Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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"

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 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* unused) {

     _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)",

                       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;

   // _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 ")", 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 accross 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",

       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;

 }

 int JNIHandleBlock::length() const {

   int result = 1;

   for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {

     result++;

   }

   return result;

 }

 // This method is not thread-safe, i.e., must be called whule 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