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src/share/vm/runtime/jniHandles.hpp@0715f0cf171d (annotated)

src/share/vm/runtime/jniHandles.hpp

Fri, 08 Oct 2010 09:29:09 -0700

author

jcoomes

date

Fri, 08 Oct 2010 09:29:09 -0700

changeset 2198

0715f0cf171d

parent 1907

c18cbe5936b8

child 2314

f95d63e2154a

permissions

-rw-r--r--

Merge

duke@435	1	/*
trims@1907	2	* Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
trims@1907	19	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907	20	* or visit www.oracle.com if you need additional information or have any
trims@1907	21	* questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	class JNIHandleBlock;
duke@435	26
duke@435	27
duke@435	28	// Interface for creating and resolving local/global JNI handles
duke@435	29
duke@435	30	class JNIHandles : AllStatic {
duke@435	31	friend class VMStructs;
duke@435	32	private:
duke@435	33	static JNIHandleBlock* _global_handles; // First global handle block
duke@435	34	static JNIHandleBlock* _weak_global_handles; // First weak global handle block
duke@435	35	static oop _deleted_handle; // Sentinel marking deleted handles
duke@435	36
duke@435	37	public:
duke@435	38	// Resolve handle into oop
duke@435	39	inline static oop resolve(jobject handle);
duke@435	40	// Resolve externally provided handle into oop with some guards
duke@435	41	inline static oop resolve_external_guard(jobject handle);
duke@435	42	// Resolve handle into oop, result guaranteed not to be null
duke@435	43	inline static oop resolve_non_null(jobject handle);
duke@435	44
duke@435	45	// Local handles
duke@435	46	static jobject make_local(oop obj);
duke@435	47	static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known
duke@435	48	static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known
duke@435	49	inline static void destroy_local(jobject handle);
duke@435	50
duke@435	51	// Global handles
duke@435	52	static jobject make_global(Handle obj);
duke@435	53	static void destroy_global(jobject handle);
duke@435	54
duke@435	55	// Weak global handles
duke@435	56	static jobject make_weak_global(Handle obj);
duke@435	57	static void destroy_weak_global(jobject handle);
duke@435	58
duke@435	59	// jmethodID handling (as Weak global handles).
duke@435	60	// Because the useful life-span of a jmethodID cannot be determined, once created they are
duke@435	61	// never reclaimed. The methods to which they refer, however, can be GC'ed away if the class
duke@435	62	// is unloaded or if the method is made obsolete or deleted -- in these cases, the jmethodID
duke@435	63	// refers to NULL (as is the case for any weak reference).
duke@435	64	static jmethodID make_jmethod_id(methodHandle mh);
duke@435	65	static void destroy_jmethod_id(jmethodID mid);
dcubed@1890	66	// Use resolve_jmethod_id() in situations where the caller is expected
dcubed@1890	67	// to provide a valid jmethodID; the only sanity checks are in asserts;
dcubed@1890	68	// result guaranteed not to be NULL.
duke@435	69	inline static methodOop resolve_jmethod_id(jmethodID mid);
dcubed@1890	70	// Use checked_resolve_jmethod_id() in situations where the caller
dcubed@1890	71	// should provide a valid jmethodID, but might not. NULL is returned
dcubed@1890	72	// when the jmethodID does not refer to a valid method.
dcubed@1890	73	inline static methodOop checked_resolve_jmethod_id(jmethodID mid);
duke@435	74	static void change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh);
duke@435	75
duke@435	76	// Sentinel marking deleted handles in block. Note that we cannot store NULL as
duke@435	77	// the sentinel, since clearing weak global JNI refs are done by storing NULL in
duke@435	78	// the handle. The handle may not be reused before destroy_weak_global is called.
duke@435	79	static oop deleted_handle() { return _deleted_handle; }
duke@435	80
duke@435	81	// Initialization
duke@435	82	static void initialize();
duke@435	83
duke@435	84	// Debugging
duke@435	85	static void print_on(outputStream* st);
duke@435	86	static void print() { print_on(tty); }
duke@435	87	static void verify();
duke@435	88	static bool is_local_handle(Thread* thread, jobject handle);
duke@435	89	static bool is_frame_handle(JavaThread* thr, jobject obj);
duke@435	90	static bool is_global_handle(jobject handle);
duke@435	91	static bool is_weak_global_handle(jobject handle);
duke@435	92	static long global_handle_memory_usage();
duke@435	93	static long weak_global_handle_memory_usage();
duke@435	94
duke@435	95	// Garbage collection support(global handles only, local handles are traversed from thread)
duke@435	96	// Traversal of regular global handles
duke@435	97	static void oops_do(OopClosure* f);
duke@435	98	// Traversal of weak global handles. Unreachable oops are cleared.
duke@435	99	static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
duke@435	100	};
duke@435	101
duke@435	102
duke@435	103
duke@435	104	// JNI handle blocks holding local/global JNI handles
duke@435	105
duke@435	106	class JNIHandleBlock : public CHeapObj {
duke@435	107	friend class VMStructs;
never@1445	108	friend class CppInterpreter;
never@1445	109
duke@435	110	private:
duke@435	111	enum SomeConstants {
duke@435	112	block_size_in_oops = 32 // Number of handles per handle block
duke@435	113	};
duke@435	114
duke@435	115	oop _handles[block_size_in_oops]; // The handles
duke@435	116	int _top; // Index of next unused handle
duke@435	117	JNIHandleBlock* _next; // Link to next block
duke@435	118
duke@435	119	// The following instance variables are only used by the first block in a chain.
duke@435	120	// Having two types of blocks complicates the code and the space overhead in negligble.
duke@435	121	JNIHandleBlock* _last; // Last block in use
duke@435	122	JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call
duke@435	123	oop* _free_list; // Handle free list
duke@435	124	int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list
duke@435	125
duke@435	126	#ifndef PRODUCT
duke@435	127	JNIHandleBlock* _block_list_link; // Link for list below
duke@435	128	static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only)
duke@435	129	#endif
duke@435	130
duke@435	131	static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks
duke@435	132	static int _blocks_allocated; // For debugging/printing
duke@435	133
duke@435	134	// Fill block with bad_handle values
duke@435	135	void zap();
duke@435	136
never@1445	137	protected:
duke@435	138	// No more handles in the both the current and following blocks
duke@435	139	void clear() { _top = 0; }
duke@435	140
never@1445	141	private:
duke@435	142	// Free list computation
duke@435	143	void rebuild_free_list();
duke@435	144
duke@435	145	public:
duke@435	146	// Handle allocation
duke@435	147	jobject allocate_handle(oop obj);
duke@435	148
duke@435	149	// Block allocation and block free list management
duke@435	150	static JNIHandleBlock* allocate_block(Thread* thread = NULL);
duke@435	151	static void release_block(JNIHandleBlock* block, Thread* thread = NULL);
duke@435	152
duke@435	153	// JNI PushLocalFrame/PopLocalFrame support
duke@435	154	JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; }
duke@435	155	void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; }
duke@435	156
duke@435	157	// Stub generator support
duke@435	158	static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); }
duke@435	159
duke@435	160	// Garbage collection support
duke@435	161	// Traversal of regular handles
duke@435	162	void oops_do(OopClosure* f);
duke@435	163	// Traversal of weak handles. Unreachable oops are cleared.
duke@435	164	void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
duke@435	165
duke@435	166	// Debugging
duke@435	167	bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle
duke@435	168	bool contains(jobject handle) const; // Does this block contain handle
duke@435	169	int length() const; // Length of chain starting with this block
duke@435	170	long memory_usage() const;
duke@435	171	#ifndef PRODUCT
duke@435	172	static bool any_contains(jobject handle); // Does any block currently in use contain handle
duke@435	173	static void print_statistics();
duke@435	174	#endif
duke@435	175	};
duke@435	176
duke@435	177
duke@435	178	inline oop JNIHandles::resolve(jobject handle) {
duke@435	179	oop result = (handle == NULL ? (oop)NULL : *(oop*)handle);
duke@435	180	assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle");
duke@435	181	assert(result != badJNIHandle, "Pointing to zapped jni handle area");
duke@435	182	return result;
duke@435	183	};
duke@435	184
duke@435	185
duke@435	186	inline oop JNIHandles::resolve_external_guard(jobject handle) {
duke@435	187	if (handle == NULL) return NULL;
duke@435	188	oop result = *(oop*)handle;
duke@435	189	if (result == NULL || result == badJNIHandle) return NULL;
duke@435	190	return result;
duke@435	191	};
duke@435	192
duke@435	193
duke@435	194	inline oop JNIHandles::resolve_non_null(jobject handle) {
duke@435	195	assert(handle != NULL, "JNI handle should not be null");
duke@435	196	oop result = *(oop*)handle;
duke@435	197	assert(result != NULL, "Invalid value read from jni handle");
duke@435	198	assert(result != badJNIHandle, "Pointing to zapped jni handle area");
duke@435	199	// Don't let that private _deleted_handle object escape into the wild.
duke@435	200	assert(result != deleted_handle(), "Used a deleted global handle.");
duke@435	201	return result;
duke@435	202	};
duke@435	203
duke@435	204	inline methodOop JNIHandles::resolve_jmethod_id(jmethodID mid) {
duke@435	205	return (methodOop) resolve_non_null((jobject)mid);
duke@435	206	};
duke@435	207
duke@435	208	inline methodOop JNIHandles::checked_resolve_jmethod_id(jmethodID mid) {
dcubed@1890	209	oop o = resolve_external_guard((jobject) mid);
dcubed@1890	210	if (o == NULL || !o->is_method()) {
dcubed@1352	211	return (methodOop) NULL;
dcubed@1352	212	}
dcubed@1352	213
dcubed@1352	214	return (methodOop) o;
duke@435	215	};
duke@435	216
duke@435	217
duke@435	218	inline void JNIHandles::destroy_local(jobject handle) {
duke@435	219	if (handle != NULL) {
duke@435	220	*((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
duke@435	221	}
duke@435	222	}