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view src/share/vm/runtime/jniHandles.hpp @ 3979:4dfb2df418f2
6484982: G1: process references during evacuation pauses
Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp
author | johnc |
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date | Thu, 22 Sep 2011 10:57:37 -0700 |
parents | f95d63e2154a |
children | d2a62e0f25eb |
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/* * Copyright (c) 1998, 2010, 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); // jmethodID handling (as Weak global handles). // Because the useful life-span of a jmethodID cannot be determined, once created they are // never reclaimed. The methods to which they refer, however, can be GC'ed away if the class // is unloaded or if the method is made obsolete or deleted -- in these cases, the jmethodID // refers to NULL (as is the case for any weak reference). static jmethodID make_jmethod_id(methodHandle mh); static void destroy_jmethod_id(jmethodID mid); // Use resolve_jmethod_id() in situations where the caller is expected // to provide a valid jmethodID; the only sanity checks are in asserts; // result guaranteed not to be NULL. inline static methodOop resolve_jmethod_id(jmethodID mid); // Use checked_resolve_jmethod_id() in situations where the caller // should provide a valid jmethodID, but might not. NULL is returned // when the jmethodID does not refer to a valid method. inline static methodOop checked_resolve_jmethod_id(jmethodID mid); static void change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh); // 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 methodOop JNIHandles::resolve_jmethod_id(jmethodID mid) { return (methodOop) resolve_non_null((jobject)mid); }; inline methodOop JNIHandles::checked_resolve_jmethod_id(jmethodID mid) { oop o = resolve_external_guard((jobject) mid); if (o == NULL || !o->is_method()) { return (methodOop) NULL; } return (methodOop) o; }; 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