/*

 * Copyright (c) 1998, 2014, 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 "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::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 AlwaysAliveClosure: public BoolObjectClosure {

public:

  bool do_object_b(oop obj) { return true; }

};

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;

  AlwaysAliveClosure always_alive;

  oops_do(&global_handle_count);

  weak_oops_do(&always_alive, &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;

  AlwaysAliveClosure always_alive;

  oops_do(&verify_handle);

  weak_oops_do(&always_alive, &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 (TraceJNIHandleAllocation) {

        tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)",

                      p2i(block), _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

          if (TraceReferenceGC) {

            tty->print_cr("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::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;

  }

  if (TraceJNIHandleAllocation) {

    tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d",

                  p2i(this), blocks, total-free, free, _allocate_before_rebuild);

  }

}

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;

}