1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_THREAD_INL_H_ 18 #define ART_RUNTIME_THREAD_INL_H_ 19 20 #include "thread.h" 21 22 #ifdef ART_TARGET_ANDROID 23 #include <bionic_tls.h> // Access to our own TLS slot. 24 #endif 25 26 #include <pthread.h> 27 28 #include "base/casts.h" 29 #include "base/mutex-inl.h" 30 #include "gc/heap.h" 31 #include "jni_env_ext.h" 32 #include "obj_ptr.h" 33 #include "runtime.h" 34 #include "thread_pool.h" 35 36 namespace art { 37 38 // Quickly access the current thread from a JNIEnv. 39 static inline Thread* ThreadForEnv(JNIEnv* env) { 40 JNIEnvExt* full_env(down_cast<JNIEnvExt*>(env)); 41 return full_env->self; 42 } 43 44 inline Thread* Thread::Current() { 45 // We rely on Thread::Current returning null for a detached thread, so it's not obvious 46 // that we can replace this with a direct %fs access on x86. 47 if (!is_started_) { 48 return nullptr; 49 } else { 50 #ifdef ART_TARGET_ANDROID 51 void* thread = __get_tls()[TLS_SLOT_ART_THREAD_SELF]; 52 #else 53 void* thread = pthread_getspecific(Thread::pthread_key_self_); 54 #endif 55 return reinterpret_cast<Thread*>(thread); 56 } 57 } 58 59 inline void Thread::AllowThreadSuspension() { 60 DCHECK_EQ(Thread::Current(), this); 61 if (UNLIKELY(TestAllFlags())) { 62 CheckSuspend(); 63 } 64 // Invalidate the current thread's object pointers (ObjPtr) to catch possible moving GC bugs due 65 // to missing handles. 66 PoisonObjectPointers(); 67 } 68 69 inline void Thread::CheckSuspend() { 70 DCHECK_EQ(Thread::Current(), this); 71 for (;;) { 72 if (ReadFlag(kCheckpointRequest)) { 73 RunCheckpointFunction(); 74 } else if (ReadFlag(kSuspendRequest)) { 75 FullSuspendCheck(); 76 } else if (ReadFlag(kEmptyCheckpointRequest)) { 77 RunEmptyCheckpoint(); 78 } else { 79 break; 80 } 81 } 82 } 83 84 inline void Thread::CheckEmptyCheckpointFromWeakRefAccess(BaseMutex* cond_var_mutex) { 85 Thread* self = Thread::Current(); 86 DCHECK_EQ(self, this); 87 for (;;) { 88 if (ReadFlag(kEmptyCheckpointRequest)) { 89 RunEmptyCheckpoint(); 90 // Check we hold only an expected mutex when accessing weak ref. 91 if (kIsDebugBuild) { 92 for (int i = kLockLevelCount - 1; i >= 0; --i) { 93 BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i)); 94 if (held_mutex != nullptr && 95 held_mutex != Locks::mutator_lock_ && 96 held_mutex != cond_var_mutex) { 97 CHECK(Locks::IsExpectedOnWeakRefAccess(held_mutex)) 98 << "Holding unexpected mutex " << held_mutex->GetName() 99 << " when accessing weak ref"; 100 } 101 } 102 } 103 } else { 104 break; 105 } 106 } 107 } 108 109 inline void Thread::CheckEmptyCheckpointFromMutex() { 110 DCHECK_EQ(Thread::Current(), this); 111 for (;;) { 112 if (ReadFlag(kEmptyCheckpointRequest)) { 113 RunEmptyCheckpoint(); 114 } else { 115 break; 116 } 117 } 118 } 119 120 inline ThreadState Thread::SetState(ThreadState new_state) { 121 // Should only be used to change between suspended states. 122 // Cannot use this code to change into or from Runnable as changing to Runnable should 123 // fail if old_state_and_flags.suspend_request is true and changing from Runnable might 124 // miss passing an active suspend barrier. 125 DCHECK_NE(new_state, kRunnable); 126 if (kIsDebugBuild && this != Thread::Current()) { 127 std::string name; 128 GetThreadName(name); 129 LOG(FATAL) << "Thread \"" << name << "\"(" << this << " != Thread::Current()=" 130 << Thread::Current() << ") changing state to " << new_state; 131 } 132 union StateAndFlags old_state_and_flags; 133 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 134 CHECK_NE(old_state_and_flags.as_struct.state, kRunnable); 135 tls32_.state_and_flags.as_struct.state = new_state; 136 return static_cast<ThreadState>(old_state_and_flags.as_struct.state); 137 } 138 139 inline bool Thread::IsThreadSuspensionAllowable() const { 140 if (tls32_.no_thread_suspension != 0) { 141 return false; 142 } 143 for (int i = kLockLevelCount - 1; i >= 0; --i) { 144 if (i != kMutatorLock && GetHeldMutex(static_cast<LockLevel>(i)) != nullptr) { 145 return false; 146 } 147 } 148 return true; 149 } 150 151 inline void Thread::AssertThreadSuspensionIsAllowable(bool check_locks) const { 152 if (kIsDebugBuild) { 153 if (gAborting == 0) { 154 CHECK_EQ(0u, tls32_.no_thread_suspension) << tlsPtr_.last_no_thread_suspension_cause; 155 } 156 if (check_locks) { 157 bool bad_mutexes_held = false; 158 for (int i = kLockLevelCount - 1; i >= 0; --i) { 159 // We expect no locks except the mutator_lock_ or thread list suspend thread lock. 160 if (i != kMutatorLock) { 161 BaseMutex* held_mutex = GetHeldMutex(static_cast<LockLevel>(i)); 162 if (held_mutex != nullptr) { 163 LOG(ERROR) << "holding \"" << held_mutex->GetName() 164 << "\" at point where thread suspension is expected"; 165 bad_mutexes_held = true; 166 } 167 } 168 } 169 if (gAborting == 0) { 170 CHECK(!bad_mutexes_held); 171 } 172 } 173 } 174 } 175 176 inline void Thread::TransitionToSuspendedAndRunCheckpoints(ThreadState new_state) { 177 DCHECK_NE(new_state, kRunnable); 178 DCHECK_EQ(GetState(), kRunnable); 179 union StateAndFlags old_state_and_flags; 180 union StateAndFlags new_state_and_flags; 181 while (true) { 182 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 183 if (UNLIKELY((old_state_and_flags.as_struct.flags & kCheckpointRequest) != 0)) { 184 RunCheckpointFunction(); 185 continue; 186 } 187 if (UNLIKELY((old_state_and_flags.as_struct.flags & kEmptyCheckpointRequest) != 0)) { 188 RunEmptyCheckpoint(); 189 continue; 190 } 191 // Change the state but keep the current flags (kCheckpointRequest is clear). 192 DCHECK_EQ((old_state_and_flags.as_struct.flags & kCheckpointRequest), 0); 193 DCHECK_EQ((old_state_and_flags.as_struct.flags & kEmptyCheckpointRequest), 0); 194 new_state_and_flags.as_struct.flags = old_state_and_flags.as_struct.flags; 195 new_state_and_flags.as_struct.state = new_state; 196 197 // CAS the value with a memory ordering. 198 bool done = 199 tls32_.state_and_flags.as_atomic_int.CompareExchangeWeakRelease(old_state_and_flags.as_int, 200 new_state_and_flags.as_int); 201 if (LIKELY(done)) { 202 break; 203 } 204 } 205 } 206 207 inline void Thread::PassActiveSuspendBarriers() { 208 while (true) { 209 uint16_t current_flags = tls32_.state_and_flags.as_struct.flags; 210 if (LIKELY((current_flags & 211 (kCheckpointRequest | kEmptyCheckpointRequest | kActiveSuspendBarrier)) == 0)) { 212 break; 213 } else if ((current_flags & kActiveSuspendBarrier) != 0) { 214 PassActiveSuspendBarriers(this); 215 } else { 216 // Impossible 217 LOG(FATAL) << "Fatal, thread transitioned into suspended without running the checkpoint"; 218 } 219 } 220 } 221 222 inline void Thread::TransitionFromRunnableToSuspended(ThreadState new_state) { 223 AssertThreadSuspensionIsAllowable(); 224 PoisonObjectPointersIfDebug(); 225 DCHECK_EQ(this, Thread::Current()); 226 // Change to non-runnable state, thereby appearing suspended to the system. 227 TransitionToSuspendedAndRunCheckpoints(new_state); 228 // Mark the release of the share of the mutator_lock_. 229 Locks::mutator_lock_->TransitionFromRunnableToSuspended(this); 230 // Once suspended - check the active suspend barrier flag 231 PassActiveSuspendBarriers(); 232 } 233 234 inline ThreadState Thread::TransitionFromSuspendedToRunnable() { 235 union StateAndFlags old_state_and_flags; 236 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 237 int16_t old_state = old_state_and_flags.as_struct.state; 238 DCHECK_NE(static_cast<ThreadState>(old_state), kRunnable); 239 do { 240 Locks::mutator_lock_->AssertNotHeld(this); // Otherwise we starve GC.. 241 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 242 DCHECK_EQ(old_state_and_flags.as_struct.state, old_state); 243 if (LIKELY(old_state_and_flags.as_struct.flags == 0)) { 244 // Optimize for the return from native code case - this is the fast path. 245 // Atomically change from suspended to runnable if no suspend request pending. 246 union StateAndFlags new_state_and_flags; 247 new_state_and_flags.as_int = old_state_and_flags.as_int; 248 new_state_and_flags.as_struct.state = kRunnable; 249 // CAS the value with a memory barrier. 250 if (LIKELY(tls32_.state_and_flags.as_atomic_int.CompareExchangeWeakAcquire( 251 old_state_and_flags.as_int, 252 new_state_and_flags.as_int))) { 253 // Mark the acquisition of a share of the mutator_lock_. 254 Locks::mutator_lock_->TransitionFromSuspendedToRunnable(this); 255 break; 256 } 257 } else if ((old_state_and_flags.as_struct.flags & kActiveSuspendBarrier) != 0) { 258 PassActiveSuspendBarriers(this); 259 } else if ((old_state_and_flags.as_struct.flags & 260 (kCheckpointRequest | kEmptyCheckpointRequest)) != 0) { 261 // Impossible 262 LOG(FATAL) << "Transitioning to runnable with checkpoint flag, " 263 << " flags=" << old_state_and_flags.as_struct.flags 264 << " state=" << old_state_and_flags.as_struct.state; 265 } else if ((old_state_and_flags.as_struct.flags & kSuspendRequest) != 0) { 266 // Wait while our suspend count is non-zero. 267 268 // We pass null to the MutexLock as we may be in a situation where the 269 // runtime is shutting down. Guarding ourselves from that situation 270 // requires to take the shutdown lock, which is undesirable here. 271 Thread* thread_to_pass = nullptr; 272 if (kIsDebugBuild && !IsDaemon()) { 273 // We know we can make our debug locking checks on non-daemon threads, 274 // so re-enable them on debug builds. 275 thread_to_pass = this; 276 } 277 MutexLock mu(thread_to_pass, *Locks::thread_suspend_count_lock_); 278 ScopedTransitioningToRunnable scoped_transitioning_to_runnable(this); 279 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 280 DCHECK_EQ(old_state_and_flags.as_struct.state, old_state); 281 while ((old_state_and_flags.as_struct.flags & kSuspendRequest) != 0) { 282 // Re-check when Thread::resume_cond_ is notified. 283 Thread::resume_cond_->Wait(thread_to_pass); 284 old_state_and_flags.as_int = tls32_.state_and_flags.as_int; 285 DCHECK_EQ(old_state_and_flags.as_struct.state, old_state); 286 } 287 DCHECK_EQ(GetSuspendCount(), 0); 288 } 289 } while (true); 290 // Run the flip function, if set. 291 Closure* flip_func = GetFlipFunction(); 292 if (flip_func != nullptr) { 293 flip_func->Run(this); 294 } 295 return static_cast<ThreadState>(old_state); 296 } 297 298 inline void Thread::VerifyStack() { 299 if (kVerifyStack) { 300 if (Runtime::Current()->GetHeap()->IsObjectValidationEnabled()) { 301 VerifyStackImpl(); 302 } 303 } 304 } 305 306 inline mirror::Object* Thread::AllocTlab(size_t bytes) { 307 DCHECK_GE(TlabSize(), bytes); 308 ++tlsPtr_.thread_local_objects; 309 mirror::Object* ret = reinterpret_cast<mirror::Object*>(tlsPtr_.thread_local_pos); 310 tlsPtr_.thread_local_pos += bytes; 311 return ret; 312 } 313 314 inline bool Thread::PushOnThreadLocalAllocationStack(mirror::Object* obj) { 315 DCHECK_LE(tlsPtr_.thread_local_alloc_stack_top, tlsPtr_.thread_local_alloc_stack_end); 316 if (tlsPtr_.thread_local_alloc_stack_top < tlsPtr_.thread_local_alloc_stack_end) { 317 // There's room. 318 DCHECK_LE(reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_top) + 319 sizeof(StackReference<mirror::Object>), 320 reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_end)); 321 DCHECK(tlsPtr_.thread_local_alloc_stack_top->AsMirrorPtr() == nullptr); 322 tlsPtr_.thread_local_alloc_stack_top->Assign(obj); 323 ++tlsPtr_.thread_local_alloc_stack_top; 324 return true; 325 } 326 return false; 327 } 328 329 inline void Thread::SetThreadLocalAllocationStack(StackReference<mirror::Object>* start, 330 StackReference<mirror::Object>* end) { 331 DCHECK(Thread::Current() == this) << "Should be called by self"; 332 DCHECK(start != nullptr); 333 DCHECK(end != nullptr); 334 DCHECK_ALIGNED(start, sizeof(StackReference<mirror::Object>)); 335 DCHECK_ALIGNED(end, sizeof(StackReference<mirror::Object>)); 336 DCHECK_LT(start, end); 337 tlsPtr_.thread_local_alloc_stack_end = end; 338 tlsPtr_.thread_local_alloc_stack_top = start; 339 } 340 341 inline void Thread::RevokeThreadLocalAllocationStack() { 342 if (kIsDebugBuild) { 343 // Note: self is not necessarily equal to this thread since thread may be suspended. 344 Thread* self = Thread::Current(); 345 DCHECK(this == self || IsSuspended() || GetState() == kWaitingPerformingGc) 346 << GetState() << " thread " << this << " self " << self; 347 } 348 tlsPtr_.thread_local_alloc_stack_end = nullptr; 349 tlsPtr_.thread_local_alloc_stack_top = nullptr; 350 } 351 352 inline void Thread::PoisonObjectPointersIfDebug() { 353 if (kObjPtrPoisoning) { 354 Thread::Current()->PoisonObjectPointers(); 355 } 356 } 357 358 inline bool Thread::ModifySuspendCount(Thread* self, 359 int delta, 360 AtomicInteger* suspend_barrier, 361 bool for_debugger) { 362 if (delta > 0 && ((kUseReadBarrier && this != self) || suspend_barrier != nullptr)) { 363 // When delta > 0 (requesting a suspend), ModifySuspendCountInternal() may fail either if 364 // active_suspend_barriers is full or we are in the middle of a thread flip. Retry in a loop. 365 while (true) { 366 if (LIKELY(ModifySuspendCountInternal(self, delta, suspend_barrier, for_debugger))) { 367 return true; 368 } else { 369 // Failure means the list of active_suspend_barriers is full or we are in the middle of a 370 // thread flip, we should release the thread_suspend_count_lock_ (to avoid deadlock) and 371 // wait till the target thread has executed or Thread::PassActiveSuspendBarriers() or the 372 // flip function. Note that we could not simply wait for the thread to change to a suspended 373 // state, because it might need to run checkpoint function before the state change or 374 // resumes from the resume_cond_, which also needs thread_suspend_count_lock_. 375 // 376 // The list of active_suspend_barriers is very unlikely to be full since more than 377 // kMaxSuspendBarriers threads need to execute SuspendAllInternal() simultaneously, and 378 // target thread stays in kRunnable in the mean time. 379 Locks::thread_suspend_count_lock_->ExclusiveUnlock(self); 380 NanoSleep(100000); 381 Locks::thread_suspend_count_lock_->ExclusiveLock(self); 382 } 383 } 384 } else { 385 return ModifySuspendCountInternal(self, delta, suspend_barrier, for_debugger); 386 } 387 } 388 389 } // namespace art 390 391 #endif // ART_RUNTIME_THREAD_INL_H_ 392
