| /* |
| * Copyright (c) 1998, 2016, 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" |
| |
| 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()); |
| } else { |
| CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops()); |
| } |
| return res; |
| } |
| |
| |
| void JNIHandles::destroy_global(jobject handle) { |
| if (handle != NULL) { |
| assert(is_global_handle(handle), "Invalid delete of global JNI handle"); |
| *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it |
| } |
| } |
| |
| |
| void JNIHandles::destroy_weak_global(jobject handle) { |
| if (handle != NULL) { |
| assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle"); |
| *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it |
| } |
| } |
| |
| |
| 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"); |
| 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 |