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/*
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* Copyright 1998-2007 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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# include "incls/_precompiled.incl"
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# include "incls/_jniHandles.cpp.incl"
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JNIHandleBlock* JNIHandles::_global_handles = NULL;
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JNIHandleBlock* JNIHandles::_weak_global_handles = NULL;
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oop JNIHandles::_deleted_handle = NULL;
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jobject JNIHandles::make_local(oop obj) {
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if (obj == NULL) {
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return NULL; // ignore null handles
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} else {
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Thread* thread = Thread::current();
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assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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return thread->active_handles()->allocate_handle(obj);
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}
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}
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// optimized versions
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jobject JNIHandles::make_local(Thread* thread, oop obj) {
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if (obj == NULL) {
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return NULL; // ignore null handles
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} else {
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assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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return thread->active_handles()->allocate_handle(obj);
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}
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}
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jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
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if (obj == NULL) {
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return NULL; // ignore null handles
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} else {
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JavaThread* thread = JavaThread::thread_from_jni_environment(env);
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assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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return thread->active_handles()->allocate_handle(obj);
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}
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}
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jobject JNIHandles::make_global(Handle obj) {
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jobject res = NULL;
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if (!obj.is_null()) {
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// ignore null handles
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MutexLocker ml(JNIGlobalHandle_lock);
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assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
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res = _global_handles->allocate_handle(obj());
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} else {
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CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
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}
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return res;
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}
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jobject JNIHandles::make_weak_global(Handle obj) {
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jobject res = NULL;
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if (!obj.is_null()) {
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// ignore null handles
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MutexLocker ml(JNIGlobalHandle_lock);
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assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
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res = _weak_global_handles->allocate_handle(obj());
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} else {
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CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
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}
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return res;
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}
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jmethodID JNIHandles::make_jmethod_id(methodHandle mh) {
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return (jmethodID) make_weak_global(mh);
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}
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void JNIHandles::change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh) {
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MutexLocker ml(JNIGlobalHandle_lock); // Is this necessary?
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Handle obj = (Handle)mh;
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oop* jobj = (oop*)jmid;
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*jobj = obj();
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}
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void JNIHandles::destroy_global(jobject handle) {
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if (handle != NULL) {
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assert(is_global_handle(handle), "Invalid delete of global JNI handle");
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*((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
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}
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}
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void JNIHandles::destroy_weak_global(jobject handle) {
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if (handle != NULL) {
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assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle");
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*((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
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}
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}
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void JNIHandles::destroy_jmethod_id(jmethodID mid) {
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destroy_weak_global((jobject)mid);
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}
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void JNIHandles::oops_do(OopClosure* f) {
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f->do_oop(&_deleted_handle);
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_global_handles->oops_do(f);
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}
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void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
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_weak_global_handles->weak_oops_do(is_alive, f);
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}
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void JNIHandles::initialize() {
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_global_handles = JNIHandleBlock::allocate_block();
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_weak_global_handles = JNIHandleBlock::allocate_block();
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EXCEPTION_MARK;
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// We will never reach the CATCH below since Exceptions::_throw will cause
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// the VM to exit if an exception is thrown during initialization
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klassOop k = SystemDictionary::object_klass();
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_deleted_handle = instanceKlass::cast(k)->allocate_permanent_instance(CATCH);
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}
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bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
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JNIHandleBlock* block = thread->active_handles();
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// Look back past possible native calls to jni_PushLocalFrame.
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while (block != NULL) {
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if (block->chain_contains(handle)) {
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return true;
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}
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block = block->pop_frame_link();
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}
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return false;
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}
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// Determine if the handle is somewhere in the current thread's stack.
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// We easily can't isolate any particular stack frame the handle might
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// come from, so we'll check the whole stack.
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bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) {
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// If there is no java frame, then this must be top level code, such
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// as the java command executable, in which case, this type of handle
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// is not permitted.
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return (thr->has_last_Java_frame() &&
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(void*)obj < (void*)thr->stack_base() &&
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(void*)obj >= (void*)thr->last_Java_sp());
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}
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bool JNIHandles::is_global_handle(jobject handle) {
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return _global_handles->chain_contains(handle);
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}
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bool JNIHandles::is_weak_global_handle(jobject handle) {
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return _weak_global_handles->chain_contains(handle);
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}
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long JNIHandles::global_handle_memory_usage() {
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return _global_handles->memory_usage();
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}
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long JNIHandles::weak_global_handle_memory_usage() {
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return _weak_global_handles->memory_usage();
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}
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class AlwaysAliveClosure: public BoolObjectClosure {
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public:
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bool do_object_b(oop obj) { return true; }
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void do_object(oop obj) { assert(false, "Don't call"); }
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};
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class CountHandleClosure: public OopClosure {
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private:
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int _count;
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public:
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CountHandleClosure(): _count(0) {}
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void do_oop(oop* unused) {
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_count++;
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}
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int count() { return _count; }
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};
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// We assume this is called at a safepoint: no lock is needed.
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void JNIHandles::print_on(outputStream* st) {
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assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
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assert(_global_handles != NULL && _weak_global_handles != NULL,
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"JNIHandles not initialized");
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CountHandleClosure global_handle_count;
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AlwaysAliveClosure always_alive;
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oops_do(&global_handle_count);
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weak_oops_do(&always_alive, &global_handle_count);
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st->print_cr("JNI global references: %d", global_handle_count.count());
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st->cr();
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st->flush();
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}
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class VerifyHandleClosure: public OopClosure {
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public:
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void do_oop(oop* root) {
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(*root)->verify();
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}
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};
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void JNIHandles::verify() {
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VerifyHandleClosure verify_handle;
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AlwaysAliveClosure always_alive;
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oops_do(&verify_handle);
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weak_oops_do(&always_alive, &verify_handle);
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}
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void jni_handles_init() {
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JNIHandles::initialize();
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}
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int JNIHandleBlock::_blocks_allocated = 0;
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JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
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#ifndef PRODUCT
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JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
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#endif
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void JNIHandleBlock::zap() {
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// Zap block values
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_top = 0;
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for (int index = 0; index < block_size_in_oops; index++) {
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_handles[index] = badJNIHandle;
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}
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}
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JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
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assert(thread == NULL || thread == Thread::current(), "sanity check");
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JNIHandleBlock* block;
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// Check the thread-local free list for a block so we don't
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// have to acquire a mutex.
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if (thread != NULL && thread->free_handle_block() != NULL) {
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block = thread->free_handle_block();
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thread->set_free_handle_block(block->_next);
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}
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else {
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// locking with safepoint checking introduces a potential deadlock:
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// - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
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// - another would hold Threads_lock (jni_AttachCurrentThread) and then
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// JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
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MutexLockerEx ml(JNIHandleBlockFreeList_lock,
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Mutex::_no_safepoint_check_flag);
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if (_block_free_list == NULL) {
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// Allocate new block
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block = new JNIHandleBlock();
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_blocks_allocated++;
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if (TraceJNIHandleAllocation) {
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tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)",
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block, _blocks_allocated);
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}
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if (ZapJNIHandleArea) block->zap();
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#ifndef PRODUCT
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// Link new block to list of all allocated blocks
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block->_block_list_link = _block_list;
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_block_list = block;
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#endif
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} else {
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// Get block from free list
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block = _block_free_list;
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_block_free_list = _block_free_list->_next;
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}
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}
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block->_top = 0;
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block->_next = NULL;
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block->_pop_frame_link = NULL;
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// _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
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debug_only(block->_last = NULL);
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debug_only(block->_free_list = NULL);
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debug_only(block->_allocate_before_rebuild = -1);
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return block;
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}
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void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
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assert(thread == NULL || thread == Thread::current(), "sanity check");
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JNIHandleBlock* pop_frame_link = block->pop_frame_link();
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// Put returned block at the beginning of the thread-local free list.
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// Note that if thread == NULL, we use it as an implicit argument that
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// we _don't_ want the block to be kept on the free_handle_block.
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// See for instance JavaThread::exit().
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if (thread != NULL ) {
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if (ZapJNIHandleArea) block->zap();
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JNIHandleBlock* freelist = thread->free_handle_block();
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block->_pop_frame_link = NULL;
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thread->set_free_handle_block(block);
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// Add original freelist to end of chain
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if ( freelist != NULL ) {
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while ( block->_next != NULL ) block = block->_next;
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block->_next = freelist;
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}
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block = NULL;
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}
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if (block != NULL) {
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// Return blocks to free list
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// locking with safepoint checking introduces a potential deadlock:
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// - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
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// - another would hold Threads_lock (jni_AttachCurrentThread) and then
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// JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
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MutexLockerEx ml(JNIHandleBlockFreeList_lock,
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Mutex::_no_safepoint_check_flag);
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while (block != NULL) {
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if (ZapJNIHandleArea) block->zap();
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JNIHandleBlock* next = block->_next;
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block->_next = _block_free_list;
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_block_free_list = block;
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block = next;
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}
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}
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if (pop_frame_link != NULL) {
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// As a sanity check we release blocks pointed to by the pop_frame_link.
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// This should never happen (only if PopLocalFrame is not called the
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// correct number of times).
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release_block(pop_frame_link, thread);
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}
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}
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void JNIHandleBlock::oops_do(OopClosure* f) {
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JNIHandleBlock* current_chain = this;
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// Iterate over chain of blocks, followed by chains linked through the
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// pop frame links.
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while (current_chain != NULL) {
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for (JNIHandleBlock* current = current_chain; current != NULL;
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current = current->_next) {
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assert(current == current_chain || current->pop_frame_link() == NULL,
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"only blocks first in chain should have pop frame link set");
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for (int index = 0; index < current->_top; index++) {
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oop* root = &(current->_handles)[index];
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oop value = *root;
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// traverse heap pointers only, not deleted handles or free list
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// pointers
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if (value != NULL && Universe::heap()->is_in_reserved(value)) {
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f->do_oop(root);
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}
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}
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// the next handle block is valid only if current block is full
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if (current->_top < block_size_in_oops) {
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break;
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}
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}
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current_chain = current_chain->pop_frame_link();
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}
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}
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void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive,
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OopClosure* f) {
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for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
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assert(current->pop_frame_link() == NULL,
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"blocks holding weak global JNI handles should not have pop frame link set");
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for (int index = 0; index < current->_top; index++) {
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oop* root = &(current->_handles)[index];
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oop value = *root;
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// traverse heap pointers only, not deleted handles or free list pointers
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if (value != NULL && Universe::heap()->is_in_reserved(value)) {
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if (is_alive->do_object_b(value)) {
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// The weakly referenced object is alive, update pointer
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f->do_oop(root);
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} else {
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// The weakly referenced object is not alive, clear the reference by storing NULL
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403 |
if (TraceReferenceGC) {
|
|
404 |
tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root);
|
|
405 |
}
|
|
406 |
*root = NULL;
|
|
407 |
}
|
|
408 |
}
|
|
409 |
}
|
|
410 |
// the next handle block is valid only if current block is full
|
|
411 |
if (current->_top < block_size_in_oops) {
|
|
412 |
break;
|
|
413 |
}
|
|
414 |
}
|
|
415 |
}
|
|
416 |
|
|
417 |
|
|
418 |
jobject JNIHandleBlock::allocate_handle(oop obj) {
|
|
419 |
assert(Universe::heap()->is_in_reserved(obj), "sanity check");
|
|
420 |
if (_top == 0) {
|
|
421 |
// This is the first allocation or the initial block got zapped when
|
|
422 |
// entering a native function. If we have any following blocks they are
|
|
423 |
// not valid anymore.
|
|
424 |
for (JNIHandleBlock* current = _next; current != NULL;
|
|
425 |
current = current->_next) {
|
|
426 |
assert(current->_last == NULL, "only first block should have _last set");
|
|
427 |
assert(current->_free_list == NULL,
|
|
428 |
"only first block should have _free_list set");
|
|
429 |
current->_top = 0;
|
|
430 |
if (ZapJNIHandleArea) current->zap();
|
|
431 |
}
|
|
432 |
// Clear initial block
|
|
433 |
_free_list = NULL;
|
|
434 |
_allocate_before_rebuild = 0;
|
|
435 |
_last = this;
|
|
436 |
if (ZapJNIHandleArea) zap();
|
|
437 |
}
|
|
438 |
|
|
439 |
// Try last block
|
|
440 |
if (_last->_top < block_size_in_oops) {
|
|
441 |
oop* handle = &(_last->_handles)[_last->_top++];
|
|
442 |
*handle = obj;
|
|
443 |
return (jobject) handle;
|
|
444 |
}
|
|
445 |
|
|
446 |
// Try free list
|
|
447 |
if (_free_list != NULL) {
|
|
448 |
oop* handle = _free_list;
|
|
449 |
_free_list = (oop*) *_free_list;
|
|
450 |
*handle = obj;
|
|
451 |
return (jobject) handle;
|
|
452 |
}
|
|
453 |
// Check if unused block follow last
|
|
454 |
if (_last->_next != NULL) {
|
|
455 |
// update last and retry
|
|
456 |
_last = _last->_next;
|
|
457 |
return allocate_handle(obj);
|
|
458 |
}
|
|
459 |
|
|
460 |
// No space available, we have to rebuild free list or expand
|
|
461 |
if (_allocate_before_rebuild == 0) {
|
|
462 |
rebuild_free_list(); // updates _allocate_before_rebuild counter
|
|
463 |
} else {
|
|
464 |
// Append new block
|
|
465 |
Thread* thread = Thread::current();
|
|
466 |
Handle obj_handle(thread, obj);
|
|
467 |
// This can block, so we need to preserve obj accross call.
|
|
468 |
_last->_next = JNIHandleBlock::allocate_block(thread);
|
|
469 |
_last = _last->_next;
|
|
470 |
_allocate_before_rebuild--;
|
|
471 |
obj = obj_handle();
|
|
472 |
}
|
|
473 |
return allocate_handle(obj); // retry
|
|
474 |
}
|
|
475 |
|
|
476 |
|
|
477 |
void JNIHandleBlock::rebuild_free_list() {
|
|
478 |
assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
|
|
479 |
int free = 0;
|
|
480 |
int blocks = 0;
|
|
481 |
for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
|
|
482 |
for (int index = 0; index < current->_top; index++) {
|
|
483 |
oop* handle = &(current->_handles)[index];
|
|
484 |
if (*handle == JNIHandles::deleted_handle()) {
|
|
485 |
// this handle was cleared out by a delete call, reuse it
|
|
486 |
*handle = (oop) _free_list;
|
|
487 |
_free_list = handle;
|
|
488 |
free++;
|
|
489 |
}
|
|
490 |
}
|
|
491 |
// we should not rebuild free list if there are unused handles at the end
|
|
492 |
assert(current->_top == block_size_in_oops, "just checking");
|
|
493 |
blocks++;
|
|
494 |
}
|
|
495 |
// Heuristic: if more than half of the handles are free we rebuild next time
|
|
496 |
// as well, otherwise we append a corresponding number of new blocks before
|
|
497 |
// attempting a free list rebuild again.
|
|
498 |
int total = blocks * block_size_in_oops;
|
|
499 |
int extra = total - 2*free;
|
|
500 |
if (extra > 0) {
|
|
501 |
// Not as many free handles as we would like - compute number of new blocks to append
|
|
502 |
_allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
|
|
503 |
}
|
|
504 |
if (TraceJNIHandleAllocation) {
|
|
505 |
tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d",
|
|
506 |
this, blocks, total-free, free, _allocate_before_rebuild);
|
|
507 |
}
|
|
508 |
}
|
|
509 |
|
|
510 |
|
|
511 |
bool JNIHandleBlock::contains(jobject handle) const {
|
|
512 |
return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
|
|
513 |
}
|
|
514 |
|
|
515 |
|
|
516 |
bool JNIHandleBlock::chain_contains(jobject handle) const {
|
|
517 |
for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
|
|
518 |
if (current->contains(handle)) {
|
|
519 |
return true;
|
|
520 |
}
|
|
521 |
}
|
|
522 |
return false;
|
|
523 |
}
|
|
524 |
|
|
525 |
|
|
526 |
int JNIHandleBlock::length() const {
|
|
527 |
int result = 1;
|
|
528 |
for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
|
|
529 |
result++;
|
|
530 |
}
|
|
531 |
return result;
|
|
532 |
}
|
|
533 |
|
|
534 |
// This method is not thread-safe, i.e., must be called whule holding a lock on the
|
|
535 |
// structure.
|
|
536 |
long JNIHandleBlock::memory_usage() const {
|
|
537 |
return length() * sizeof(JNIHandleBlock);
|
|
538 |
}
|
|
539 |
|
|
540 |
|
|
541 |
#ifndef PRODUCT
|
|
542 |
|
|
543 |
bool JNIHandleBlock::any_contains(jobject handle) {
|
|
544 |
for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
|
|
545 |
if (current->contains(handle)) {
|
|
546 |
return true;
|
|
547 |
}
|
|
548 |
}
|
|
549 |
return false;
|
|
550 |
}
|
|
551 |
|
|
552 |
void JNIHandleBlock::print_statistics() {
|
|
553 |
int used_blocks = 0;
|
|
554 |
int free_blocks = 0;
|
|
555 |
int used_handles = 0;
|
|
556 |
int free_handles = 0;
|
|
557 |
JNIHandleBlock* block = _block_list;
|
|
558 |
while (block != NULL) {
|
|
559 |
if (block->_top > 0) {
|
|
560 |
used_blocks++;
|
|
561 |
} else {
|
|
562 |
free_blocks++;
|
|
563 |
}
|
|
564 |
used_handles += block->_top;
|
|
565 |
free_handles += (block_size_in_oops - block->_top);
|
|
566 |
block = block->_block_list_link;
|
|
567 |
}
|
|
568 |
tty->print_cr("JNIHandleBlocks statistics");
|
|
569 |
tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
|
|
570 |
tty->print_cr("- blocks in use: %d", used_blocks);
|
|
571 |
tty->print_cr("- blocks free: %d", free_blocks);
|
|
572 |
tty->print_cr("- handles in use: %d", used_handles);
|
|
573 |
tty->print_cr("- handles free: %d", free_handles);
|
|
574 |
}
|
|
575 |
|
|
576 |
#endif
|