1 /*
2 * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "jfr/recorder/storage/jfrBuffer.hpp"
27 #include "runtime/atomic.inline.hpp"
28 #include "runtime/orderAccess.inline.hpp"
29 #include "runtime/thread.inline.hpp"
30 #include "jfr/recorder/jfrRecorder.hpp"
31
32 static const u1* const MUTEX_CLAIM = NULL;
33
34 JfrBuffer::JfrBuffer() : _next(NULL),
35 _prev(NULL),
36 _identity(NULL),
37 _pos(NULL),
38 _top(NULL),
39 _flags(0),
40 _header_size(0),
41 _size(0) {}
42
43 bool JfrBuffer::initialize(size_t header_size, size_t size, const void* id /* NULL */) {
44 _header_size = (u2)header_size;
45 _size = (u4)(size / BytesPerWord);
46 assert(_identity == NULL, "invariant");
47 _identity = id;
48 set_pos(start());
49 set_top(start());
50 assert(_next == NULL, "invariant");
51 assert(free_size() == size, "invariant");
52 assert(!transient(), "invariant");
53 assert(!lease(), "invariant");
54 assert(!retired(), "invariant");
55 return true;
56 }
57
58 void JfrBuffer::reinitialize() {
59 assert(!lease(), "invariant");
60 assert(!transient(), "invariant");
61 set_pos(start());
62 clear_retired();
63 set_top(start());
64 }
65
66 void JfrBuffer::concurrent_reinitialization() {
67 concurrent_top();
68 assert(!lease(), "invariant");
69 assert(!transient(), "invariant");
70 set_pos(start());
71 set_concurrent_top(start());
72 clear_retired();
73 }
74
75 size_t JfrBuffer::discard() {
76 size_t discard_size = unflushed_size();
77 set_top(pos());
78 return discard_size;
79 }
80
81 const u1* JfrBuffer::stable_top() const {
82 const u1* current_top;
83 do {
84 current_top = (const u1*)OrderAccess::load_ptr_acquire(&_top);
85 } while (MUTEX_CLAIM == current_top);
86 return current_top;
87 }
88
89 const u1* JfrBuffer::top() const {
90 return _top;
91 }
92
93 void JfrBuffer::set_top(const u1* new_top) {
94 _top = new_top;
95 }
96
97 const u1* JfrBuffer::concurrent_top() const {
98 do {
99 const u1* current_top = stable_top();
100 if (Atomic::cmpxchg_ptr((void*)MUTEX_CLAIM, &_top, (void*)current_top) == current_top) {
101 return current_top;
102 }
103 } while (true);
104 }
105
106 void JfrBuffer::set_concurrent_top(const u1* new_top) {
107 assert(new_top != MUTEX_CLAIM, "invariant");
108 assert(new_top <= end(), "invariant");
109 assert(new_top >= start(), "invariant");
110 assert(top() == MUTEX_CLAIM, "invariant");
111 OrderAccess::release_store_ptr(&_top, (void*)new_top);
112 }
113
114 size_t JfrBuffer::unflushed_size() const {
115 return pos() - stable_top();
116 }
117
118 void JfrBuffer::acquire(const void* id) {
119 assert(id != NULL, "invariant");
120 const void* current_id;
121 do {
122 current_id = OrderAccess::load_ptr_acquire(&_identity);
123 } while (current_id != NULL || Atomic::cmpxchg_ptr((void*)id, &_identity, (void*)current_id) != current_id);
124 }
125
126 bool JfrBuffer::try_acquire(const void* id) {
127 assert(id != NULL, "invariant");
128 const void* const current_id = OrderAccess::load_ptr_acquire(&_identity);
129 return current_id == NULL && Atomic::cmpxchg_ptr((void*)id, &_identity, (void*)current_id) == current_id;
130 }
131
132 void JfrBuffer::release() {
133 OrderAccess::release_store_ptr(&_identity, (void*)NULL);
134 }
135
136 void JfrBuffer::clear_identity() {
137 _identity = NULL;
138 }
139
140 #ifdef ASSERT
141 static bool validate_to(const JfrBuffer* const to, size_t size) {
142 assert(to != NULL, "invariant");
143 if (!JfrRecorder::is_shutting_down()) assert(to->acquired_by_self(), "invariant");
144 assert(to->free_size() >= size, "invariant");
145 return true;
146 }
147
148 static bool validate_concurrent_this(const JfrBuffer* const t, size_t size) {
149 assert(t->top() == MUTEX_CLAIM, "invariant");
150 return true;
151 }
152
153 static bool validate_this(const JfrBuffer* const t, size_t size) {
154 assert(t->top() + size <= t->pos(), "invariant");
155 return true;
156 }
157
158 bool JfrBuffer::acquired_by_self() const {
159 return identity() == Thread::current();
160 }
161 #endif // ASSERT
162
163 void JfrBuffer::move(JfrBuffer* const to, size_t size) {
164 assert(validate_to(to, size), "invariant");
165 assert(validate_this(this, size), "invariant");
166 const u1* current_top = top();
167 assert(current_top != NULL, "invariant");
168 memcpy(to->pos(), current_top, size);
169 to->set_pos(size);
170 to->release();
171 set_top(current_top + size);
172 }
173
174 void JfrBuffer::concurrent_move_and_reinitialize(JfrBuffer* const to, size_t size) {
175 assert(validate_to(to, size), "invariant");
176 const u1* current_top = concurrent_top();
177 assert(validate_concurrent_this(this, size), "invariant");
178 const size_t actual_size = MIN2(size, (size_t)(pos() - current_top));
179 assert(actual_size <= size, "invariant");
180 memcpy(to->pos(), current_top, actual_size);
181 to->set_pos(actual_size);
182 set_pos(start());
183 to->release();
184 set_concurrent_top(start());
185 }
186
187 // flags
188 enum FLAG {
189 RETIRED = 1,
190 TRANSIENT = 2,
191 LEASE = 4
192 };
193
194 bool JfrBuffer::transient() const {
195 return (u1)TRANSIENT == (_flags & (u1)TRANSIENT);
196 }
197
198 void JfrBuffer::set_transient() {
199 _flags |= (u1)TRANSIENT;
200 assert(transient(), "invariant");
201 }
202
203 void JfrBuffer::clear_transient() {
204 if (transient()) {
205 _flags ^= (u1)TRANSIENT;
206 }
207 assert(!transient(), "invariant");
208 }
209
210 bool JfrBuffer::lease() const {
211 return (u1)LEASE == (_flags & (u1)LEASE);
212 }
213
214 void JfrBuffer::set_lease() {
215 _flags |= (u1)LEASE;
216 assert(lease(), "invariant");
217 }
218
219 void JfrBuffer::clear_lease() {
220 if (lease()) {
221 _flags ^= (u1)LEASE;
222 }
223 assert(!lease(), "invariant");
224 }
225
226 static u2 load_acquire_flags(const u2* const flags) {
227 return OrderAccess::load_acquire((volatile jushort *)flags);
228 }
229
230 static void release_store_flags(u2* const flags, u2 new_flags) {
231 OrderAccess::release_store(flags, new_flags);
232 }
233
234 bool JfrBuffer::retired() const {
235 return (u1)RETIRED == (load_acquire_flags(&_flags) & (u1)RETIRED);
236 }
237
238 void JfrBuffer::set_retired() {
239 const u2 new_flags = load_acquire_flags(&_flags) | (u1)RETIRED;
240 release_store_flags(&_flags, new_flags);
241 }
242
243 void JfrBuffer::clear_retired() {
244 u2 new_flags = load_acquire_flags(&_flags);
245 if ((u1)RETIRED == (new_flags & (u1)RETIRED)) {
246 new_flags ^= (u1)RETIRED;
247 release_store_flags(&_flags, new_flags);
248 }
249 }