24:40 -0000	1.33
+++ posix-threads.cc	17 Oct 2003 01:44:29 -0000
@@ -193,7 +193,7 @@
 int
 _Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 {
-  if (_Jv_PthreadCheckMonitor (mu))
+  if (_Jv_MutexCheckMonitor (mu))
     return _JV_NOT_OWNER;
 
   _Jv_Thread_t *target;
@@ -232,7 +232,7 @@
 int
 _Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 {
-  if (_Jv_PthreadCheckMonitor (mu))
+  if (_Jv_MutexCheckMonitor (mu))
     return _JV_NOT_OWNER;
 
   _Jv_Thread_t *target;
Index: include/no-threads.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/include/no-threads.h,v
retrieving revision 1.6
diff -u -w -r1.6 no-threads.h
--- include/no-threads.h	22 May 2001 06:47:48 -0000	1.6
+++ include/no-threads.h	17 Oct 2003 01:44:30 -0000
@@ -75,6 +75,11 @@
 // Mutexes.
 //
 
+inline int _Jv_MutexCheckMonitor (_Jv_Mutex_t *mu)
+{
+  return 0;
+}
+
 inline void
 _Jv_MutexInit (_Jv_Mutex_t *)
 {
Index: include/posix-threads.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/include/posix-threads.h,v
retrieving revision 1.24
diff -u -w -r1.24 posix-threads.h
--- include/posix-threads.h	5 Jun 2003 15:43:58 -0000	1.24
+++ include/posix-threads.h	17 Oct 2003 01:44:30 -0000
@@ -77,12 +77,9 @@
 // this out.  Returns 0 if the lock is held by the current thread, and
 // 1 otherwise.
 inline int
-_Jv_PthreadCheckMonitor (_Jv_Mutex_t *mu)
+_Jv_MutexCheckMonitor (_Jv_Mutex_t *mu)
 {
-  pthread_t self = pthread_self();
-  if (mu->owner == self)
-    return 0;
-  else return 1;
+  return (mu->owner != pthread_self());
 }
 
 //
@@ -155,7 +152,7 @@
 inline int
 _Jv_MutexUnlock (_Jv_Mutex_t *mu)
 {
-  if (_Jv_PthreadCheckMonitor (mu))
+  if (_Jv_MutexCheckMonitor (mu))
     {
 #     ifdef LOCK_DEBUG
 	fprintf(stderr, "_Jv_MutexUnlock: Not owner\n");
Index: include/win32-threads.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/include/win32-threads.h,v
retrieving revision 1.8
diff -u -w -r1.8 win32-threads.h
--- include/win32-threads.h	19 Sep 2003 08:28:42 -0000	1.8
+++ include/win32-threads.h	17 Oct 2003 01:44:30 -0000
@@ -86,6 +86,12 @@
 // We use CRITICAL_SECTIONs instead of CreateMutex() for better performance
 //
 
+// Returns 0 if the mutex lock is held by the current thread, and 1 otherwise.
+inline int _Jv_MutexCheckMonitor (_Jv_Mutex_t *mu)
+{
+  return (mu->owner != GetCurrentThreadId ( ));
+}
+
 inline void _Jv_MutexInit (_Jv_Mutex_t *mu)
 {
   mu->owner = 0UL;
Index: java/lang/Object.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/java/lang/Object.h,v
retrieving revision 1.10
diff -u -w -r1.10 Object.h
--- java/lang/Object.h	14 Dec 2001 18:43:53 -0000	1.10
+++ java/lang/Object.h	17 Oct 2003 01:44:30 -0000
@@ -49,6 +49,7 @@
   friend void _Jv_MonitorExit (jobject obj);
   friend void _Jv_InitializeSyncMutex (void);
   friend void _Jv_FinalizeObject (jobject obj);
+  friend bool _Jv_ObjectCheckMonitor (jobject obj);
 
 #ifdef JV_MARKOBJ_DECL
   friend JV_MARKOBJ_DECL;
Index: java/lang/Thread.java
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/java/lang/Thread.java,v
retrieving revision 1.27
diff -u -w -r1.27 Thread.java
--- java/lang/Thread.java	7 Aug 2003 01:12:27 -0000	1.27
+++ java/lang/Thread.java	17 Oct 2003 01:44:30 -0000
@@ -182,6 +182,15 @@
   }
 
   /**
+   * Return true if this Thread holds the object's lock, false otherwise.
+   *
+   * @param obj the object to test lock ownership on.
+   * @throws NullPointerException if obj is null.
+   * @since 1.4
+   */
+  public static native boolean holdsLock (Object obj);
+
+  /**
    * Interrupt this Thread. First, there is a security check,
    * <code>checkAccess</code>. Then, depending on the current state of the
    * thread, various actions take place:
Index: java/lang/natObject.cc
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/java/lang/natObject.cc,v
retrieving revision 1.27
diff -u -w -r1.27 natObject.cc
--- java/lang/natObject.cc	15 Mar 2003 01:04:08 -0000	1.27
+++ java/lang/natObject.cc	17 Oct 2003 01:44:31 -0000
@@ -264,6 +264,13 @@
     throw new java::lang::IllegalMonitorStateException;
 }
 
+bool
+_Jv_ObjectCheckMonitor (jobject obj)
+{
+  _Jv_SyncInfo *si = (_Jv_SyncInfo *) obj->sync_info;
+  return _Jv_MutexCheckMonitor (&si->mutex);
+}
+
 #else /* JV_HASH_SYNCHRONIZATION */
 
 // FIXME: We shouldn't be calling GC_register_finalizer directly.
@@ -1086,6 +1093,45 @@
     }
   keep_live(addr);
 }     
+
+// Return false if obj's monitor is held by the current thread
+bool
+_Jv_ObjectCheckMonitor (jobject obj)
+{
+#ifdef JV_LINKER_CANNOT_8BYTE_ALIGN_STATICS
+  obj_addr_t addr = (obj_addr_t)obj & ~((obj_addr_t)FLAGS);
+#else
+  obj_addr_t addr = (obj_addr_t)obj;
+#endif
+  obj_addr_t address;
+  unsigned hash = JV_SYNC_HASH(addr);
+  hash_entry * he = light_locks + hash;
+  _Jv_ThreadId_t self = _Jv_ThreadSelf();
+
+  JvAssert(!(addr & FLAGS));
+retry:
+  // Acquire the hash table entry lock
+  address = ((he -> address) & ~LOCKED);
+  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
+    {
+      wait_unlocked(he);
+      goto retry;
+    }
+
+  bool not_mine;
+
+  if (!(address & ~FLAGS))
+    not_mine = true;
+  else if ((address & ~FLAGS) == addr)
+    not_mine = (he -> light_thr_id != self);
+  else {
+    heavy_lock* hl = find_heavy(addr, he);
+    not_mine = hl ? (hl->si.mutex.owner != self) : true;
+  }
+
+  release_set(&(he -> address), address);	// unlock hash entry
+  return not_mine;
+}
 
 // The rest of these are moderately thin veneers on _Jv_Cond ops.
 // The current version of Notify might be able to make the pthread
Index: java/lang/natThread.cc
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/java/lang/natThread.cc,v
retrieving revision 1.24
diff -u -w -r1.24 natThread.cc
--- java/lang/natThread.cc	10 Apr 2002 20:36:04 -0000	1.24
+++ java/lang/natThread.cc	17 Oct 2003 01:44:31 -0000
@@ -107,6 +107,14 @@
     (JvNewStringLatin1 ("Thread.destroy unimplemented"));
 }
 
+jboolean
+java::lang::Thread::holdsLock (jobject obj)
+{
+  if (!obj)
+    throw new NullPointerException;
+  return !_Jv_ObjectCheckMonitor (obj);
+}
+
 void
 java::lang::Thread::interrupt (void)
 {



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