| File: | out/../deps/v8/src/execution/v8threads.cc |
| Warning: | line 279, column 3 Value stored to 'to' is never read |
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| 1 | // Copyright 2012 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/execution/v8threads.h" |
| 6 | |
| 7 | #include "include/v8-locker.h" |
| 8 | #include "src/api/api.h" |
| 9 | #include "src/debug/debug.h" |
| 10 | #include "src/execution/execution.h" |
| 11 | #include "src/execution/isolate-inl.h" |
| 12 | #include "src/execution/stack-guard.h" |
| 13 | #include "src/init/bootstrapper.h" |
| 14 | #include "src/objects/visitors.h" |
| 15 | #include "src/regexp/regexp-stack.h" |
| 16 | |
| 17 | namespace v8 { |
| 18 | |
| 19 | namespace { |
| 20 | |
| 21 | // Track whether this V8 instance has ever called v8::Locker. This allows the |
| 22 | // API code to verify that the lock is always held when V8 is being entered. |
| 23 | base::AtomicWord g_locker_was_ever_used_ = 0; |
| 24 | |
| 25 | } // namespace |
| 26 | |
| 27 | // Once the Locker is initialized, the current thread will be guaranteed to have |
| 28 | // the lock for a given isolate. |
| 29 | void Locker::Initialize(v8::Isolate* isolate) { |
| 30 | DCHECK_NOT_NULL(isolate)((void) 0); |
| 31 | has_lock_ = false; |
| 32 | top_level_ = true; |
| 33 | isolate_ = reinterpret_cast<i::Isolate*>(isolate); |
| 34 | |
| 35 | // Record that the Locker has been used at least once. |
| 36 | base::Relaxed_Store(&g_locker_was_ever_used_, 1); |
| 37 | isolate_->set_was_locker_ever_used(); |
| 38 | |
| 39 | // Get the big lock if necessary. |
| 40 | if (!isolate_->thread_manager()->IsLockedByCurrentThread()) { |
| 41 | isolate_->thread_manager()->Lock(); |
| 42 | has_lock_ = true; |
| 43 | |
| 44 | // This may be a locker within an unlocker in which case we have to |
| 45 | // get the saved state for this thread and restore it. |
| 46 | if (isolate_->thread_manager()->RestoreThread()) { |
| 47 | top_level_ = false; |
| 48 | } |
| 49 | } |
| 50 | DCHECK(isolate_->thread_manager()->IsLockedByCurrentThread())((void) 0); |
| 51 | } |
| 52 | |
| 53 | bool Locker::IsLocked(v8::Isolate* isolate) { |
| 54 | DCHECK_NOT_NULL(isolate)((void) 0); |
| 55 | i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate); |
| 56 | return internal_isolate->thread_manager()->IsLockedByCurrentThread(); |
| 57 | } |
| 58 | |
| 59 | // static |
| 60 | bool Locker::IsActive() { return WasEverUsed(); } |
| 61 | |
| 62 | // static |
| 63 | bool Locker::WasEverUsed() { |
| 64 | return base::Relaxed_Load(&g_locker_was_ever_used_) != 0; |
| 65 | } |
| 66 | |
| 67 | Locker::~Locker() { |
| 68 | DCHECK(isolate_->thread_manager()->IsLockedByCurrentThread())((void) 0); |
| 69 | if (has_lock_) { |
| 70 | if (top_level_) { |
| 71 | isolate_->thread_manager()->FreeThreadResources(); |
| 72 | } else { |
| 73 | isolate_->thread_manager()->ArchiveThread(); |
| 74 | } |
| 75 | isolate_->thread_manager()->Unlock(); |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | void Unlocker::Initialize(v8::Isolate* isolate) { |
| 80 | DCHECK_NOT_NULL(isolate)((void) 0); |
| 81 | isolate_ = reinterpret_cast<i::Isolate*>(isolate); |
| 82 | DCHECK(isolate_->thread_manager()->IsLockedByCurrentThread())((void) 0); |
| 83 | isolate_->thread_manager()->ArchiveThread(); |
| 84 | isolate_->thread_manager()->Unlock(); |
| 85 | } |
| 86 | |
| 87 | Unlocker::~Unlocker() { |
| 88 | DCHECK(!isolate_->thread_manager()->IsLockedByCurrentThread())((void) 0); |
| 89 | isolate_->thread_manager()->Lock(); |
| 90 | isolate_->thread_manager()->RestoreThread(); |
| 91 | } |
| 92 | |
| 93 | namespace internal { |
| 94 | |
| 95 | void ThreadManager::InitThread(const ExecutionAccess& lock) { |
| 96 | isolate_->InitializeThreadLocal(); |
| 97 | isolate_->stack_guard()->InitThread(lock); |
| 98 | isolate_->debug()->InitThread(lock); |
| 99 | } |
| 100 | |
| 101 | bool ThreadManager::RestoreThread() { |
| 102 | DCHECK(IsLockedByCurrentThread())((void) 0); |
| 103 | // First check whether the current thread has been 'lazily archived', i.e. |
| 104 | // not archived at all. If that is the case we put the state storage we |
| 105 | // had prepared back in the free list, since we didn't need it after all. |
| 106 | if (lazily_archived_thread_ == ThreadId::Current()) { |
| 107 | lazily_archived_thread_ = ThreadId::Invalid(); |
| 108 | Isolate::PerIsolateThreadData* per_thread = |
| 109 | isolate_->FindPerThreadDataForThisThread(); |
| 110 | DCHECK_NOT_NULL(per_thread)((void) 0); |
| 111 | DCHECK(per_thread->thread_state() == lazily_archived_thread_state_)((void) 0); |
| 112 | lazily_archived_thread_state_->set_id(ThreadId::Invalid()); |
| 113 | lazily_archived_thread_state_->LinkInto(ThreadState::FREE_LIST); |
| 114 | lazily_archived_thread_state_ = nullptr; |
| 115 | per_thread->set_thread_state(nullptr); |
| 116 | return true; |
| 117 | } |
| 118 | |
| 119 | // Make sure that the preemption thread cannot modify the thread state while |
| 120 | // it is being archived or restored. |
| 121 | ExecutionAccess access(isolate_); |
| 122 | |
| 123 | // If there is another thread that was lazily archived then we have to really |
| 124 | // archive it now. |
| 125 | if (lazily_archived_thread_.IsValid()) { |
| 126 | EagerlyArchiveThread(); |
| 127 | } |
| 128 | Isolate::PerIsolateThreadData* per_thread = |
| 129 | isolate_->FindPerThreadDataForThisThread(); |
| 130 | if (per_thread == nullptr || per_thread->thread_state() == nullptr) { |
| 131 | // This is a new thread. |
| 132 | InitThread(access); |
| 133 | return false; |
| 134 | } |
| 135 | ThreadState* state = per_thread->thread_state(); |
| 136 | char* from = state->data(); |
| 137 | from = isolate_->handle_scope_implementer()->RestoreThread(from); |
| 138 | from = isolate_->RestoreThread(from); |
| 139 | from = Relocatable::RestoreState(isolate_, from); |
| 140 | // Stack guard should be restored before Debug, etc. since Debug etc. might |
| 141 | // depend on a correct stack guard. |
| 142 | from = isolate_->stack_guard()->RestoreStackGuard(from); |
| 143 | from = isolate_->debug()->RestoreDebug(from); |
| 144 | from = isolate_->regexp_stack()->RestoreStack(from); |
| 145 | from = isolate_->bootstrapper()->RestoreState(from); |
| 146 | per_thread->set_thread_state(nullptr); |
| 147 | state->set_id(ThreadId::Invalid()); |
| 148 | state->Unlink(); |
| 149 | state->LinkInto(ThreadState::FREE_LIST); |
| 150 | return true; |
| 151 | } |
| 152 | |
| 153 | void ThreadManager::Lock() { |
| 154 | mutex_.Lock(); |
| 155 | mutex_owner_.store(ThreadId::Current(), std::memory_order_relaxed); |
| 156 | DCHECK(IsLockedByCurrentThread())((void) 0); |
| 157 | } |
| 158 | |
| 159 | void ThreadManager::Unlock() { |
| 160 | mutex_owner_.store(ThreadId::Invalid(), std::memory_order_relaxed); |
| 161 | mutex_.Unlock(); |
| 162 | } |
| 163 | |
| 164 | static int ArchiveSpacePerThread() { |
| 165 | return HandleScopeImplementer::ArchiveSpacePerThread() + |
| 166 | Isolate::ArchiveSpacePerThread() + Debug::ArchiveSpacePerThread() + |
| 167 | StackGuard::ArchiveSpacePerThread() + |
| 168 | RegExpStack::ArchiveSpacePerThread() + |
| 169 | Bootstrapper::ArchiveSpacePerThread() + |
| 170 | Relocatable::ArchiveSpacePerThread(); |
| 171 | } |
| 172 | |
| 173 | ThreadState::ThreadState(ThreadManager* thread_manager) |
| 174 | : id_(ThreadId::Invalid()), |
| 175 | data_(nullptr), |
| 176 | next_(this), |
| 177 | previous_(this), |
| 178 | thread_manager_(thread_manager) {} |
| 179 | |
| 180 | ThreadState::~ThreadState() { DeleteArray<char>(data_); } |
| 181 | |
| 182 | void ThreadState::AllocateSpace() { |
| 183 | data_ = NewArray<char>(ArchiveSpacePerThread()); |
| 184 | } |
| 185 | |
| 186 | void ThreadState::Unlink() { |
| 187 | next_->previous_ = previous_; |
| 188 | previous_->next_ = next_; |
| 189 | } |
| 190 | |
| 191 | void ThreadState::LinkInto(List list) { |
| 192 | ThreadState* flying_anchor = list == FREE_LIST |
| 193 | ? thread_manager_->free_anchor_ |
| 194 | : thread_manager_->in_use_anchor_; |
| 195 | next_ = flying_anchor->next_; |
| 196 | previous_ = flying_anchor; |
| 197 | flying_anchor->next_ = this; |
| 198 | next_->previous_ = this; |
| 199 | } |
| 200 | |
| 201 | ThreadState* ThreadManager::GetFreeThreadState() { |
| 202 | ThreadState* gotten = free_anchor_->next_; |
| 203 | if (gotten == free_anchor_) { |
| 204 | ThreadState* new_thread_state = new ThreadState(this); |
| 205 | new_thread_state->AllocateSpace(); |
| 206 | return new_thread_state; |
| 207 | } |
| 208 | return gotten; |
| 209 | } |
| 210 | |
| 211 | // Gets the first in the list of archived threads. |
| 212 | ThreadState* ThreadManager::FirstThreadStateInUse() { |
| 213 | return in_use_anchor_->Next(); |
| 214 | } |
| 215 | |
| 216 | ThreadState* ThreadState::Next() { |
| 217 | if (next_ == thread_manager_->in_use_anchor_) return nullptr; |
| 218 | return next_; |
| 219 | } |
| 220 | |
| 221 | // Thread ids must start with 1, because in TLS having thread id 0 can't |
| 222 | // be distinguished from not having a thread id at all (since NULL is |
| 223 | // defined as 0.) |
| 224 | ThreadManager::ThreadManager(Isolate* isolate) |
| 225 | : mutex_owner_(ThreadId::Invalid()), |
| 226 | lazily_archived_thread_(ThreadId::Invalid()), |
| 227 | lazily_archived_thread_state_(nullptr), |
| 228 | free_anchor_(nullptr), |
| 229 | in_use_anchor_(nullptr), |
| 230 | isolate_(isolate) { |
| 231 | free_anchor_ = new ThreadState(this); |
| 232 | in_use_anchor_ = new ThreadState(this); |
| 233 | } |
| 234 | |
| 235 | ThreadManager::~ThreadManager() { |
| 236 | DeleteThreadStateList(free_anchor_); |
| 237 | DeleteThreadStateList(in_use_anchor_); |
| 238 | } |
| 239 | |
| 240 | void ThreadManager::DeleteThreadStateList(ThreadState* anchor) { |
| 241 | // The list starts and ends with the anchor. |
| 242 | for (ThreadState* current = anchor->next_; current != anchor;) { |
| 243 | ThreadState* next = current->next_; |
| 244 | delete current; |
| 245 | current = next; |
| 246 | } |
| 247 | delete anchor; |
| 248 | } |
| 249 | |
| 250 | void ThreadManager::ArchiveThread() { |
| 251 | DCHECK_EQ(lazily_archived_thread_, ThreadId::Invalid())((void) 0); |
| 252 | DCHECK(!IsArchived())((void) 0); |
| 253 | DCHECK(IsLockedByCurrentThread())((void) 0); |
| 254 | ThreadState* state = GetFreeThreadState(); |
| 255 | state->Unlink(); |
| 256 | Isolate::PerIsolateThreadData* per_thread = |
| 257 | isolate_->FindOrAllocatePerThreadDataForThisThread(); |
| 258 | per_thread->set_thread_state(state); |
| 259 | lazily_archived_thread_ = ThreadId::Current(); |
| 260 | lazily_archived_thread_state_ = state; |
| 261 | DCHECK_EQ(state->id(), ThreadId::Invalid())((void) 0); |
| 262 | state->set_id(CurrentId()); |
| 263 | DCHECK_NE(state->id(), ThreadId::Invalid())((void) 0); |
| 264 | } |
| 265 | |
| 266 | void ThreadManager::EagerlyArchiveThread() { |
| 267 | DCHECK(IsLockedByCurrentThread())((void) 0); |
| 268 | ThreadState* state = lazily_archived_thread_state_; |
| 269 | state->LinkInto(ThreadState::IN_USE_LIST); |
| 270 | char* to = state->data(); |
| 271 | // Ensure that data containing GC roots are archived first, and handle them |
| 272 | // in ThreadManager::Iterate(RootVisitor*). |
| 273 | to = isolate_->handle_scope_implementer()->ArchiveThread(to); |
| 274 | to = isolate_->ArchiveThread(to); |
| 275 | to = Relocatable::ArchiveState(isolate_, to); |
| 276 | to = isolate_->stack_guard()->ArchiveStackGuard(to); |
| 277 | to = isolate_->debug()->ArchiveDebug(to); |
| 278 | to = isolate_->regexp_stack()->ArchiveStack(to); |
| 279 | to = isolate_->bootstrapper()->ArchiveState(to); |
Value stored to 'to' is never read | |
| 280 | lazily_archived_thread_ = ThreadId::Invalid(); |
| 281 | lazily_archived_thread_state_ = nullptr; |
| 282 | } |
| 283 | |
| 284 | void ThreadManager::FreeThreadResources() { |
| 285 | DCHECK(!isolate_->has_pending_exception())((void) 0); |
| 286 | DCHECK(!isolate_->external_caught_exception())((void) 0); |
| 287 | DCHECK_NULL(isolate_->try_catch_handler())((void) 0); |
| 288 | isolate_->handle_scope_implementer()->FreeThreadResources(); |
| 289 | isolate_->FreeThreadResources(); |
| 290 | isolate_->debug()->FreeThreadResources(); |
| 291 | isolate_->stack_guard()->FreeThreadResources(); |
| 292 | isolate_->regexp_stack()->FreeThreadResources(); |
| 293 | isolate_->bootstrapper()->FreeThreadResources(); |
| 294 | } |
| 295 | |
| 296 | bool ThreadManager::IsArchived() { |
| 297 | Isolate::PerIsolateThreadData* data = |
| 298 | isolate_->FindPerThreadDataForThisThread(); |
| 299 | return data != nullptr && data->thread_state() != nullptr; |
| 300 | } |
| 301 | |
| 302 | void ThreadManager::Iterate(RootVisitor* v) { |
| 303 | // Expecting no threads during serialization/deserialization |
| 304 | for (ThreadState* state = FirstThreadStateInUse(); state != nullptr; |
| 305 | state = state->Next()) { |
| 306 | char* data = state->data(); |
| 307 | data = HandleScopeImplementer::Iterate(v, data); |
| 308 | data = isolate_->Iterate(v, data); |
| 309 | data = Relocatable::Iterate(v, data); |
| 310 | data = StackGuard::Iterate(v, data); |
| 311 | data = Debug::Iterate(v, data); |
| 312 | } |
| 313 | } |
| 314 | |
| 315 | void ThreadManager::IterateArchivedThreads(ThreadVisitor* v) { |
| 316 | for (ThreadState* state = FirstThreadStateInUse(); state != nullptr; |
| 317 | state = state->Next()) { |
| 318 | char* data = state->data(); |
| 319 | data += HandleScopeImplementer::ArchiveSpacePerThread(); |
| 320 | isolate_->IterateThread(v, data); |
| 321 | } |
| 322 | } |
| 323 | |
| 324 | ThreadId ThreadManager::CurrentId() { return ThreadId::Current(); } |
| 325 | |
| 326 | } // namespace internal |
| 327 | } // namespace v8 |