diff -r 000000000000 -r f90c822e73f8 src/share/vm/runtime/jniHandles.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/runtime/jniHandles.hpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,199 @@ +/* + * Copyright (c) 1998, 2012, 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. + * + */ + +#ifndef SHARE_VM_RUNTIME_JNIHANDLES_HPP +#define SHARE_VM_RUNTIME_JNIHANDLES_HPP + +#include "runtime/handles.hpp" +#include "utilities/top.hpp" + +class JNIHandleBlock; + + +// Interface for creating and resolving local/global JNI handles + +class JNIHandles : AllStatic { + friend class VMStructs; + private: + static JNIHandleBlock* _global_handles; // First global handle block + static JNIHandleBlock* _weak_global_handles; // First weak global handle block + static oop _deleted_handle; // Sentinel marking deleted handles + + public: + // Resolve handle into oop + inline static oop resolve(jobject handle); + // Resolve externally provided handle into oop with some guards + inline static oop resolve_external_guard(jobject handle); + // Resolve handle into oop, result guaranteed not to be null + inline static oop resolve_non_null(jobject handle); + + // Local handles + static jobject make_local(oop obj); + static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known + static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known + inline static void destroy_local(jobject handle); + + // Global handles + static jobject make_global(Handle obj); + static void destroy_global(jobject handle); + + // Weak global handles + static jobject make_weak_global(Handle obj); + static void destroy_weak_global(jobject handle); + + // Sentinel marking deleted handles in block. Note that we cannot store NULL as + // the sentinel, since clearing weak global JNI refs are done by storing NULL in + // the handle. The handle may not be reused before destroy_weak_global is called. + static oop deleted_handle() { return _deleted_handle; } + + // Initialization + static void initialize(); + + // Debugging + static void print_on(outputStream* st); + static void print() { print_on(tty); } + static void verify(); + static bool is_local_handle(Thread* thread, jobject handle); + static bool is_frame_handle(JavaThread* thr, jobject obj); + static bool is_global_handle(jobject handle); + static bool is_weak_global_handle(jobject handle); + static long global_handle_memory_usage(); + static long weak_global_handle_memory_usage(); + + // Garbage collection support(global handles only, local handles are traversed from thread) + // Traversal of regular global handles + static void oops_do(OopClosure* f); + // Traversal of weak global handles. Unreachable oops are cleared. + static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f); +}; + + + +// JNI handle blocks holding local/global JNI handles + +class JNIHandleBlock : public CHeapObj { + friend class VMStructs; + friend class CppInterpreter; + + private: + enum SomeConstants { + block_size_in_oops = 32 // Number of handles per handle block + }; + + oop _handles[block_size_in_oops]; // The handles + int _top; // Index of next unused handle + JNIHandleBlock* _next; // Link to next block + + // The following instance variables are only used by the first block in a chain. + // Having two types of blocks complicates the code and the space overhead in negligble. + JNIHandleBlock* _last; // Last block in use + JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call + oop* _free_list; // Handle free list + int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list + + #ifndef PRODUCT + JNIHandleBlock* _block_list_link; // Link for list below + static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only) + #endif + + static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks + static int _blocks_allocated; // For debugging/printing + + // Fill block with bad_handle values + void zap(); + + protected: + // No more handles in the both the current and following blocks + void clear() { _top = 0; } + + private: + // Free list computation + void rebuild_free_list(); + + public: + // Handle allocation + jobject allocate_handle(oop obj); + + // Block allocation and block free list management + static JNIHandleBlock* allocate_block(Thread* thread = NULL); + static void release_block(JNIHandleBlock* block, Thread* thread = NULL); + + // JNI PushLocalFrame/PopLocalFrame support + JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; } + void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; } + + // Stub generator support + static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); } + + // Garbage collection support + // Traversal of regular handles + void oops_do(OopClosure* f); + // Traversal of weak handles. Unreachable oops are cleared. + void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f); + + // Debugging + bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle + bool contains(jobject handle) const; // Does this block contain handle + int length() const; // Length of chain starting with this block + long memory_usage() const; + #ifndef PRODUCT + static bool any_contains(jobject handle); // Does any block currently in use contain handle + static void print_statistics(); + #endif +}; + + +inline oop JNIHandles::resolve(jobject handle) { + oop result = (handle == NULL ? (oop)NULL : *(oop*)handle); + assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle"); + assert(result != badJNIHandle, "Pointing to zapped jni handle area"); + return result; +}; + + +inline oop JNIHandles::resolve_external_guard(jobject handle) { + if (handle == NULL) return NULL; + oop result = *(oop*)handle; + if (result == NULL || result == badJNIHandle) return NULL; + return result; +}; + + +inline oop JNIHandles::resolve_non_null(jobject handle) { + assert(handle != NULL, "JNI handle should not be null"); + oop result = *(oop*)handle; + assert(result != NULL, "Invalid value read from jni handle"); + assert(result != badJNIHandle, "Pointing to zapped jni handle area"); + // Don't let that private _deleted_handle object escape into the wild. + assert(result != deleted_handle(), "Used a deleted global handle."); + return result; +}; + +inline void JNIHandles::destroy_local(jobject handle) { + if (handle != NULL) { + *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it + } +} + +#endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP