Andreas Gampe | 319dbe8 | 2017-01-09 16:42:21 -0800 | [diff] [blame^] | 1 | /* Copyright (C) 2017 The Android Open Source Project |
| 2 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 3 | * |
| 4 | * This file implements interfaces from the file jvmti.h. This implementation |
| 5 | * is licensed under the same terms as the file jvmti.h. The |
| 6 | * copyright and license information for the file jvmti.h follows. |
| 7 | * |
| 8 | * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved. |
| 9 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 10 | * |
| 11 | * This code is free software; you can redistribute it and/or modify it |
| 12 | * under the terms of the GNU General Public License version 2 only, as |
| 13 | * published by the Free Software Foundation. Oracle designates this |
| 14 | * particular file as subject to the "Classpath" exception as provided |
| 15 | * by Oracle in the LICENSE file that accompanied this code. |
| 16 | * |
| 17 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 20 | * version 2 for more details (a copy is included in the LICENSE file that |
| 21 | * accompanied this code). |
| 22 | * |
| 23 | * You should have received a copy of the GNU General Public License version |
| 24 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 25 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 26 | * |
| 27 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| 28 | * or visit www.oracle.com if you need additional information or have any |
| 29 | * questions. |
| 30 | */ |
| 31 | |
| 32 | #include "ti_monitor.h" |
| 33 | |
| 34 | #include <atomic> |
| 35 | #include <chrono> |
| 36 | #include <condition_variable> |
| 37 | #include <mutex> |
| 38 | |
| 39 | #include "art_jvmti.h" |
| 40 | #include "runtime.h" |
| 41 | #include "scoped_thread_state_change-inl.h" |
| 42 | #include "thread-inl.h" |
| 43 | |
| 44 | namespace openjdkjvmti { |
| 45 | |
| 46 | // We cannot use ART monitors, as they require the mutator lock for contention locking. We |
| 47 | // also cannot use pthread mutexes and condition variables (or C++11 abstractions) directly, |
| 48 | // as the do not have the right semantics for recursive mutexes and waiting (wait only unlocks |
| 49 | // the mutex once). |
| 50 | // So go ahead and use a wrapper that does the counting explicitly. |
| 51 | |
| 52 | class JvmtiMonitor { |
| 53 | public: |
| 54 | JvmtiMonitor() : owner_(nullptr), count_(0) { |
| 55 | } |
| 56 | |
| 57 | static bool Destroy(art::Thread* self, JvmtiMonitor* monitor) { |
| 58 | // Check whether this thread holds the monitor, or nobody does. |
| 59 | art::Thread* owner_thread = monitor->owner_.load(std::memory_order_relaxed); |
| 60 | if (owner_thread != nullptr && self != owner_thread) { |
| 61 | return false; |
| 62 | } |
| 63 | |
| 64 | if (monitor->count_ > 0) { |
| 65 | monitor->count_ = 0; |
| 66 | monitor->owner_.store(nullptr, std::memory_order_relaxed); |
| 67 | monitor->mutex_.unlock(); |
| 68 | } |
| 69 | |
| 70 | delete monitor; |
| 71 | return true; |
| 72 | } |
| 73 | |
| 74 | void MonitorEnter(art::Thread* self) { |
| 75 | // Check for recursive enter. |
| 76 | if (IsOwner(self)) { |
| 77 | count_++; |
| 78 | return; |
| 79 | } |
| 80 | |
| 81 | mutex_.lock(); |
| 82 | |
| 83 | DCHECK(owner_.load(std::memory_order_relaxed) == nullptr); |
| 84 | owner_.store(self, std::memory_order_relaxed); |
| 85 | DCHECK_EQ(0u, count_); |
| 86 | count_ = 1; |
| 87 | } |
| 88 | |
| 89 | bool MonitorExit(art::Thread* self) { |
| 90 | if (!IsOwner(self)) { |
| 91 | return false; |
| 92 | } |
| 93 | |
| 94 | --count_; |
| 95 | if (count_ == 0u) { |
| 96 | owner_.store(nullptr, std::memory_order_relaxed); |
| 97 | mutex_.unlock(); |
| 98 | } |
| 99 | |
| 100 | return true; |
| 101 | } |
| 102 | |
| 103 | bool Wait(art::Thread* self) { |
| 104 | auto wait_without_timeout = [&](std::unique_lock<std::mutex>& lk) { |
| 105 | cond_.wait(lk); |
| 106 | }; |
| 107 | return Wait(self, wait_without_timeout); |
| 108 | } |
| 109 | |
| 110 | bool Wait(art::Thread* self, uint64_t timeout_in_ms) { |
| 111 | auto wait_with_timeout = [&](std::unique_lock<std::mutex>& lk) { |
| 112 | cond_.wait_for(lk, std::chrono::milliseconds(timeout_in_ms)); |
| 113 | }; |
| 114 | return Wait(self, wait_with_timeout); |
| 115 | } |
| 116 | |
| 117 | bool Notify(art::Thread* self) { |
| 118 | return Notify(self, [&]() { cond_.notify_one(); }); |
| 119 | } |
| 120 | |
| 121 | bool NotifyAll(art::Thread* self) { |
| 122 | return Notify(self, [&]() { cond_.notify_all(); }); |
| 123 | } |
| 124 | |
| 125 | private: |
| 126 | bool IsOwner(art::Thread* self) { |
| 127 | // There's a subtle correctness argument here for a relaxed load outside the critical section. |
| 128 | // A thread is guaranteed to see either its own latest store or another thread's store. If a |
| 129 | // thread sees another thread's store than it cannot be holding the lock. |
| 130 | art::Thread* owner_thread = owner_.load(std::memory_order_relaxed); |
| 131 | return self == owner_thread; |
| 132 | } |
| 133 | |
| 134 | template <typename T> |
| 135 | bool Wait(art::Thread* self, T how_to_wait) { |
| 136 | if (!IsOwner(self)) { |
| 137 | return false; |
| 138 | } |
| 139 | |
| 140 | size_t old_count = count_; |
| 141 | |
| 142 | count_ = 0; |
| 143 | owner_.store(nullptr, std::memory_order_relaxed); |
| 144 | |
| 145 | { |
| 146 | std::unique_lock<std::mutex> lk(mutex_, std::adopt_lock); |
| 147 | how_to_wait(lk); |
| 148 | lk.release(); // Do not unlock the mutex. |
| 149 | } |
| 150 | |
| 151 | DCHECK(owner_.load(std::memory_order_relaxed) == nullptr); |
| 152 | owner_.store(self, std::memory_order_relaxed); |
| 153 | DCHECK_EQ(0u, count_); |
| 154 | count_ = old_count; |
| 155 | |
| 156 | return true; |
| 157 | } |
| 158 | |
| 159 | template <typename T> |
| 160 | bool Notify(art::Thread* self, T how_to_notify) { |
| 161 | if (!IsOwner(self)) { |
| 162 | return false; |
| 163 | } |
| 164 | |
| 165 | how_to_notify(); |
| 166 | |
| 167 | return true; |
| 168 | } |
| 169 | |
| 170 | std::mutex mutex_; |
| 171 | std::condition_variable cond_; |
| 172 | std::atomic<art::Thread*> owner_; |
| 173 | size_t count_; |
| 174 | }; |
| 175 | |
| 176 | static jrawMonitorID EncodeMonitor(JvmtiMonitor* monitor) { |
| 177 | return reinterpret_cast<jrawMonitorID>(monitor); |
| 178 | } |
| 179 | |
| 180 | static JvmtiMonitor* DecodeMonitor(jrawMonitorID id) { |
| 181 | return reinterpret_cast<JvmtiMonitor*>(id); |
| 182 | } |
| 183 | |
| 184 | jvmtiError MonitorUtil::CreateRawMonitor(jvmtiEnv* env ATTRIBUTE_UNUSED, |
| 185 | const char* name, |
| 186 | jrawMonitorID* monitor_ptr) { |
| 187 | if (name == nullptr || monitor_ptr == nullptr) { |
| 188 | return ERR(NULL_POINTER); |
| 189 | } |
| 190 | |
| 191 | JvmtiMonitor* monitor = new JvmtiMonitor(); |
| 192 | *monitor_ptr = EncodeMonitor(monitor); |
| 193 | |
| 194 | return ERR(NONE); |
| 195 | } |
| 196 | |
| 197 | jvmtiError MonitorUtil::DestroyRawMonitor(jvmtiEnv* env ATTRIBUTE_UNUSED, jrawMonitorID id) { |
| 198 | if (id == nullptr) { |
| 199 | return ERR(INVALID_MONITOR); |
| 200 | } |
| 201 | |
| 202 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 203 | art::Thread* self = art::Thread::Current(); |
| 204 | |
| 205 | if (!JvmtiMonitor::Destroy(self, monitor)) { |
| 206 | return ERR(NOT_MONITOR_OWNER); |
| 207 | } |
| 208 | |
| 209 | return ERR(NONE); |
| 210 | } |
| 211 | |
| 212 | jvmtiError MonitorUtil::RawMonitorEnter(jvmtiEnv* env ATTRIBUTE_UNUSED, jrawMonitorID id) { |
| 213 | if (id == nullptr) { |
| 214 | return ERR(INVALID_MONITOR); |
| 215 | } |
| 216 | |
| 217 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 218 | art::Thread* self = art::Thread::Current(); |
| 219 | |
| 220 | monitor->MonitorEnter(self); |
| 221 | |
| 222 | return ERR(NONE); |
| 223 | } |
| 224 | |
| 225 | jvmtiError MonitorUtil::RawMonitorExit(jvmtiEnv* env ATTRIBUTE_UNUSED, jrawMonitorID id) { |
| 226 | if (id == nullptr) { |
| 227 | return ERR(INVALID_MONITOR); |
| 228 | } |
| 229 | |
| 230 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 231 | art::Thread* self = art::Thread::Current(); |
| 232 | |
| 233 | if (!monitor->MonitorExit(self)) { |
| 234 | return ERR(NOT_MONITOR_OWNER); |
| 235 | } |
| 236 | |
| 237 | return ERR(NONE); |
| 238 | } |
| 239 | |
| 240 | jvmtiError MonitorUtil::RawMonitorWait(jvmtiEnv* env ATTRIBUTE_UNUSED, |
| 241 | jrawMonitorID id, |
| 242 | jlong millis) { |
| 243 | if (id == nullptr) { |
| 244 | return ERR(INVALID_MONITOR); |
| 245 | } |
| 246 | |
| 247 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 248 | art::Thread* self = art::Thread::Current(); |
| 249 | |
| 250 | // This is not in the spec, but it's the only thing that makes sense (and agrees with |
| 251 | // Object.wait). |
| 252 | if (millis < 0) { |
| 253 | return ERR(ILLEGAL_ARGUMENT); |
| 254 | } |
| 255 | |
| 256 | bool result = (millis > 0) |
| 257 | ? monitor->Wait(self, static_cast<uint64_t>(millis)) |
| 258 | : monitor->Wait(self); |
| 259 | |
| 260 | if (!result) { |
| 261 | return ERR(NOT_MONITOR_OWNER); |
| 262 | } |
| 263 | |
| 264 | // TODO: Make sure that is really what we should be checking here. |
| 265 | if (self->IsInterrupted()) { |
| 266 | return ERR(INTERRUPT); |
| 267 | } |
| 268 | |
| 269 | return ERR(NONE); |
| 270 | } |
| 271 | |
| 272 | jvmtiError MonitorUtil::RawMonitorNotify(jvmtiEnv* env ATTRIBUTE_UNUSED, jrawMonitorID id) { |
| 273 | if (id == nullptr) { |
| 274 | return ERR(INVALID_MONITOR); |
| 275 | } |
| 276 | |
| 277 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 278 | art::Thread* self = art::Thread::Current(); |
| 279 | |
| 280 | if (!monitor->Notify(self)) { |
| 281 | return ERR(NOT_MONITOR_OWNER); |
| 282 | } |
| 283 | |
| 284 | return ERR(NONE); |
| 285 | } |
| 286 | |
| 287 | jvmtiError MonitorUtil::RawMonitorNotifyAll(jvmtiEnv* env ATTRIBUTE_UNUSED, jrawMonitorID id) { |
| 288 | if (id == nullptr) { |
| 289 | return ERR(INVALID_MONITOR); |
| 290 | } |
| 291 | |
| 292 | JvmtiMonitor* monitor = DecodeMonitor(id); |
| 293 | art::Thread* self = art::Thread::Current(); |
| 294 | |
| 295 | if (!monitor->NotifyAll(self)) { |
| 296 | return ERR(NOT_MONITOR_OWNER); |
| 297 | } |
| 298 | |
| 299 | return ERR(NONE); |
| 300 | } |
| 301 | |
| 302 | } // namespace openjdkjvmti |