--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/jniHandles.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,613 @@
+/*
+ * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "logging/log.hpp"
+#include "memory/iterator.hpp"
+#include "oops/oop.inline.hpp"
+#include "prims/jvmtiExport.hpp"
+#include "runtime/jniHandles.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "runtime/thread.inline.hpp"
+#include "utilities/align.hpp"
+#if INCLUDE_ALL_GCS
+#include "gc/g1/g1SATBCardTableModRefBS.hpp"
+#endif
+
+JNIHandleBlock* JNIHandles::_global_handles = NULL;
+JNIHandleBlock* JNIHandles::_weak_global_handles = NULL;
+oop JNIHandles::_deleted_handle = NULL;
+
+
+jobject JNIHandles::make_local(oop obj) {
+ if (obj == NULL) {
+ return NULL; // ignore null handles
+ } else {
+ Thread* thread = Thread::current();
+ assert(Universe::heap()->is_in_reserved(obj), "sanity check");
+ return thread->active_handles()->allocate_handle(obj);
+ }
+}
+
+
+// optimized versions
+
+jobject JNIHandles::make_local(Thread* thread, oop obj) {
+ if (obj == NULL) {
+ return NULL; // ignore null handles
+ } else {
+ assert(Universe::heap()->is_in_reserved(obj), "sanity check");
+ return thread->active_handles()->allocate_handle(obj);
+ }
+}
+
+
+jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
+ if (obj == NULL) {
+ return NULL; // ignore null handles
+ } else {
+ JavaThread* thread = JavaThread::thread_from_jni_environment(env);
+ assert(Universe::heap()->is_in_reserved(obj), "sanity check");
+ return thread->active_handles()->allocate_handle(obj);
+ }
+}
+
+
+jobject JNIHandles::make_global(Handle obj) {
+ assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
+ jobject res = NULL;
+ if (!obj.is_null()) {
+ // ignore null handles
+ MutexLocker ml(JNIGlobalHandle_lock);
+ assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
+ res = _global_handles->allocate_handle(obj());
+ } else {
+ CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
+ }
+
+ return res;
+}
+
+
+jobject JNIHandles::make_weak_global(Handle obj) {
+ assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
+ jobject res = NULL;
+ if (!obj.is_null()) {
+ // ignore null handles
+ {
+ MutexLocker ml(JNIGlobalHandle_lock);
+ assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
+ res = _weak_global_handles->allocate_handle(obj());
+ }
+ // Add weak tag.
+ assert(is_aligned(res, weak_tag_alignment), "invariant");
+ char* tptr = reinterpret_cast<char*>(res) + weak_tag_value;
+ res = reinterpret_cast<jobject>(tptr);
+ } else {
+ CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
+ }
+ return res;
+}
+
+template<bool external_guard>
+oop JNIHandles::resolve_jweak(jweak handle) {
+ assert(is_jweak(handle), "precondition");
+ oop result = jweak_ref(handle);
+ result = guard_value<external_guard>(result);
+#if INCLUDE_ALL_GCS
+ if (result != NULL && UseG1GC) {
+ G1SATBCardTableModRefBS::enqueue(result);
+ }
+#endif // INCLUDE_ALL_GCS
+ return result;
+}
+
+template oop JNIHandles::resolve_jweak<true>(jweak);
+template oop JNIHandles::resolve_jweak<false>(jweak);
+
+void JNIHandles::destroy_global(jobject handle) {
+ if (handle != NULL) {
+ assert(is_global_handle(handle), "Invalid delete of global JNI handle");
+ jobject_ref(handle) = deleted_handle();
+ }
+}
+
+
+void JNIHandles::destroy_weak_global(jobject handle) {
+ if (handle != NULL) {
+ jweak_ref(handle) = deleted_handle();
+ }
+}
+
+
+void JNIHandles::oops_do(OopClosure* f) {
+ f->do_oop(&_deleted_handle);
+ _global_handles->oops_do(f);
+}
+
+
+void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
+ _weak_global_handles->weak_oops_do(is_alive, f);
+}
+
+
+void JNIHandles::weak_oops_do(OopClosure* f) {
+ AlwaysTrueClosure always_true;
+ weak_oops_do(&always_true, f);
+}
+
+
+void JNIHandles::initialize() {
+ _global_handles = JNIHandleBlock::allocate_block();
+ _weak_global_handles = JNIHandleBlock::allocate_block();
+ EXCEPTION_MARK;
+ // We will never reach the CATCH below since Exceptions::_throw will cause
+ // the VM to exit if an exception is thrown during initialization
+ Klass* k = SystemDictionary::Object_klass();
+ _deleted_handle = InstanceKlass::cast(k)->allocate_instance(CATCH);
+}
+
+
+bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
+ JNIHandleBlock* block = thread->active_handles();
+
+ // Look back past possible native calls to jni_PushLocalFrame.
+ while (block != NULL) {
+ if (block->chain_contains(handle)) {
+ return true;
+ }
+ block = block->pop_frame_link();
+ }
+ return false;
+}
+
+
+// Determine if the handle is somewhere in the current thread's stack.
+// We easily can't isolate any particular stack frame the handle might
+// come from, so we'll check the whole stack.
+
+bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) {
+ // If there is no java frame, then this must be top level code, such
+ // as the java command executable, in which case, this type of handle
+ // is not permitted.
+ return (thr->has_last_Java_frame() &&
+ (void*)obj < (void*)thr->stack_base() &&
+ (void*)obj >= (void*)thr->last_Java_sp());
+}
+
+
+bool JNIHandles::is_global_handle(jobject handle) {
+ return _global_handles->chain_contains(handle);
+}
+
+
+bool JNIHandles::is_weak_global_handle(jobject handle) {
+ return _weak_global_handles->chain_contains(handle);
+}
+
+long JNIHandles::global_handle_memory_usage() {
+ return _global_handles->memory_usage();
+}
+
+long JNIHandles::weak_global_handle_memory_usage() {
+ return _weak_global_handles->memory_usage();
+}
+
+
+class CountHandleClosure: public OopClosure {
+private:
+ int _count;
+public:
+ CountHandleClosure(): _count(0) {}
+ virtual void do_oop(oop* ooph) {
+ if (*ooph != JNIHandles::deleted_handle()) {
+ _count++;
+ }
+ }
+ virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
+ int count() { return _count; }
+};
+
+// We assume this is called at a safepoint: no lock is needed.
+void JNIHandles::print_on(outputStream* st) {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ assert(_global_handles != NULL && _weak_global_handles != NULL,
+ "JNIHandles not initialized");
+
+ CountHandleClosure global_handle_count;
+ oops_do(&global_handle_count);
+ weak_oops_do(&global_handle_count);
+
+ st->print_cr("JNI global references: %d", global_handle_count.count());
+ st->cr();
+ st->flush();
+}
+
+class VerifyHandleClosure: public OopClosure {
+public:
+ virtual void do_oop(oop* root) {
+ (*root)->verify();
+ }
+ virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
+};
+
+void JNIHandles::verify() {
+ VerifyHandleClosure verify_handle;
+
+ oops_do(&verify_handle);
+ weak_oops_do(&verify_handle);
+}
+
+
+
+void jni_handles_init() {
+ JNIHandles::initialize();
+}
+
+
+int JNIHandleBlock::_blocks_allocated = 0;
+JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
+#ifndef PRODUCT
+JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
+#endif
+
+
+void JNIHandleBlock::zap() {
+ // Zap block values
+ _top = 0;
+ for (int index = 0; index < block_size_in_oops; index++) {
+ _handles[index] = badJNIHandle;
+ }
+}
+
+JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
+ assert(thread == NULL || thread == Thread::current(), "sanity check");
+ JNIHandleBlock* block;
+ // Check the thread-local free list for a block so we don't
+ // have to acquire a mutex.
+ if (thread != NULL && thread->free_handle_block() != NULL) {
+ block = thread->free_handle_block();
+ thread->set_free_handle_block(block->_next);
+ }
+ else {
+ // locking with safepoint checking introduces a potential deadlock:
+ // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
+ // - another would hold Threads_lock (jni_AttachCurrentThread) and then
+ // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
+ MutexLockerEx ml(JNIHandleBlockFreeList_lock,
+ Mutex::_no_safepoint_check_flag);
+ if (_block_free_list == NULL) {
+ // Allocate new block
+ block = new JNIHandleBlock();
+ _blocks_allocated++;
+ if (ZapJNIHandleArea) block->zap();
+ #ifndef PRODUCT
+ // Link new block to list of all allocated blocks
+ block->_block_list_link = _block_list;
+ _block_list = block;
+ #endif
+ } else {
+ // Get block from free list
+ block = _block_free_list;
+ _block_free_list = _block_free_list->_next;
+ }
+ }
+ block->_top = 0;
+ block->_next = NULL;
+ block->_pop_frame_link = NULL;
+ block->_planned_capacity = block_size_in_oops;
+ // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
+ debug_only(block->_last = NULL);
+ debug_only(block->_free_list = NULL);
+ debug_only(block->_allocate_before_rebuild = -1);
+ return block;
+}
+
+
+void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
+ assert(thread == NULL || thread == Thread::current(), "sanity check");
+ JNIHandleBlock* pop_frame_link = block->pop_frame_link();
+ // Put returned block at the beginning of the thread-local free list.
+ // Note that if thread == NULL, we use it as an implicit argument that
+ // we _don't_ want the block to be kept on the free_handle_block.
+ // See for instance JavaThread::exit().
+ if (thread != NULL ) {
+ if (ZapJNIHandleArea) block->zap();
+ JNIHandleBlock* freelist = thread->free_handle_block();
+ block->_pop_frame_link = NULL;
+ thread->set_free_handle_block(block);
+
+ // Add original freelist to end of chain
+ if ( freelist != NULL ) {
+ while ( block->_next != NULL ) block = block->_next;
+ block->_next = freelist;
+ }
+ block = NULL;
+ }
+ if (block != NULL) {
+ // Return blocks to free list
+ // locking with safepoint checking introduces a potential deadlock:
+ // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
+ // - another would hold Threads_lock (jni_AttachCurrentThread) and then
+ // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
+ MutexLockerEx ml(JNIHandleBlockFreeList_lock,
+ Mutex::_no_safepoint_check_flag);
+ while (block != NULL) {
+ if (ZapJNIHandleArea) block->zap();
+ JNIHandleBlock* next = block->_next;
+ block->_next = _block_free_list;
+ _block_free_list = block;
+ block = next;
+ }
+ }
+ if (pop_frame_link != NULL) {
+ // As a sanity check we release blocks pointed to by the pop_frame_link.
+ // This should never happen (only if PopLocalFrame is not called the
+ // correct number of times).
+ release_block(pop_frame_link, thread);
+ }
+}
+
+
+void JNIHandleBlock::oops_do(OopClosure* f) {
+ JNIHandleBlock* current_chain = this;
+ // Iterate over chain of blocks, followed by chains linked through the
+ // pop frame links.
+ while (current_chain != NULL) {
+ for (JNIHandleBlock* current = current_chain; current != NULL;
+ current = current->_next) {
+ assert(current == current_chain || current->pop_frame_link() == NULL,
+ "only blocks first in chain should have pop frame link set");
+ for (int index = 0; index < current->_top; index++) {
+ oop* root = &(current->_handles)[index];
+ oop value = *root;
+ // traverse heap pointers only, not deleted handles or free list
+ // pointers
+ if (value != NULL && Universe::heap()->is_in_reserved(value)) {
+ f->do_oop(root);
+ }
+ }
+ // the next handle block is valid only if current block is full
+ if (current->_top < block_size_in_oops) {
+ break;
+ }
+ }
+ current_chain = current_chain->pop_frame_link();
+ }
+}
+
+
+void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive,
+ OopClosure* f) {
+ for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
+ assert(current->pop_frame_link() == NULL,
+ "blocks holding weak global JNI handles should not have pop frame link set");
+ for (int index = 0; index < current->_top; index++) {
+ oop* root = &(current->_handles)[index];
+ oop value = *root;
+ // traverse heap pointers only, not deleted handles or free list pointers
+ if (value != NULL && Universe::heap()->is_in_reserved(value)) {
+ if (is_alive->do_object_b(value)) {
+ // The weakly referenced object is alive, update pointer
+ f->do_oop(root);
+ } else {
+ // The weakly referenced object is not alive, clear the reference by storing NULL
+ log_develop_trace(gc, ref)("Clearing JNI weak reference (" INTPTR_FORMAT ")", p2i(root));
+ *root = NULL;
+ }
+ }
+ }
+ // the next handle block is valid only if current block is full
+ if (current->_top < block_size_in_oops) {
+ break;
+ }
+ }
+
+ /*
+ * JVMTI data structures may also contain weak oops. The iteration of them
+ * is placed here so that we don't need to add it to each of the collectors.
+ */
+ JvmtiExport::weak_oops_do(is_alive, f);
+}
+
+
+jobject JNIHandleBlock::allocate_handle(oop obj) {
+ assert(Universe::heap()->is_in_reserved(obj), "sanity check");
+ if (_top == 0) {
+ // This is the first allocation or the initial block got zapped when
+ // entering a native function. If we have any following blocks they are
+ // not valid anymore.
+ for (JNIHandleBlock* current = _next; current != NULL;
+ current = current->_next) {
+ assert(current->_last == NULL, "only first block should have _last set");
+ assert(current->_free_list == NULL,
+ "only first block should have _free_list set");
+ if (current->_top == 0) {
+ // All blocks after the first clear trailing block are already cleared.
+#ifdef ASSERT
+ for (current = current->_next; current != NULL; current = current->_next) {
+ assert(current->_top == 0, "trailing blocks must already be cleared");
+ }
+#endif
+ break;
+ }
+ current->_top = 0;
+ if (ZapJNIHandleArea) current->zap();
+ }
+ // Clear initial block
+ _free_list = NULL;
+ _allocate_before_rebuild = 0;
+ _last = this;
+ if (ZapJNIHandleArea) zap();
+ }
+
+ // Try last block
+ if (_last->_top < block_size_in_oops) {
+ oop* handle = &(_last->_handles)[_last->_top++];
+ *handle = obj;
+ return (jobject) handle;
+ }
+
+ // Try free list
+ if (_free_list != NULL) {
+ oop* handle = _free_list;
+ _free_list = (oop*) *_free_list;
+ *handle = obj;
+ return (jobject) handle;
+ }
+ // Check if unused block follow last
+ if (_last->_next != NULL) {
+ // update last and retry
+ _last = _last->_next;
+ return allocate_handle(obj);
+ }
+
+ // No space available, we have to rebuild free list or expand
+ if (_allocate_before_rebuild == 0) {
+ rebuild_free_list(); // updates _allocate_before_rebuild counter
+ } else {
+ // Append new block
+ Thread* thread = Thread::current();
+ Handle obj_handle(thread, obj);
+ // This can block, so we need to preserve obj across call.
+ _last->_next = JNIHandleBlock::allocate_block(thread);
+ _last = _last->_next;
+ _allocate_before_rebuild--;
+ obj = obj_handle();
+ }
+ return allocate_handle(obj); // retry
+}
+
+void JNIHandleBlock::release_handle(jobject h) {
+ if (h != NULL) {
+ assert(chain_contains(h), "does not contain the JNI handle");
+ // Mark the handle as deleted, allocate will reuse it
+ *((oop*)h) = JNIHandles::deleted_handle();
+ }
+}
+
+
+void JNIHandleBlock::rebuild_free_list() {
+ assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
+ int free = 0;
+ int blocks = 0;
+ for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
+ for (int index = 0; index < current->_top; index++) {
+ oop* handle = &(current->_handles)[index];
+ if (*handle == JNIHandles::deleted_handle()) {
+ // this handle was cleared out by a delete call, reuse it
+ *handle = (oop) _free_list;
+ _free_list = handle;
+ free++;
+ }
+ }
+ // we should not rebuild free list if there are unused handles at the end
+ assert(current->_top == block_size_in_oops, "just checking");
+ blocks++;
+ }
+ // Heuristic: if more than half of the handles are free we rebuild next time
+ // as well, otherwise we append a corresponding number of new blocks before
+ // attempting a free list rebuild again.
+ int total = blocks * block_size_in_oops;
+ int extra = total - 2*free;
+ if (extra > 0) {
+ // Not as many free handles as we would like - compute number of new blocks to append
+ _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
+ }
+}
+
+
+bool JNIHandleBlock::contains(jobject handle) const {
+ return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
+}
+
+
+bool JNIHandleBlock::chain_contains(jobject handle) const {
+ for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
+ if (current->contains(handle)) {
+ return true;
+ }
+ }
+ return false;
+}
+
+
+int JNIHandleBlock::length() const {
+ int result = 1;
+ for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
+ result++;
+ }
+ return result;
+}
+
+const size_t JNIHandleBlock::get_number_of_live_handles() {
+ CountHandleClosure counter;
+ oops_do(&counter);
+ return counter.count();
+}
+
+// This method is not thread-safe, i.e., must be called while holding a lock on the
+// structure.
+long JNIHandleBlock::memory_usage() const {
+ return length() * sizeof(JNIHandleBlock);
+}
+
+
+#ifndef PRODUCT
+
+bool JNIHandleBlock::any_contains(jobject handle) {
+ for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
+ if (current->contains(handle)) {
+ return true;
+ }
+ }
+ return false;
+}
+
+void JNIHandleBlock::print_statistics() {
+ int used_blocks = 0;
+ int free_blocks = 0;
+ int used_handles = 0;
+ int free_handles = 0;
+ JNIHandleBlock* block = _block_list;
+ while (block != NULL) {
+ if (block->_top > 0) {
+ used_blocks++;
+ } else {
+ free_blocks++;
+ }
+ used_handles += block->_top;
+ free_handles += (block_size_in_oops - block->_top);
+ block = block->_block_list_link;
+ }
+ tty->print_cr("JNIHandleBlocks statistics");
+ tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
+ tty->print_cr("- blocks in use: %d", used_blocks);
+ tty->print_cr("- blocks free: %d", free_blocks);
+ tty->print_cr("- handles in use: %d", used_handles);
+ tty->print_cr("- handles free: %d", free_handles);
+}
+
+#endif