aoqi@0: /*
poonam@7627:  * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #include "precompiled.hpp"
aoqi@0: #include "classfile/systemDictionary.hpp"
aoqi@0: #include "oops/oop.inline.hpp"
aoqi@0: #include "prims/jvmtiExport.hpp"
aoqi@0: #include "runtime/jniHandles.hpp"
aoqi@0: #include "runtime/mutexLocker.hpp"
aoqi@0: #include "runtime/thread.inline.hpp"
aoqi@0: 
aoqi@0: PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
aoqi@0: 
aoqi@0: JNIHandleBlock* JNIHandles::_global_handles       = NULL;
aoqi@0: JNIHandleBlock* JNIHandles::_weak_global_handles  = NULL;
aoqi@0: oop             JNIHandles::_deleted_handle       = NULL;
aoqi@0: 
aoqi@0: 
aoqi@0: jobject JNIHandles::make_local(oop obj) {
aoqi@0:   if (obj == NULL) {
aoqi@0:     return NULL;                // ignore null handles
aoqi@0:   } else {
aoqi@0:     Thread* thread = Thread::current();
aoqi@0:     assert(Universe::heap()->is_in_reserved(obj), "sanity check");
aoqi@0:     return thread->active_handles()->allocate_handle(obj);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // optimized versions
aoqi@0: 
aoqi@0: jobject JNIHandles::make_local(Thread* thread, oop obj) {
aoqi@0:   if (obj == NULL) {
aoqi@0:     return NULL;                // ignore null handles
aoqi@0:   } else {
aoqi@0:     assert(Universe::heap()->is_in_reserved(obj), "sanity check");
aoqi@0:     return thread->active_handles()->allocate_handle(obj);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
aoqi@0:   if (obj == NULL) {
aoqi@0:     return NULL;                // ignore null handles
aoqi@0:   } else {
aoqi@0:     JavaThread* thread = JavaThread::thread_from_jni_environment(env);
aoqi@0:     assert(Universe::heap()->is_in_reserved(obj), "sanity check");
aoqi@0:     return thread->active_handles()->allocate_handle(obj);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: jobject JNIHandles::make_global(Handle obj) {
aoqi@0:   assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
aoqi@0:   jobject res = NULL;
aoqi@0:   if (!obj.is_null()) {
aoqi@0:     // ignore null handles
aoqi@0:     MutexLocker ml(JNIGlobalHandle_lock);
aoqi@0:     assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
aoqi@0:     res = _global_handles->allocate_handle(obj());
aoqi@0:   } else {
aoqi@0:     CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
aoqi@0:   }
aoqi@0: 
aoqi@0:   return res;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: jobject JNIHandles::make_weak_global(Handle obj) {
aoqi@0:   assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
aoqi@0:   jobject res = NULL;
aoqi@0:   if (!obj.is_null()) {
aoqi@0:     // ignore null handles
aoqi@0:     MutexLocker ml(JNIGlobalHandle_lock);
aoqi@0:     assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
aoqi@0:     res = _weak_global_handles->allocate_handle(obj());
aoqi@0:   } else {
aoqi@0:     CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
aoqi@0:   }
aoqi@0:   return res;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandles::destroy_global(jobject handle) {
aoqi@0:   if (handle != NULL) {
aoqi@0:     assert(is_global_handle(handle), "Invalid delete of global JNI handle");
aoqi@0:     *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandles::destroy_weak_global(jobject handle) {
aoqi@0:   if (handle != NULL) {
aoqi@0:     assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle");
aoqi@0:     *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandles::oops_do(OopClosure* f) {
aoqi@0:   f->do_oop(&_deleted_handle);
aoqi@0:   _global_handles->oops_do(f);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
aoqi@0:   _weak_global_handles->weak_oops_do(is_alive, f);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandles::initialize() {
aoqi@0:   _global_handles      = JNIHandleBlock::allocate_block();
aoqi@0:   _weak_global_handles = JNIHandleBlock::allocate_block();
aoqi@0:   EXCEPTION_MARK;
aoqi@0:   // We will never reach the CATCH below since Exceptions::_throw will cause
aoqi@0:   // the VM to exit if an exception is thrown during initialization
aoqi@0:   Klass* k      = SystemDictionary::Object_klass();
aoqi@0:   _deleted_handle = InstanceKlass::cast(k)->allocate_instance(CATCH);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
aoqi@0:   JNIHandleBlock* block = thread->active_handles();
aoqi@0: 
aoqi@0:   // Look back past possible native calls to jni_PushLocalFrame.
aoqi@0:   while (block != NULL) {
aoqi@0:     if (block->chain_contains(handle)) {
aoqi@0:       return true;
aoqi@0:     }
aoqi@0:     block = block->pop_frame_link();
aoqi@0:   }
aoqi@0:   return false;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // Determine if the handle is somewhere in the current thread's stack.
aoqi@0: // We easily can't isolate any particular stack frame the handle might
aoqi@0: // come from, so we'll check the whole stack.
aoqi@0: 
aoqi@0: bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) {
aoqi@0:   // If there is no java frame, then this must be top level code, such
aoqi@0:   // as the java command executable, in which case, this type of handle
aoqi@0:   // is not permitted.
aoqi@0:   return (thr->has_last_Java_frame() &&
aoqi@0:          (void*)obj < (void*)thr->stack_base() &&
aoqi@0:          (void*)obj >= (void*)thr->last_Java_sp());
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: bool JNIHandles::is_global_handle(jobject handle) {
aoqi@0:   return _global_handles->chain_contains(handle);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: bool JNIHandles::is_weak_global_handle(jobject handle) {
aoqi@0:   return _weak_global_handles->chain_contains(handle);
aoqi@0: }
aoqi@0: 
aoqi@0: long JNIHandles::global_handle_memory_usage() {
aoqi@0:   return _global_handles->memory_usage();
aoqi@0: }
aoqi@0: 
aoqi@0: long JNIHandles::weak_global_handle_memory_usage() {
aoqi@0:   return _weak_global_handles->memory_usage();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: class AlwaysAliveClosure: public BoolObjectClosure {
aoqi@0: public:
aoqi@0:   bool do_object_b(oop obj) { return true; }
aoqi@0: };
aoqi@0: 
aoqi@0: class CountHandleClosure: public OopClosure {
aoqi@0: private:
aoqi@0:   int _count;
aoqi@0: public:
aoqi@0:   CountHandleClosure(): _count(0) {}
aoqi@0:   virtual void do_oop(oop* unused) {
aoqi@0:     _count++;
aoqi@0:   }
aoqi@0:   virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
aoqi@0:   int count() { return _count; }
aoqi@0: };
aoqi@0: 
aoqi@0: // We assume this is called at a safepoint: no lock is needed.
aoqi@0: void JNIHandles::print_on(outputStream* st) {
aoqi@0:   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
aoqi@0:   assert(_global_handles != NULL && _weak_global_handles != NULL,
aoqi@0:          "JNIHandles not initialized");
aoqi@0: 
aoqi@0:   CountHandleClosure global_handle_count;
aoqi@0:   AlwaysAliveClosure always_alive;
aoqi@0:   oops_do(&global_handle_count);
aoqi@0:   weak_oops_do(&always_alive, &global_handle_count);
aoqi@0: 
aoqi@0:   st->print_cr("JNI global references: %d", global_handle_count.count());
aoqi@0:   st->cr();
aoqi@0:   st->flush();
aoqi@0: }
aoqi@0: 
aoqi@0: class VerifyHandleClosure: public OopClosure {
aoqi@0: public:
aoqi@0:   virtual void do_oop(oop* root) {
aoqi@0:     (*root)->verify();
aoqi@0:   }
aoqi@0:   virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
aoqi@0: };
aoqi@0: 
aoqi@0: void JNIHandles::verify() {
aoqi@0:   VerifyHandleClosure verify_handle;
aoqi@0:   AlwaysAliveClosure always_alive;
aoqi@0: 
aoqi@0:   oops_do(&verify_handle);
aoqi@0:   weak_oops_do(&always_alive, &verify_handle);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: 
aoqi@0: void jni_handles_init() {
aoqi@0:   JNIHandles::initialize();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: int             JNIHandleBlock::_blocks_allocated     = 0;
aoqi@0: JNIHandleBlock* JNIHandleBlock::_block_free_list      = NULL;
aoqi@0: #ifndef PRODUCT
aoqi@0: JNIHandleBlock* JNIHandleBlock::_block_list           = NULL;
aoqi@0: #endif
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandleBlock::zap() {
aoqi@0:   // Zap block values
aoqi@0:   _top  = 0;
aoqi@0:   for (int index = 0; index < block_size_in_oops; index++) {
aoqi@0:     _handles[index] = badJNIHandle;
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread)  {
aoqi@0:   assert(thread == NULL || thread == Thread::current(), "sanity check");
aoqi@0:   JNIHandleBlock* block;
aoqi@0:   // Check the thread-local free list for a block so we don't
aoqi@0:   // have to acquire a mutex.
aoqi@0:   if (thread != NULL && thread->free_handle_block() != NULL) {
aoqi@0:     block = thread->free_handle_block();
aoqi@0:     thread->set_free_handle_block(block->_next);
aoqi@0:   }
aoqi@0:   else {
aoqi@0:     // locking with safepoint checking introduces a potential deadlock:
aoqi@0:     // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
aoqi@0:     // - another would hold Threads_lock (jni_AttachCurrentThread) and then
aoqi@0:     //   JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
aoqi@0:     MutexLockerEx ml(JNIHandleBlockFreeList_lock,
aoqi@0:                      Mutex::_no_safepoint_check_flag);
aoqi@0:     if (_block_free_list == NULL) {
aoqi@0:       // Allocate new block
aoqi@0:       block = new JNIHandleBlock();
aoqi@0:       _blocks_allocated++;
aoqi@0:       if (TraceJNIHandleAllocation) {
aoqi@0:         tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)",
aoqi@0:                       block, _blocks_allocated);
aoqi@0:       }
aoqi@0:       if (ZapJNIHandleArea) block->zap();
aoqi@0:       #ifndef PRODUCT
aoqi@0:       // Link new block to list of all allocated blocks
aoqi@0:       block->_block_list_link = _block_list;
aoqi@0:       _block_list = block;
aoqi@0:       #endif
aoqi@0:     } else {
aoqi@0:       // Get block from free list
aoqi@0:       block = _block_free_list;
aoqi@0:       _block_free_list = _block_free_list->_next;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   block->_top  = 0;
aoqi@0:   block->_next = NULL;
aoqi@0:   block->_pop_frame_link = NULL;
poonam@7627:   block->_planned_capacity = block_size_in_oops;
aoqi@0:   // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
aoqi@0:   debug_only(block->_last = NULL);
aoqi@0:   debug_only(block->_free_list = NULL);
aoqi@0:   debug_only(block->_allocate_before_rebuild = -1);
aoqi@0:   return block;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
aoqi@0:   assert(thread == NULL || thread == Thread::current(), "sanity check");
aoqi@0:   JNIHandleBlock* pop_frame_link = block->pop_frame_link();
aoqi@0:   // Put returned block at the beginning of the thread-local free list.
aoqi@0:   // Note that if thread == NULL, we use it as an implicit argument that
aoqi@0:   // we _don't_ want the block to be kept on the free_handle_block.
aoqi@0:   // See for instance JavaThread::exit().
aoqi@0:   if (thread != NULL ) {
aoqi@0:     if (ZapJNIHandleArea) block->zap();
aoqi@0:     JNIHandleBlock* freelist = thread->free_handle_block();
aoqi@0:     block->_pop_frame_link = NULL;
aoqi@0:     thread->set_free_handle_block(block);
aoqi@0: 
aoqi@0:     // Add original freelist to end of chain
aoqi@0:     if ( freelist != NULL ) {
aoqi@0:       while ( block->_next != NULL ) block = block->_next;
aoqi@0:       block->_next = freelist;
aoqi@0:     }
aoqi@0:     block = NULL;
aoqi@0:   }
aoqi@0:   if (block != NULL) {
aoqi@0:     // Return blocks to free list
aoqi@0:     // locking with safepoint checking introduces a potential deadlock:
aoqi@0:     // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
aoqi@0:     // - another would hold Threads_lock (jni_AttachCurrentThread) and then
aoqi@0:     //   JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
aoqi@0:     MutexLockerEx ml(JNIHandleBlockFreeList_lock,
aoqi@0:                      Mutex::_no_safepoint_check_flag);
aoqi@0:     while (block != NULL) {
aoqi@0:       if (ZapJNIHandleArea) block->zap();
aoqi@0:       JNIHandleBlock* next = block->_next;
aoqi@0:       block->_next = _block_free_list;
aoqi@0:       _block_free_list = block;
aoqi@0:       block = next;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   if (pop_frame_link != NULL) {
aoqi@0:     // As a sanity check we release blocks pointed to by the pop_frame_link.
aoqi@0:     // This should never happen (only if PopLocalFrame is not called the
aoqi@0:     // correct number of times).
aoqi@0:     release_block(pop_frame_link, thread);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandleBlock::oops_do(OopClosure* f) {
aoqi@0:   JNIHandleBlock* current_chain = this;
aoqi@0:   // Iterate over chain of blocks, followed by chains linked through the
aoqi@0:   // pop frame links.
aoqi@0:   while (current_chain != NULL) {
aoqi@0:     for (JNIHandleBlock* current = current_chain; current != NULL;
aoqi@0:          current = current->_next) {
aoqi@0:       assert(current == current_chain || current->pop_frame_link() == NULL,
aoqi@0:         "only blocks first in chain should have pop frame link set");
aoqi@0:       for (int index = 0; index < current->_top; index++) {
aoqi@0:         oop* root = &(current->_handles)[index];
aoqi@0:         oop value = *root;
aoqi@0:         // traverse heap pointers only, not deleted handles or free list
aoqi@0:         // pointers
aoqi@0:         if (value != NULL && Universe::heap()->is_in_reserved(value)) {
aoqi@0:           f->do_oop(root);
aoqi@0:         }
aoqi@0:       }
aoqi@0:       // the next handle block is valid only if current block is full
aoqi@0:       if (current->_top < block_size_in_oops) {
aoqi@0:         break;
aoqi@0:       }
aoqi@0:     }
aoqi@0:     current_chain = current_chain->pop_frame_link();
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive,
aoqi@0:                                   OopClosure* f) {
aoqi@0:   for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
aoqi@0:     assert(current->pop_frame_link() == NULL,
aoqi@0:       "blocks holding weak global JNI handles should not have pop frame link set");
aoqi@0:     for (int index = 0; index < current->_top; index++) {
aoqi@0:       oop* root = &(current->_handles)[index];
aoqi@0:       oop value = *root;
aoqi@0:       // traverse heap pointers only, not deleted handles or free list pointers
aoqi@0:       if (value != NULL && Universe::heap()->is_in_reserved(value)) {
aoqi@0:         if (is_alive->do_object_b(value)) {
aoqi@0:           // The weakly referenced object is alive, update pointer
aoqi@0:           f->do_oop(root);
aoqi@0:         } else {
aoqi@0:           // The weakly referenced object is not alive, clear the reference by storing NULL
aoqi@0:           if (TraceReferenceGC) {
aoqi@0:             tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root);
aoqi@0:           }
aoqi@0:           *root = NULL;
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:     // the next handle block is valid only if current block is full
aoqi@0:     if (current->_top < block_size_in_oops) {
aoqi@0:       break;
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   /*
aoqi@0:    * JVMTI data structures may also contain weak oops.  The iteration of them
aoqi@0:    * is placed here so that we don't need to add it to each of the collectors.
aoqi@0:    */
aoqi@0:   JvmtiExport::weak_oops_do(is_alive, f);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: jobject JNIHandleBlock::allocate_handle(oop obj) {
aoqi@0:   assert(Universe::heap()->is_in_reserved(obj), "sanity check");
aoqi@0:   if (_top == 0) {
aoqi@0:     // This is the first allocation or the initial block got zapped when
aoqi@0:     // entering a native function. If we have any following blocks they are
aoqi@0:     // not valid anymore.
aoqi@0:     for (JNIHandleBlock* current = _next; current != NULL;
aoqi@0:          current = current->_next) {
aoqi@0:       assert(current->_last == NULL, "only first block should have _last set");
aoqi@0:       assert(current->_free_list == NULL,
aoqi@0:              "only first block should have _free_list set");
aoqi@0:       current->_top = 0;
aoqi@0:       if (ZapJNIHandleArea) current->zap();
aoqi@0:     }
aoqi@0:     // Clear initial block
aoqi@0:     _free_list = NULL;
aoqi@0:     _allocate_before_rebuild = 0;
aoqi@0:     _last = this;
aoqi@0:     if (ZapJNIHandleArea) zap();
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Try last block
aoqi@0:   if (_last->_top < block_size_in_oops) {
aoqi@0:     oop* handle = &(_last->_handles)[_last->_top++];
aoqi@0:     *handle = obj;
aoqi@0:     return (jobject) handle;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Try free list
aoqi@0:   if (_free_list != NULL) {
aoqi@0:     oop* handle = _free_list;
aoqi@0:     _free_list = (oop*) *_free_list;
aoqi@0:     *handle = obj;
aoqi@0:     return (jobject) handle;
aoqi@0:   }
aoqi@0:   // Check if unused block follow last
aoqi@0:   if (_last->_next != NULL) {
aoqi@0:     // update last and retry
aoqi@0:     _last = _last->_next;
aoqi@0:     return allocate_handle(obj);
aoqi@0:   }
aoqi@0: 
aoqi@0:   // No space available, we have to rebuild free list or expand
aoqi@0:   if (_allocate_before_rebuild == 0) {
aoqi@0:       rebuild_free_list();        // updates _allocate_before_rebuild counter
aoqi@0:   } else {
aoqi@0:     // Append new block
aoqi@0:     Thread* thread = Thread::current();
aoqi@0:     Handle obj_handle(thread, obj);
aoqi@0:     // This can block, so we need to preserve obj accross call.
aoqi@0:     _last->_next = JNIHandleBlock::allocate_block(thread);
aoqi@0:     _last = _last->_next;
aoqi@0:     _allocate_before_rebuild--;
aoqi@0:     obj = obj_handle();
aoqi@0:   }
aoqi@0:   return allocate_handle(obj);  // retry
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void JNIHandleBlock::rebuild_free_list() {
aoqi@0:   assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
aoqi@0:   int free = 0;
aoqi@0:   int blocks = 0;
aoqi@0:   for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
aoqi@0:     for (int index = 0; index < current->_top; index++) {
aoqi@0:       oop* handle = &(current->_handles)[index];
aoqi@0:       if (*handle ==  JNIHandles::deleted_handle()) {
aoqi@0:         // this handle was cleared out by a delete call, reuse it
aoqi@0:         *handle = (oop) _free_list;
aoqi@0:         _free_list = handle;
aoqi@0:         free++;
aoqi@0:       }
aoqi@0:     }
aoqi@0:     // we should not rebuild free list if there are unused handles at the end
aoqi@0:     assert(current->_top == block_size_in_oops, "just checking");
aoqi@0:     blocks++;
aoqi@0:   }
aoqi@0:   // Heuristic: if more than half of the handles are free we rebuild next time
aoqi@0:   // as well, otherwise we append a corresponding number of new blocks before
aoqi@0:   // attempting a free list rebuild again.
aoqi@0:   int total = blocks * block_size_in_oops;
aoqi@0:   int extra = total - 2*free;
aoqi@0:   if (extra > 0) {
aoqi@0:     // Not as many free handles as we would like - compute number of new blocks to append
aoqi@0:     _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
aoqi@0:   }
aoqi@0:   if (TraceJNIHandleAllocation) {
aoqi@0:     tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d",
aoqi@0:       this, blocks, total-free, free, _allocate_before_rebuild);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: bool JNIHandleBlock::contains(jobject handle) const {
aoqi@0:   return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: bool JNIHandleBlock::chain_contains(jobject handle) const {
aoqi@0:   for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
aoqi@0:     if (current->contains(handle)) {
aoqi@0:       return true;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   return false;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: int JNIHandleBlock::length() const {
aoqi@0:   int result = 1;
aoqi@0:   for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
aoqi@0:     result++;
aoqi@0:   }
aoqi@0:   return result;
aoqi@0: }
aoqi@0: 
poonam@7627: const size_t JNIHandleBlock::get_number_of_live_handles() {
poonam@7627:   CountHandleClosure counter;
poonam@7627:   oops_do(&counter);
poonam@7627:   return counter.count();
poonam@7627: }
poonam@7627: 
aoqi@0: // This method is not thread-safe, i.e., must be called whule holding a lock on the
aoqi@0: // structure.
aoqi@0: long JNIHandleBlock::memory_usage() const {
aoqi@0:   return length() * sizeof(JNIHandleBlock);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: #ifndef PRODUCT
aoqi@0: 
aoqi@0: bool JNIHandleBlock::any_contains(jobject handle) {
aoqi@0:   for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
aoqi@0:     if (current->contains(handle)) {
aoqi@0:       return true;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   return false;
aoqi@0: }
aoqi@0: 
aoqi@0: void JNIHandleBlock::print_statistics() {
aoqi@0:   int used_blocks = 0;
aoqi@0:   int free_blocks = 0;
aoqi@0:   int used_handles = 0;
aoqi@0:   int free_handles = 0;
aoqi@0:   JNIHandleBlock* block = _block_list;
aoqi@0:   while (block != NULL) {
aoqi@0:     if (block->_top > 0) {
aoqi@0:       used_blocks++;
aoqi@0:     } else {
aoqi@0:       free_blocks++;
aoqi@0:     }
aoqi@0:     used_handles += block->_top;
aoqi@0:     free_handles += (block_size_in_oops - block->_top);
aoqi@0:     block = block->_block_list_link;
aoqi@0:   }
aoqi@0:   tty->print_cr("JNIHandleBlocks statistics");
aoqi@0:   tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
aoqi@0:   tty->print_cr("- blocks in use:    %d", used_blocks);
aoqi@0:   tty->print_cr("- blocks free:      %d", free_blocks);
aoqi@0:   tty->print_cr("- handles in use:   %d", used_handles);
aoqi@0:   tty->print_cr("- handles free:     %d", free_handles);
aoqi@0: }
aoqi@0: 
aoqi@0: #endif