1231 lines
38 KiB
C++
1231 lines
38 KiB
C++
// natObject.cc - Implementation of the Object class.
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/* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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#include <config.h>
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#include <string.h>
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#pragma implementation "Object.h"
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#include <gcj/cni.h>
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#include <jvm.h>
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#include <java/lang/Object.h>
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#include <java-threads.h>
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#include <java-signal.h>
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#include <java/lang/CloneNotSupportedException.h>
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#include <java/lang/IllegalArgumentException.h>
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#include <java/lang/IllegalMonitorStateException.h>
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#include <java/lang/InterruptedException.h>
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#include <java/lang/NullPointerException.h>
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#include <java/lang/Class.h>
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#include <java/lang/Cloneable.h>
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#include <java/lang/Thread.h>
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#ifdef LOCK_DEBUG
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# include <stdio.h>
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#endif
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// This is used to represent synchronization information.
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struct _Jv_SyncInfo
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{
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#if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
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// We only need to keep track of initialization state if we can
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// possibly finalize this object.
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bool init;
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#endif
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_Jv_ConditionVariable_t condition;
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_Jv_Mutex_t mutex;
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};
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jclass
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java::lang::Object::getClass (void)
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{
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_Jv_VTable **dt = (_Jv_VTable **) this;
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return (*dt)->clas;
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}
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jint
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java::lang::Object::hashCode (void)
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{
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return _Jv_HashCode (this);
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}
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jobject
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java::lang::Object::clone (void)
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{
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jclass klass = getClass ();
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jobject r;
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jint size;
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// We also clone arrays here. If we put the array code into
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// __JArray, then we'd have to figure out a way to find the array
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// vtbl when creating a new array class. This is easier, if uglier.
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if (klass->isArray())
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{
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__JArray *array = (__JArray *) this;
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jclass comp = getClass()->getComponentType();
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jint eltsize;
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if (comp->isPrimitive())
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{
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r = _Jv_NewPrimArray (comp, array->length);
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eltsize = comp->size();
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}
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else
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{
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r = _Jv_NewObjectArray (array->length, comp, NULL);
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eltsize = sizeof (jobject);
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}
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// We can't use sizeof on __JArray because we must account for
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// alignment of the element type.
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size = (_Jv_GetArrayElementFromElementType (array, comp) - (char *) array
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+ array->length * eltsize);
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}
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else
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{
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if (! java::lang::Cloneable::class$.isAssignableFrom(klass))
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throw new CloneNotSupportedException;
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size = klass->size();
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r = JvAllocObject (klass, size);
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}
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memcpy ((void *) r, (void *) this, size);
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return r;
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}
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void
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_Jv_FinalizeObject (jobject obj)
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{
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// Ignore exceptions. From section 12.6 of the Java Language Spec.
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try
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{
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obj->finalize ();
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}
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catch (java::lang::Throwable *t)
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{
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// Ignore.
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}
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}
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//
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// Synchronization code.
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//
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#ifndef JV_HASH_SYNCHRONIZATION
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// This global is used to make sure that only one thread sets an
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// object's `sync_info' field.
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static _Jv_Mutex_t sync_mutex;
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// This macro is used to see if synchronization initialization is
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// needed.
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#if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
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# define INIT_NEEDED(Obj) (! (Obj)->sync_info \
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|| ! ((_Jv_SyncInfo *) ((Obj)->sync_info))->init)
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#else
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# define INIT_NEEDED(Obj) (! (Obj)->sync_info)
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#endif
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#if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
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// If we have to run a destructor for a sync_info member, then this
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// function is registered as a finalizer for the sync_info.
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static void
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finalize_sync_info (jobject obj)
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{
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) obj;
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#if defined (_Jv_HaveCondDestroy)
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_Jv_CondDestroy (&si->condition);
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#endif
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#if defined (_Jv_HaveMutexDestroy)
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_Jv_MutexDestroy (&si->mutex);
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#endif
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si->init = false;
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}
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#endif
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// This is called to initialize the sync_info element of an object.
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void
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java::lang::Object::sync_init (void)
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{
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_Jv_MutexLock (&sync_mutex);
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// Check again to see if initialization is needed now that we have
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// the lock.
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if (INIT_NEEDED (this))
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{
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// We assume there are no pointers in the sync_info
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// representation.
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_Jv_SyncInfo *si;
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// We always create a new sync_info, even if there is already
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// one available. Any given object can only be finalized once.
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// If we get here and sync_info is not null, then it has already
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// been finalized. So if we just reinitialize the old one,
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// we'll never be able to (re-)destroy the mutex and/or
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// condition variable.
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si = (_Jv_SyncInfo *) _Jv_AllocBytes (sizeof (_Jv_SyncInfo));
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_Jv_MutexInit (&si->mutex);
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_Jv_CondInit (&si->condition);
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#if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
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// Register a finalizer.
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si->init = true;
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_Jv_RegisterFinalizer (si, finalize_sync_info);
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#endif
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sync_info = (jobject) si;
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}
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_Jv_MutexUnlock (&sync_mutex);
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}
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void
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java::lang::Object::notify (void)
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{
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if (__builtin_expect (INIT_NEEDED (this), false))
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sync_init ();
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) sync_info;
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if (__builtin_expect (_Jv_CondNotify (&si->condition, &si->mutex), false))
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throw new IllegalMonitorStateException(JvNewStringLatin1
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("current thread not owner"));
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}
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void
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java::lang::Object::notifyAll (void)
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{
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if (__builtin_expect (INIT_NEEDED (this), false))
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sync_init ();
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) sync_info;
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if (__builtin_expect (_Jv_CondNotifyAll (&si->condition, &si->mutex), false))
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throw new IllegalMonitorStateException(JvNewStringLatin1
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("current thread not owner"));
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}
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void
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java::lang::Object::wait (jlong timeout, jint nanos)
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{
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if (__builtin_expect (INIT_NEEDED (this), false))
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sync_init ();
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if (__builtin_expect (timeout < 0 || nanos < 0 || nanos > 999999, false))
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throw new IllegalArgumentException;
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) sync_info;
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switch (_Jv_CondWait (&si->condition, &si->mutex, timeout, nanos))
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{
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case _JV_NOT_OWNER:
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throw new IllegalMonitorStateException (JvNewStringLatin1
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("current thread not owner"));
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case _JV_INTERRUPTED:
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if (Thread::interrupted ())
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throw new InterruptedException;
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}
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}
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//
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// Some runtime code.
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//
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// This function is called at system startup to initialize the
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// `sync_mutex'.
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void
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_Jv_InitializeSyncMutex (void)
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{
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_Jv_MutexInit (&sync_mutex);
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}
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void
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_Jv_MonitorEnter (jobject obj)
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{
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#ifndef HANDLE_SEGV
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if (__builtin_expect (! obj, false))
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throw new java::lang::NullPointerException;
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#endif
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if (__builtin_expect (INIT_NEEDED (obj), false))
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obj->sync_init ();
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) obj->sync_info;
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_Jv_MutexLock (&si->mutex);
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// FIXME: In the Windows case, this can return a nonzero error code.
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// We should turn that into some exception ...
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}
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void
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_Jv_MonitorExit (jobject obj)
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{
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JvAssert (obj);
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JvAssert (! INIT_NEEDED (obj));
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_Jv_SyncInfo *si = (_Jv_SyncInfo *) obj->sync_info;
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if (__builtin_expect (_Jv_MutexUnlock (&si->mutex), false))
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throw new java::lang::IllegalMonitorStateException;
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}
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#else /* JV_HASH_SYNCHRONIZATION */
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// FIXME: We shouldn't be calling GC_register_finalizer directly.
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#ifndef HAVE_BOEHM_GC
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# error Hash synchronization currently requires boehm-gc
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// That's actually a bit of a lie: It should also work with the null GC,
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// probably even better than the alternative.
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// To really support alternate GCs here, we would need to widen the
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// interface to finalization, since we sometimes have to register a
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// second finalizer for an object that already has one.
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// We might also want to move the GC interface to a .h file, since
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// the number of procedure call levels involved in some of these
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// operations is already ridiculous, and would become worse if we
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// went through the proper intermediaries.
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#else
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# include "gc.h"
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#endif
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// What follows currenly assumes a Linux-like platform.
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// Some of it specifically assumes X86 or IA64 Linux, though that
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// should be easily fixable.
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// A Java monitor implemention based on a table of locks.
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// Each entry in the table describes
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// locks held for objects that hash to that location.
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// This started out as a reimplementation of the technique used in SGIs JVM,
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// for which we obtained permission from SGI.
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// But in fact, this ended up quite different, though some ideas are
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// still shared with the original.
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// It was also influenced by some of the published IBM work,
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// though it also differs in many ways from that.
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// We could speed this up if we had a way to atomically update
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// an entire cache entry, i.e. 2 contiguous words of memory.
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// That would usually be the case with a 32 bit ABI on a 64 bit processor.
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// But we don't currently go out of our way to target those.
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// I don't know how to do much better with a N bit ABI on a processor
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// that can atomically update only N bits at a time.
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// Author: Hans-J. Boehm (Hans_Boehm@hp.com, boehm@acm.org)
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#include <assert.h>
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#include <limits.h>
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#include <unistd.h> // for usleep, sysconf.
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#include <sched.h> // for sched_yield.
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#include <gcj/javaprims.h>
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typedef size_t obj_addr_t; /* Integer type big enough for object */
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/* address. */
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// The following should move to some standard place. Linux-threads
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// already defines roughly these, as do more recent versions of boehm-gc.
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// The problem is that neither exports them.
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#if defined(__GNUC__) && defined(__i386__)
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// Atomically replace *addr by new_val if it was initially equal to old.
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// Return true if the comparison succeeded.
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// Assumed to have acquire semantics, i.e. later memory operations
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// cannot execute before the compare_and_swap finishes.
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inline static bool
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compare_and_swap(volatile obj_addr_t *addr,
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obj_addr_t old,
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obj_addr_t new_val)
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{
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char result;
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__asm__ __volatile__("lock; cmpxchgl %2, %0; setz %1"
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: "=m"(*(addr)), "=q"(result)
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: "r" (new_val), "0"(*(addr)), "a"(old) : "memory");
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return (bool) result;
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}
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// Set *addr to new_val with release semantics, i.e. making sure
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// that prior loads and stores complete before this
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// assignment.
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// On X86, the hardware shouldn't reorder reads and writes,
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// so we just have to convince gcc not to do it either.
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inline static void
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release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
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{
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__asm__ __volatile__(" " : : : "memory");
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*(addr) = new_val;
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}
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// Compare_and_swap with release semantics instead of acquire semantics.
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// On many architecture, the operation makes both guarantees, so the
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// implementation can be the same.
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inline static bool
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compare_and_swap_release(volatile obj_addr_t *addr,
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obj_addr_t old,
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obj_addr_t new_val)
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{
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return compare_and_swap(addr, old, new_val);
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}
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#endif
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#if defined(__GNUC__) && defined(__ia64__) && SIZEOF_VOID_P == 8
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inline static bool
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compare_and_swap(volatile obj_addr_t *addr,
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obj_addr_t old,
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obj_addr_t new_val)
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{
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unsigned long oldval;
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__asm__ __volatile__("mov ar.ccv=%4 ;; cmpxchg8.acq %0=%1,%2,ar.ccv"
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: "=r"(oldval), "=m"(*addr)
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: "r"(new_val), "1"(*addr), "r"(old) : "memory");
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return (oldval == old);
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}
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|
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// The fact that *addr is volatile should cause the compiler to
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// automatically generate an st8.rel.
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inline static void
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release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
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{
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__asm__ __volatile__(" " : : : "memory");
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*(addr) = new_val;
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}
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inline static bool
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compare_and_swap_release(volatile obj_addr_t *addr,
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obj_addr_t old,
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obj_addr_t new_val)
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{
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unsigned long oldval;
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__asm__ __volatile__("mov ar.ccv=%4 ;; cmpxchg8.rel %0=%1,%2,ar.ccv"
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: "=r"(oldval), "=m"(*addr)
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: "r"(new_val), "1"(*addr), "r"(old) : "memory");
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return (oldval == old);
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}
|
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#endif
|
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|
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#if defined(__GNUC__) && defined(__alpha__)
|
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inline static bool
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compare_and_swap(volatile obj_addr_t *addr,
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obj_addr_t old,
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obj_addr_t new_val)
|
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{
|
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unsigned long oldval;
|
||
char result;
|
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__asm__ __volatile__(
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"1:ldq_l %0, %1\n\t" \
|
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"cmpeq %0, %5, %2\n\t" \
|
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"beq %2, 2f\n\t" \
|
||
"mov %3, %0\n\t" \
|
||
"stq_c %0, %1\n\t" \
|
||
"bne %0, 2f\n\t" \
|
||
"br 1b\n\t" \
|
||
"2:mb"
|
||
: "=&r"(oldval), "=m"(*addr), "=&r"(result)
|
||
: "r" (new_val), "m"(*addr), "r"(old) : "memory");
|
||
return (bool) result;
|
||
}
|
||
|
||
inline static void
|
||
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
|
||
{
|
||
__asm__ __volatile__("mb" : : : "memory");
|
||
*(addr) = new_val;
|
||
}
|
||
|
||
inline static bool
|
||
compare_and_swap_release(volatile obj_addr_t *addr,
|
||
obj_addr_t old,
|
||
obj_addr_t new_val)
|
||
{
|
||
return compare_and_swap(addr, old, new_val);
|
||
}
|
||
#endif
|
||
|
||
// Try to determine whether we are on a multiprocessor, i.e. whether
|
||
// spinning may be profitable.
|
||
// This should really use a suitable autoconf macro.
|
||
// False is the conservative answer, though the right one is much better.
|
||
static bool
|
||
is_mp()
|
||
{
|
||
#ifdef _SC_NPROCESSORS_ONLN
|
||
long nprocs = sysconf(_SC_NPROCESSORS_ONLN);
|
||
return (nprocs > 1);
|
||
#else
|
||
return false;
|
||
#endif
|
||
}
|
||
|
||
// A call to keep_live(p) forces p to be accessible to the GC
|
||
// at this point.
|
||
inline static void
|
||
keep_live(obj_addr_t p)
|
||
{
|
||
__asm__ __volatile__("" : : "rm"(p) : "memory");
|
||
}
|
||
|
||
|
||
// Each hash table entry holds a single preallocated "lightweight" lock.
|
||
// In addition, it holds a chain of "heavyweight" locks. Lightweight
|
||
// locks do not support Object.wait(), and are converted to heavyweight
|
||
// status in response to contention. Unlike the SGI scheme, both
|
||
// ligtweight and heavyweight locks in one hash entry can be simultaneously
|
||
// in use. (The SGI scheme requires that we be able to acquire a heavyweight
|
||
// lock on behalf of another thread, and can thus convert a lock we don't
|
||
// hold to heavyweight status. Here we don't insist on that, and thus
|
||
// let the original holder of the lighweight lock keep it.)
|
||
|
||
struct heavy_lock {
|
||
void * reserved_for_gc;
|
||
struct heavy_lock *next; // Hash chain link.
|
||
// The only field traced by GC.
|
||
obj_addr_t address; // Object to which this lock corresponds.
|
||
// Should not be traced by GC.
|
||
_Jv_SyncInfo si;
|
||
// The remaining fields save prior finalization info for
|
||
// the object, which we needed to replace in order to arrange
|
||
// for cleanup of the lock structure.
|
||
GC_finalization_proc old_finalization_proc;
|
||
void * old_client_data;
|
||
};
|
||
|
||
#ifdef LOCK_DEBUG
|
||
void
|
||
print_hl_list(heavy_lock *hl)
|
||
{
|
||
heavy_lock *p = hl;
|
||
for (; 0 != p; p = p->next)
|
||
fprintf (stderr, "(hl = %p, addr = %p)", p, (void *)(p -> address));
|
||
}
|
||
#endif /* LOCK_DEBUG */
|
||
|
||
#if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
|
||
// If we have to run a destructor for a sync_info member, then this
|
||
// function is registered as a finalizer for the sync_info.
|
||
static void
|
||
heavy_lock_finalization_proc (jobject obj)
|
||
{
|
||
heavy_lock *hl = (heavy_lock *) obj;
|
||
#if defined (_Jv_HaveCondDestroy)
|
||
_Jv_CondDestroy (&hl->si.condition);
|
||
#endif
|
||
#if defined (_Jv_HaveMutexDestroy)
|
||
_Jv_MutexDestroy (&hl->si.mutex);
|
||
#endif
|
||
hl->si.init = false;
|
||
}
|
||
#endif /* defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy) */
|
||
|
||
// We convert the lock back to lightweight status when
|
||
// we exit, so that a single contention episode doesn't doom the lock
|
||
// forever. But we also need to make sure that lock structures for dead
|
||
// objects are eventually reclaimed. We do that in a an additional
|
||
// finalizer on the underlying object.
|
||
// Note that if the corresponding object is dead, it is safe to drop
|
||
// the heavy_lock structure from its list. It is not necessarily
|
||
// safe to deallocate it, since the unlock code could still be running.
|
||
|
||
struct hash_entry {
|
||
volatile obj_addr_t address; // Address of object for which lightweight
|
||
// k is held.
|
||
// We assume the 3 low order bits are zero.
|
||
// With the Boehm collector and bitmap
|
||
// allocation, objects of size 4 bytes are
|
||
// broken anyway. Thus this is primarily
|
||
// a constraint on statically allocated
|
||
// objects used for synchronization.
|
||
// This allows us to use the low order
|
||
// bits as follows:
|
||
# define LOCKED 1 // This hash entry is locked, and its
|
||
// state may be invalid.
|
||
// The lock protects both the hash_entry
|
||
// itself (except for the light_count
|
||
// and light_thr_id fields, which
|
||
// are protected by the lightweight
|
||
// lock itself), and any heavy_monitor
|
||
// structures attached to it.
|
||
# define HEAVY 2 // There may be heavyweight locks
|
||
// associated with this cache entry.
|
||
// The lightweight entry is still valid,
|
||
// if the leading bits of the address
|
||
// field are nonzero.
|
||
// Set if heavy_count is > 0 .
|
||
// Stored redundantly so a single
|
||
// compare-and-swap works in the easy case.
|
||
# define REQUEST_CONVERSION 4 // The lightweight lock is held. But
|
||
// one or more other threads have tried
|
||
// to acquire the lock, and hence request
|
||
// conversion to heavyweight status.
|
||
# define FLAGS (LOCKED | HEAVY | REQUEST_CONVERSION)
|
||
volatile _Jv_ThreadId_t light_thr_id;
|
||
// Thr_id of holder of lightweight lock.
|
||
// Only updated by lightweight lock holder.
|
||
// Must be recognizably invalid if the
|
||
// lightweight lock is not held.
|
||
# define INVALID_THREAD_ID 0 // Works for Linux?
|
||
// If zero doesn't work, we have to
|
||
// initialize lock table.
|
||
volatile unsigned short light_count;
|
||
// Number of times the lightweight lock
|
||
// is held minus one. Zero if lightweight
|
||
// lock is not held.
|
||
unsigned short heavy_count; // Total number of times heavyweight locks
|
||
// associated with this hash entry are held
|
||
// or waiting to be acquired.
|
||
// Threads in wait() are included eventhough
|
||
// they have temporarily released the lock.
|
||
struct heavy_lock * heavy_locks;
|
||
// Chain of heavy locks. Protected
|
||
// by lockbit for he. Locks may
|
||
// remain allocated here even if HEAVY
|
||
// is not set and heavy_count is 0.
|
||
// If a lightweight and hevyweight lock
|
||
// correspond to the same address, the
|
||
// lightweight lock is the right one.
|
||
};
|
||
|
||
#ifndef JV_SYNC_TABLE_SZ
|
||
# define JV_SYNC_TABLE_SZ 1024
|
||
#endif
|
||
|
||
hash_entry light_locks[JV_SYNC_TABLE_SZ];
|
||
|
||
#define JV_SYNC_HASH(p) (((long)p ^ ((long)p >> 10)) % JV_SYNC_TABLE_SZ)
|
||
|
||
#ifdef LOCK_DEBUG
|
||
void print_he(hash_entry *he)
|
||
{
|
||
fprintf(stderr, "lock hash entry = %p, index = %d, address = 0x%lx\n"
|
||
"\tlight_thr_id = 0x%lx, light_count = %d, "
|
||
"heavy_count = %d\n\theavy_locks:", he,
|
||
he - light_locks, he -> address, he -> light_thr_id,
|
||
he -> light_count, he -> heavy_count);
|
||
print_hl_list(he -> heavy_locks);
|
||
fprintf(stderr, "\n");
|
||
}
|
||
#endif /* LOCK_DEBUG */
|
||
|
||
// Wait for roughly 2^n units, touching as little memory as possible.
|
||
static void
|
||
spin(unsigned n)
|
||
{
|
||
const unsigned MP_SPINS = 10;
|
||
const unsigned YIELDS = 4;
|
||
const unsigned SPINS_PER_UNIT = 30;
|
||
const unsigned MIN_SLEEP_USECS = 2001; // Shorter times spin under Linux.
|
||
const unsigned MAX_SLEEP_USECS = 200000;
|
||
static unsigned spin_limit = 0;
|
||
static unsigned yield_limit = YIELDS;
|
||
static bool mp = false;
|
||
static bool spin_initialized = false;
|
||
|
||
if (!spin_initialized)
|
||
{
|
||
mp = is_mp();
|
||
if (mp)
|
||
{
|
||
spin_limit = MP_SPINS;
|
||
yield_limit = MP_SPINS + YIELDS;
|
||
}
|
||
spin_initialized = true;
|
||
}
|
||
if (n < spin_limit)
|
||
{
|
||
unsigned i = SPINS_PER_UNIT << n;
|
||
for (; i > 0; --i)
|
||
__asm__ __volatile__("");
|
||
}
|
||
else if (n < yield_limit)
|
||
{
|
||
sched_yield();
|
||
}
|
||
else
|
||
{
|
||
unsigned duration = MIN_SLEEP_USECS << (n - yield_limit);
|
||
if (n >= 15 + yield_limit || duration > MAX_SLEEP_USECS)
|
||
duration = MAX_SLEEP_USECS;
|
||
usleep(duration);
|
||
}
|
||
}
|
||
|
||
// Wait for a hash entry to become unlocked.
|
||
static void
|
||
wait_unlocked (hash_entry *he)
|
||
{
|
||
unsigned i = 0;
|
||
while (he -> address & LOCKED)
|
||
spin (i++);
|
||
}
|
||
|
||
// Return the heavy lock for addr if it was already allocated.
|
||
// The client passes in the appropriate hash_entry.
|
||
// We hold the lock for he.
|
||
static inline heavy_lock *
|
||
find_heavy (obj_addr_t addr, hash_entry *he)
|
||
{
|
||
heavy_lock *hl = he -> heavy_locks;
|
||
while (hl != 0 && hl -> address != addr) hl = hl -> next;
|
||
return hl;
|
||
}
|
||
|
||
// Unlink the heavy lock for the given address from its hash table chain.
|
||
// Dies miserably and conspicuously if it's not there, since that should
|
||
// be impossible.
|
||
static inline void
|
||
unlink_heavy (obj_addr_t addr, hash_entry *he)
|
||
{
|
||
heavy_lock **currentp = &(he -> heavy_locks);
|
||
while ((*currentp) -> address != addr)
|
||
currentp = &((*currentp) -> next);
|
||
*currentp = (*currentp) -> next;
|
||
}
|
||
|
||
// Finalization procedure for objects that have associated heavy-weight
|
||
// locks. This may replace the real finalization procedure.
|
||
static void
|
||
heavy_lock_obj_finalization_proc (void *obj, void *cd)
|
||
{
|
||
heavy_lock *hl = (heavy_lock *)cd;
|
||
obj_addr_t addr = (obj_addr_t)obj;
|
||
GC_finalization_proc old_finalization_proc = hl -> old_finalization_proc;
|
||
void * old_client_data = hl -> old_client_data;
|
||
|
||
if (old_finalization_proc != 0)
|
||
{
|
||
// We still need to run a real finalizer. In an idealized
|
||
// world, in which people write thread-safe finalizers, that is
|
||
// likely to require synchronization. Thus we reregister
|
||
// ourselves as the only finalizer, and simply run the real one.
|
||
// Thus we don't clean up the lock yet, but we're likely to do so
|
||
// on the next GC cycle.
|
||
hl -> old_finalization_proc = 0;
|
||
hl -> old_client_data = 0;
|
||
# ifdef HAVE_BOEHM_GC
|
||
GC_REGISTER_FINALIZER_NO_ORDER(obj, heavy_lock_obj_finalization_proc, cd, 0, 0);
|
||
# endif
|
||
old_finalization_proc(obj, old_client_data);
|
||
}
|
||
else
|
||
{
|
||
// The object is really dead, although it's conceivable that
|
||
// some thread may still be in the process of releasing the
|
||
// heavy lock. Unlink it and, if necessary, register a finalizer
|
||
// to distroy sync_info.
|
||
hash_entry *he = light_locks + JV_SYNC_HASH(addr);
|
||
obj_addr_t address = (he -> address & ~LOCKED);
|
||
while (!compare_and_swap(&(he -> address), address, address | LOCKED ))
|
||
{
|
||
// Hash table entry is currently locked. We can't safely touch
|
||
// touch the list of heavy locks.
|
||
wait_unlocked(he);
|
||
address = (he -> address & ~LOCKED);
|
||
}
|
||
unlink_heavy(addr, light_locks + JV_SYNC_HASH(addr));
|
||
release_set(&(he -> address), address);
|
||
# if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
|
||
// Register a finalizer, yet again.
|
||
hl->si.init = true;
|
||
_Jv_RegisterFinalizer (hl, heavy_lock_finalization_proc);
|
||
# endif
|
||
}
|
||
}
|
||
|
||
// Allocate a new heavy lock for addr, returning its address.
|
||
// Assumes we already have the hash_entry locked, and there
|
||
// is currently no lightweight or allocated lock for addr.
|
||
// We register a finalizer for addr, which is responsible for
|
||
// removing the heavy lock when addr goes away, in addition
|
||
// to the responsibilities of any prior finalizer.
|
||
static heavy_lock *
|
||
alloc_heavy(obj_addr_t addr, hash_entry *he)
|
||
{
|
||
heavy_lock * hl = (heavy_lock *) _Jv_AllocTraceOne(sizeof (heavy_lock));
|
||
|
||
hl -> address = addr;
|
||
_Jv_MutexInit (&(hl -> si.mutex));
|
||
_Jv_CondInit (&(hl -> si.condition));
|
||
# if defined (_Jv_HaveCondDestroy) || defined (_Jv_HaveMutexDestroy)
|
||
hl->si.init = true; // needed ?
|
||
# endif
|
||
hl -> next = he -> heavy_locks;
|
||
he -> heavy_locks = hl;
|
||
// FIXME: The only call that cheats and goes directly to the GC interface.
|
||
# ifdef HAVE_BOEHM_GC
|
||
GC_REGISTER_FINALIZER_NO_ORDER(
|
||
(void *)addr, heavy_lock_obj_finalization_proc,
|
||
hl, &hl->old_finalization_proc,
|
||
&hl->old_client_data);
|
||
# endif /* HAVE_BOEHM_GC */
|
||
return hl;
|
||
}
|
||
|
||
// Return the heavy lock for addr, allocating if necessary.
|
||
// Assumes we have the cache entry locked, and there is no lightweight
|
||
// lock for addr.
|
||
static heavy_lock *
|
||
get_heavy(obj_addr_t addr, hash_entry *he)
|
||
{
|
||
heavy_lock *hl = find_heavy(addr, he);
|
||
if (0 == hl)
|
||
hl = alloc_heavy(addr, he);
|
||
return hl;
|
||
}
|
||
|
||
void
|
||
_Jv_MonitorEnter (jobject obj)
|
||
{
|
||
obj_addr_t addr = (obj_addr_t)obj;
|
||
obj_addr_t address;
|
||
unsigned hash = JV_SYNC_HASH(addr);
|
||
hash_entry * he = light_locks + hash;
|
||
_Jv_ThreadId_t self = _Jv_ThreadSelf();
|
||
unsigned count;
|
||
const unsigned N_SPINS = 18;
|
||
|
||
assert(!(addr & FLAGS));
|
||
retry:
|
||
if (__builtin_expect(compare_and_swap(&(he -> address),
|
||
0, addr),true))
|
||
{
|
||
assert(he -> light_thr_id == INVALID_THREAD_ID);
|
||
assert(he -> light_count == 0);
|
||
he -> light_thr_id = self;
|
||
// Count fields are set correctly. Heavy_count was also zero,
|
||
// but can change asynchronously.
|
||
// This path is hopefully both fast and the most common.
|
||
return;
|
||
}
|
||
address = he -> address;
|
||
if ((address & ~(HEAVY | REQUEST_CONVERSION)) == addr)
|
||
{
|
||
if (he -> light_thr_id == self)
|
||
{
|
||
// We hold the lightweight lock, and it's for the right
|
||
// address.
|
||
count = he -> light_count;
|
||
if (count == USHRT_MAX)
|
||
{
|
||
// I think most JVMs don't check for this.
|
||
// But I'm not convinced I couldn't turn this into a security
|
||
// hole, even with a 32 bit counter.
|
||
throw new java::lang::IllegalMonitorStateException(
|
||
JvNewStringLatin1("maximum monitor nesting level exceeded"));
|
||
}
|
||
he -> light_count = count + 1;
|
||
return;
|
||
}
|
||
else
|
||
{
|
||
// Lightweight lock is held, but by somone else.
|
||
// Spin a few times. This avoids turning this into a heavyweight
|
||
// lock if the current holder is about to release it.
|
||
for (unsigned int i = 0; i < N_SPINS; ++i)
|
||
{
|
||
if ((he -> address & ~LOCKED) != (address & ~LOCKED)) goto retry;
|
||
spin(i);
|
||
}
|
||
address &= ~LOCKED;
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED ))
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
heavy_lock *hl = get_heavy(addr, he);
|
||
++ (he -> heavy_count);
|
||
// The hl lock acquisition can't block for long, since it can
|
||
// only be held by other threads waiting for conversion, and
|
||
// they, like us, drop it quickly without blocking.
|
||
_Jv_MutexLock(&(hl->si.mutex));
|
||
assert(he -> address == address | LOCKED );
|
||
release_set(&(he -> address), (address | REQUEST_CONVERSION | HEAVY));
|
||
// release lock on he
|
||
while ((he -> address & ~FLAGS) == (address & ~FLAGS))
|
||
{
|
||
// Once converted, the lock has to retain heavyweight
|
||
// status, since heavy_count > 0 .
|
||
_Jv_CondWait (&(hl->si.condition), &(hl->si.mutex), 0, 0);
|
||
}
|
||
keep_live(addr);
|
||
// Guarantee that hl doesn't get unlinked by finalizer.
|
||
// This is only an issue if the client fails to release
|
||
// the lock, which is unlikely.
|
||
assert(he -> address & HEAVY);
|
||
// Lock has been converted, we hold the heavyweight lock,
|
||
// heavy_count has been incremented.
|
||
return;
|
||
}
|
||
}
|
||
obj_addr_t was_heavy = (address & HEAVY);
|
||
address &= ~LOCKED;
|
||
if (!compare_and_swap(&(he -> address), address, (address | LOCKED )))
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
if ((address & ~(HEAVY | REQUEST_CONVERSION)) == 0)
|
||
{
|
||
// Either was_heavy is true, or something changed out from under us,
|
||
// since the initial test for 0 failed.
|
||
assert(!(address & REQUEST_CONVERSION));
|
||
// Can't convert a nonexistent lightweight lock.
|
||
heavy_lock *hl;
|
||
hl = (was_heavy? find_heavy(addr, he) : 0);
|
||
if (0 == hl)
|
||
{
|
||
// It is OK to use the lighweight lock, since either the
|
||
// heavyweight lock does not exist, or none of the
|
||
// heavyweight locks currently exist. Future threads
|
||
// trying to acquire the lock will see the lightweight
|
||
// one first and use that.
|
||
he -> light_thr_id = self; // OK, since nobody else can hold
|
||
// light lock or do this at the same time.
|
||
assert(he -> light_count == 0);
|
||
assert(was_heavy == (he -> address & HEAVY));
|
||
release_set(&(he -> address), (addr | was_heavy));
|
||
}
|
||
else
|
||
{
|
||
// Must use heavy lock.
|
||
++ (he -> heavy_count);
|
||
assert(0 == (address & ~HEAVY));
|
||
release_set(&(he -> address), HEAVY);
|
||
_Jv_MutexLock(&(hl->si.mutex));
|
||
keep_live(addr);
|
||
}
|
||
return;
|
||
}
|
||
// Lightweight lock is held, but does not correspond to this object.
|
||
// We hold the lock on the hash entry, and he -> address can't
|
||
// change from under us. Neither can the chain of heavy locks.
|
||
{
|
||
assert(0 == he -> heavy_count || (address & HEAVY));
|
||
heavy_lock *hl = get_heavy(addr, he);
|
||
++ (he -> heavy_count);
|
||
release_set(&(he -> address), address | HEAVY);
|
||
_Jv_MutexLock(&(hl->si.mutex));
|
||
keep_live(addr);
|
||
}
|
||
}
|
||
|
||
|
||
void
|
||
_Jv_MonitorExit (jobject obj)
|
||
{
|
||
obj_addr_t addr = (obj_addr_t)obj;
|
||
_Jv_ThreadId_t self = _Jv_ThreadSelf();
|
||
unsigned hash = JV_SYNC_HASH(addr);
|
||
hash_entry * he = light_locks + hash;
|
||
_Jv_ThreadId_t light_thr_id;
|
||
unsigned count;
|
||
obj_addr_t address;
|
||
|
||
retry:
|
||
light_thr_id = he -> light_thr_id;
|
||
// Unfortunately, it turns out we always need to read the address
|
||
// first. Even if we are going to update it with compare_and_swap,
|
||
// we need to reset light_thr_id, and that's not safe unless we know
|
||
// know that we hold the lock.
|
||
address = he -> address;
|
||
// First the (relatively) fast cases:
|
||
if (__builtin_expect(light_thr_id == self, true))
|
||
{
|
||
count = he -> light_count;
|
||
if (__builtin_expect((address & ~HEAVY) == addr, true))
|
||
{
|
||
if (count != 0)
|
||
{
|
||
// We held the lightweight lock all along. Thus the values
|
||
// we saw for light_thr_id and light_count must have been valid.
|
||
he -> light_count = count - 1;
|
||
return;
|
||
}
|
||
else
|
||
{
|
||
// We hold the lightweight lock once.
|
||
he -> light_thr_id = INVALID_THREAD_ID;
|
||
if (compare_and_swap_release(&(he -> address), address,
|
||
address & HEAVY))
|
||
return;
|
||
else
|
||
{
|
||
he -> light_thr_id = light_thr_id; // Undo prior damage.
|
||
goto retry;
|
||
}
|
||
}
|
||
}
|
||
// else lock is not for this address, conversion is requested,
|
||
// or the lock bit in the address field is set.
|
||
}
|
||
else
|
||
{
|
||
if ((address & ~(HEAVY | REQUEST_CONVERSION)) == addr)
|
||
{
|
||
# ifdef LOCK_DEBUG
|
||
fprintf(stderr, "Lightweight lock held by other thread\n\t"
|
||
"light_thr_id = 0x%lx, self = 0x%lx, "
|
||
"address = 0x%lx, pid = %d\n",
|
||
light_thr_id, self, address, getpid());
|
||
print_he(he);
|
||
for(;;) {}
|
||
# endif
|
||
// Someone holds the lightweight lock for this object, and
|
||
// it can't be us.
|
||
throw new java::lang::IllegalMonitorStateException(
|
||
JvNewStringLatin1("current thread not owner"));
|
||
}
|
||
else
|
||
count = he -> light_count;
|
||
}
|
||
if (address & LOCKED)
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
// Now the unlikely cases.
|
||
// We do know that:
|
||
// - Address is set, and doesn't contain the LOCKED bit.
|
||
// - If address refers to the same object as addr, then he -> light_thr_id
|
||
// refers to this thread, and count is valid.
|
||
// - The case in which we held the lightweight lock has been
|
||
// completely handled, except for the REQUEST_CONVERSION case.
|
||
//
|
||
if ((address & ~FLAGS) == addr)
|
||
{
|
||
// The lightweight lock is assigned to this object.
|
||
// Thus we must be in the REQUEST_CONVERSION case.
|
||
if (0 != count)
|
||
{
|
||
// Defer conversion until we exit completely.
|
||
he -> light_count = count - 1;
|
||
return;
|
||
}
|
||
assert(he -> light_thr_id == self);
|
||
assert(address & REQUEST_CONVERSION);
|
||
// Conversion requested
|
||
// Convert now.
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED))
|
||
goto retry;
|
||
heavy_lock *hl = find_heavy(addr, he);
|
||
assert (0 != hl);
|
||
// Requestor created it.
|
||
he -> light_count = 0;
|
||
assert(he -> heavy_count > 0);
|
||
// was incremented by requestor.
|
||
_Jv_MutexLock(&(hl->si.mutex));
|
||
// Release the he lock after acquiring the mutex.
|
||
// Otherwise we can accidentally
|
||
// notify a thread that has already seen a heavyweight
|
||
// lock.
|
||
he -> light_thr_id = INVALID_THREAD_ID;
|
||
release_set(&(he -> address), HEAVY);
|
||
// lightweight lock now unused.
|
||
_Jv_CondNotifyAll(&(hl->si.condition), &(hl->si.mutex));
|
||
_Jv_MutexUnlock(&(hl->si.mutex));
|
||
// heavy_count was already incremented by original requestor.
|
||
keep_live(addr);
|
||
return;
|
||
}
|
||
// lightweight lock not for this object.
|
||
assert(!(address & LOCKED));
|
||
assert((address & ~FLAGS) != addr);
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED))
|
||
goto retry;
|
||
heavy_lock *hl = find_heavy(addr, he);
|
||
if (NULL == hl)
|
||
{
|
||
# ifdef LOCK_DEBUG
|
||
fprintf(stderr, "Failed to find heavyweight lock for addr 0x%lx"
|
||
" pid = %d\n", addr, getpid());
|
||
print_he(he);
|
||
for(;;) {}
|
||
# endif
|
||
throw new java::lang::IllegalMonitorStateException(
|
||
JvNewStringLatin1("current thread not owner"));
|
||
}
|
||
assert(address & HEAVY);
|
||
count = he -> heavy_count;
|
||
assert(count > 0);
|
||
--count;
|
||
if (0 == count) address &= ~HEAVY;
|
||
he -> heavy_count = count;
|
||
release_set(&(he -> address), address);
|
||
// release lock bit, preserving
|
||
// REQUEST_CONVERSION
|
||
// and object address.
|
||
_Jv_MutexUnlock(&(hl->si.mutex));
|
||
// Unlock after releasing the lock bit, so that
|
||
// we don't switch to another thread prematurely.
|
||
keep_live(addr);
|
||
}
|
||
|
||
// The rest of these are moderately thin veneers on _Jv_Cond ops.
|
||
// The current version of Notify might be able to make the pthread
|
||
// call AFTER releasing the lock, thus saving some context switches??
|
||
|
||
void
|
||
java::lang::Object::wait (jlong timeout, jint nanos)
|
||
{
|
||
obj_addr_t addr = (obj_addr_t)this;
|
||
_Jv_ThreadId_t self = _Jv_ThreadSelf();
|
||
unsigned hash = JV_SYNC_HASH(addr);
|
||
hash_entry * he = light_locks + hash;
|
||
unsigned count;
|
||
obj_addr_t address;
|
||
heavy_lock *hl;
|
||
|
||
if (__builtin_expect (timeout < 0 || nanos < 0 || nanos > 999999, false))
|
||
throw new IllegalArgumentException;
|
||
retry:
|
||
address = he -> address;
|
||
address &= ~LOCKED;
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED))
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
// address does not have the lock bit set. We hold the lock on he.
|
||
if ((address & ~FLAGS) == addr)
|
||
{
|
||
// Convert to heavyweight.
|
||
if (he -> light_thr_id != self)
|
||
{
|
||
# ifdef LOCK_DEBUG
|
||
fprintf(stderr, "Found wrong lightweight lock owner in wait "
|
||
"address = 0x%lx pid = %d\n", address, getpid());
|
||
print_he(he);
|
||
for(;;) {}
|
||
# endif
|
||
release_set(&(he -> address), address);
|
||
throw new IllegalMonitorStateException (JvNewStringLatin1
|
||
("current thread not owner"));
|
||
}
|
||
count = he -> light_count;
|
||
hl = get_heavy(addr, he);
|
||
he -> light_count = 0;
|
||
he -> heavy_count += count + 1;
|
||
for (unsigned i = 0; i <= count; ++i)
|
||
_Jv_MutexLock(&(hl->si.mutex));
|
||
// Again release the he lock after acquiring the mutex.
|
||
he -> light_thr_id = INVALID_THREAD_ID;
|
||
release_set(&(he -> address), HEAVY); // lightweight lock now unused.
|
||
if (address & REQUEST_CONVERSION)
|
||
_Jv_CondNotify (&(hl->si.condition), &(hl->si.mutex));
|
||
}
|
||
else /* We should hold the heavyweight lock. */
|
||
{
|
||
hl = find_heavy(addr, he);
|
||
release_set(&(he -> address), address);
|
||
if (0 == hl)
|
||
{
|
||
# ifdef LOCK_DEBUG
|
||
fprintf(stderr, "Couldn't find heavy lock in wait "
|
||
"addr = 0x%lx pid = %d\n", addr, getpid());
|
||
print_he(he);
|
||
for(;;) {}
|
||
# endif
|
||
throw new IllegalMonitorStateException (JvNewStringLatin1
|
||
("current thread not owner"));
|
||
}
|
||
assert(address & HEAVY);
|
||
}
|
||
switch (_Jv_CondWait (&(hl->si.condition), &(hl->si.mutex), timeout, nanos))
|
||
{
|
||
case _JV_NOT_OWNER:
|
||
throw new IllegalMonitorStateException (JvNewStringLatin1
|
||
("current thread not owner"));
|
||
case _JV_INTERRUPTED:
|
||
if (Thread::interrupted ())
|
||
throw new InterruptedException;
|
||
}
|
||
}
|
||
|
||
void
|
||
java::lang::Object::notify (void)
|
||
{
|
||
obj_addr_t addr = (obj_addr_t)this;
|
||
_Jv_ThreadId_t self = _Jv_ThreadSelf();
|
||
unsigned hash = JV_SYNC_HASH(addr);
|
||
hash_entry * he = light_locks + hash;
|
||
heavy_lock *hl;
|
||
obj_addr_t address;
|
||
int result;
|
||
|
||
retry:
|
||
address = ((he -> address) & ~LOCKED);
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED))
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
if ((address & ~FLAGS) == addr && he -> light_thr_id == self)
|
||
{
|
||
// We hold lightweight lock. Since it has not
|
||
// been inflated, there are no waiters.
|
||
release_set(&(he -> address), address); // unlock
|
||
return;
|
||
}
|
||
hl = find_heavy(addr, he);
|
||
// Hl can't disappear since we point to the underlying object.
|
||
// It's important that we release the lock bit before the notify, since
|
||
// otherwise we will try to wake up thee target while we still hold the
|
||
// bit. This results in lock bit contention, which we don't handle
|
||
// terribly well.
|
||
release_set(&(he -> address), address); // unlock
|
||
if (0 == hl)
|
||
{
|
||
throw new IllegalMonitorStateException(JvNewStringLatin1
|
||
("current thread not owner"));
|
||
return;
|
||
}
|
||
result = _Jv_CondNotify(&(hl->si.condition), &(hl->si.mutex));
|
||
keep_live(addr);
|
||
if (__builtin_expect (result, 0))
|
||
throw new IllegalMonitorStateException(JvNewStringLatin1
|
||
("current thread not owner"));
|
||
}
|
||
|
||
void
|
||
java::lang::Object::notifyAll (void)
|
||
{
|
||
obj_addr_t addr = (obj_addr_t)this;
|
||
_Jv_ThreadId_t self = _Jv_ThreadSelf();
|
||
unsigned hash = JV_SYNC_HASH(addr);
|
||
hash_entry * he = light_locks + hash;
|
||
heavy_lock *hl;
|
||
obj_addr_t address;
|
||
int result;
|
||
|
||
retry:
|
||
address = (he -> address) & ~LOCKED;
|
||
if (!compare_and_swap(&(he -> address), address, address | LOCKED))
|
||
{
|
||
wait_unlocked(he);
|
||
goto retry;
|
||
}
|
||
hl = find_heavy(addr, he);
|
||
if ((address & ~FLAGS) == addr && he -> light_thr_id == self)
|
||
{
|
||
// We hold lightweight lock. Since it has not
|
||
// been inflated, there are no waiters.
|
||
release_set(&(he -> address), address); // unlock
|
||
return;
|
||
}
|
||
release_set(&(he -> address), address); // unlock
|
||
if (0 == hl)
|
||
{
|
||
throw new IllegalMonitorStateException(JvNewStringLatin1
|
||
("current thread not owner"));
|
||
}
|
||
result = _Jv_CondNotifyAll(&(hl->si.condition), &(hl->si.mutex));
|
||
if (__builtin_expect (result, 0))
|
||
throw new IllegalMonitorStateException(JvNewStringLatin1
|
||
("current thread not owner"));
|
||
}
|
||
|
||
// This is declared in Java code and in Object.h.
|
||
// It should never be called with JV_HASH_SYNCHRONIZATION
|
||
void
|
||
java::lang::Object::sync_init (void)
|
||
{
|
||
throw new IllegalMonitorStateException(JvNewStringLatin1
|
||
("internal error: sync_init"));
|
||
}
|
||
|
||
// This is called on startup and declared in Object.h.
|
||
// For now we just make it a no-op.
|
||
void
|
||
_Jv_InitializeSyncMutex (void)
|
||
{
|
||
}
|
||
|
||
#endif /* JV_HASH_SYNCHRONIZATION */
|
||
|