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// Copyright 2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "v8.h"
#include "api.h"
#include "bootstrapper.h"
#include "debug.h"
#include "execution.h"
#include "v8threads.h"
#include "regexp-stack.h"
namespace v8 {
static internal::Thread::LocalStorageKey thread_state_key =
internal::Thread::CreateThreadLocalKey();
static internal::Thread::LocalStorageKey thread_id_key =
internal::Thread::CreateThreadLocalKey();
// Track whether this V8 instance has ever called v8::Locker. This allows the
// API code to verify that the lock is always held when V8 is being entered.
bool Locker::active_ = false;
// Constructor for the Locker object. Once the Locker is constructed the
// current thread will be guaranteed to have the big V8 lock.
Locker::Locker() : has_lock_(false), top_level_(true) {
// Record that the Locker has been used at least once.
active_ = true;
// Get the big lock if necessary.
if (!internal::ThreadManager::IsLockedByCurrentThread()) {
internal::ThreadManager::Lock();
has_lock_ = true;
// Make sure that V8 is initialized. Archiving of threads interferes
// with deserialization by adding additional root pointers, so we must
// initialize here, before anyone can call ~Locker() or Unlocker().
if (!internal::V8::IsRunning()) {
V8::Initialize();
}
// This may be a locker within an unlocker in which case we have to
// get the saved state for this thread and restore it.
if (internal::ThreadManager::RestoreThread()) {
top_level_ = false;
} else {
internal::ExecutionAccess access;
internal::StackGuard::ClearThread(access);
internal::StackGuard::InitThread(access);
}
}
ASSERT(internal::ThreadManager::IsLockedByCurrentThread());
// Make sure this thread is assigned a thread id.
internal::ThreadManager::AssignId();
}
bool Locker::IsLocked() {
return internal::ThreadManager::IsLockedByCurrentThread();
}
Locker::~Locker() {
ASSERT(internal::ThreadManager::IsLockedByCurrentThread());
if (has_lock_) {
if (top_level_) {
internal::ThreadManager::FreeThreadResources();
} else {
internal::ThreadManager::ArchiveThread();
}
internal::ThreadManager::Unlock();
}
}
Unlocker::Unlocker() {
ASSERT(internal::ThreadManager::IsLockedByCurrentThread());
internal::ThreadManager::ArchiveThread();
internal::ThreadManager::Unlock();
}
Unlocker::~Unlocker() {
ASSERT(!internal::ThreadManager::IsLockedByCurrentThread());
internal::ThreadManager::Lock();
internal::ThreadManager::RestoreThread();
}
void Locker::StartPreemption(int every_n_ms) {
v8::internal::ContextSwitcher::StartPreemption(every_n_ms);
}
void Locker::StopPreemption() {
v8::internal::ContextSwitcher::StopPreemption();
}
namespace internal {
bool ThreadManager::RestoreThread() {
// First check whether the current thread has been 'lazily archived', ie
// not archived at all. If that is the case we put the state storage we
// had prepared back in the free list, since we didn't need it after all.
if (lazily_archived_thread_.IsSelf()) {
lazily_archived_thread_.Initialize(ThreadHandle::INVALID);
ASSERT(Thread::GetThreadLocal(thread_state_key) ==
lazily_archived_thread_state_);
lazily_archived_thread_state_->set_id(kInvalidId);
lazily_archived_thread_state_->LinkInto(ThreadState::FREE_LIST);
lazily_archived_thread_state_ = NULL;
Thread::SetThreadLocal(thread_state_key, NULL);
return true;
}
// Make sure that the preemption thread cannot modify the thread state while
// it is being archived or restored.
ExecutionAccess access;
// If there is another thread that was lazily archived then we have to really
// archive it now.
if (lazily_archived_thread_.IsValid()) {
EagerlyArchiveThread();
}
ThreadState* state =
reinterpret_cast<ThreadState*>(Thread::GetThreadLocal(thread_state_key));
if (state == NULL) {
// This is a new thread.
StackGuard::InitThread(access);
return false;
}
char* from = state->data();
from = HandleScopeImplementer::RestoreThread(from);
from = Top::RestoreThread(from);
from = Relocatable::RestoreState(from);
#ifdef ENABLE_DEBUGGER_SUPPORT
from = Debug::RestoreDebug(from);
#endif
from = StackGuard::RestoreStackGuard(from);
from = RegExpStack::RestoreStack(from);
from = Bootstrapper::RestoreState(from);
Thread::SetThreadLocal(thread_state_key, NULL);
if (state->terminate_on_restore()) {
StackGuard::TerminateExecution();
state->set_terminate_on_restore(false);
}
state->set_id(kInvalidId);
state->Unlink();
state->LinkInto(ThreadState::FREE_LIST);
return true;
}
void ThreadManager::Lock() {
mutex_->Lock();
mutex_owner_.Initialize(ThreadHandle::SELF);
ASSERT(IsLockedByCurrentThread());
}
void ThreadManager::Unlock() {
mutex_owner_.Initialize(ThreadHandle::INVALID);
mutex_->Unlock();
}
static int ArchiveSpacePerThread() {
return HandleScopeImplementer::ArchiveSpacePerThread() +
Top::ArchiveSpacePerThread() +
#ifdef ENABLE_DEBUGGER_SUPPORT
Debug::ArchiveSpacePerThread() +
#endif
StackGuard::ArchiveSpacePerThread() +
RegExpStack::ArchiveSpacePerThread() +
Bootstrapper::ArchiveSpacePerThread() +
Relocatable::ArchiveSpacePerThread();
}
ThreadState* ThreadState::free_anchor_ = new ThreadState();
ThreadState* ThreadState::in_use_anchor_ = new ThreadState();
ThreadState::ThreadState() : id_(ThreadManager::kInvalidId),
terminate_on_restore_(false),
next_(this), previous_(this) {
}
void ThreadState::AllocateSpace() {
data_ = NewArray<char>(ArchiveSpacePerThread());
}
void ThreadState::Unlink() {
next_->previous_ = previous_;
previous_->next_ = next_;
}
void ThreadState::LinkInto(List list) {
ThreadState* flying_anchor =
list == FREE_LIST ? free_anchor_ : in_use_anchor_;
next_ = flying_anchor->next_;
previous_ = flying_anchor;
flying_anchor->next_ = this;
next_->previous_ = this;
}
ThreadState* ThreadState::GetFree() {
ThreadState* gotten = free_anchor_->next_;
if (gotten == free_anchor_) {
ThreadState* new_thread_state = new ThreadState();
new_thread_state->AllocateSpace();
return new_thread_state;
}
return gotten;
}
// Gets the first in the list of archived threads.
ThreadState* ThreadState::FirstInUse() {
return in_use_anchor_->Next();
}
ThreadState* ThreadState::Next() {
if (next_ == in_use_anchor_) return NULL;
return next_;
}
// Thread ids must start with 1, because in TLS having thread id 0 can't
// be distinguished from not having a thread id at all (since NULL is
// defined as 0.)
int ThreadManager::last_id_ = 0;
Mutex* ThreadManager::mutex_ = OS::CreateMutex();
ThreadHandle ThreadManager::mutex_owner_(ThreadHandle::INVALID);
ThreadHandle ThreadManager::lazily_archived_thread_(ThreadHandle::INVALID);
ThreadState* ThreadManager::lazily_archived_thread_state_ = NULL;
void ThreadManager::ArchiveThread() {
ASSERT(!lazily_archived_thread_.IsValid());
ASSERT(!IsArchived());
ThreadState* state = ThreadState::GetFree();
state->Unlink();
Thread::SetThreadLocal(thread_state_key, reinterpret_cast<void*>(state));
lazily_archived_thread_.Initialize(ThreadHandle::SELF);
lazily_archived_thread_state_ = state;
ASSERT(state->id() == kInvalidId);
state->set_id(CurrentId());
ASSERT(state->id() != kInvalidId);
}
void ThreadManager::EagerlyArchiveThread() {
ThreadState* state = lazily_archived_thread_state_;
state->LinkInto(ThreadState::IN_USE_LIST);
char* to = state->data();
// Ensure that data containing GC roots are archived first, and handle them
// in ThreadManager::Iterate(ObjectVisitor*).
to = HandleScopeImplementer::ArchiveThread(to);
to = Top::ArchiveThread(to);
to = Relocatable::ArchiveState(to);
#ifdef ENABLE_DEBUGGER_SUPPORT
to = Debug::ArchiveDebug(to);
#endif
to = StackGuard::ArchiveStackGuard(to);
to = RegExpStack::ArchiveStack(to);
to = Bootstrapper::ArchiveState(to);
lazily_archived_thread_.Initialize(ThreadHandle::INVALID);
lazily_archived_thread_state_ = NULL;
}
void ThreadManager::FreeThreadResources() {
HandleScopeImplementer::FreeThreadResources();
Top::FreeThreadResources();
#ifdef ENABLE_DEBUGGER_SUPPORT
Debug::FreeThreadResources();
#endif
StackGuard::FreeThreadResources();
RegExpStack::FreeThreadResources();
Bootstrapper::FreeThreadResources();
}
bool ThreadManager::IsArchived() {
return Thread::HasThreadLocal(thread_state_key);
}
void ThreadManager::Iterate(ObjectVisitor* v) {
// Expecting no threads during serialization/deserialization
for (ThreadState* state = ThreadState::FirstInUse();
state != NULL;
state = state->Next()) {
char* data = state->data();
data = HandleScopeImplementer::Iterate(v, data);
data = Top::Iterate(v, data);
data = Relocatable::Iterate(v, data);
}
}
void ThreadManager::IterateArchivedThreads(ThreadVisitor* v) {
for (ThreadState* state = ThreadState::FirstInUse();
state != NULL;
state = state->Next()) {
char* data = state->data();
data += HandleScopeImplementer::ArchiveSpacePerThread();
Top::IterateThread(v, data);
}
}
int ThreadManager::CurrentId() {
return Thread::GetThreadLocalInt(thread_id_key);
}
void ThreadManager::AssignId() {
if (!HasId()) {
ASSERT(Locker::IsLocked());
int thread_id = ++last_id_;
ASSERT(thread_id > 0); // see the comment near last_id_ definition.
Thread::SetThreadLocalInt(thread_id_key, thread_id);
Top::set_thread_id(thread_id);
}
}
bool ThreadManager::HasId() {
return Thread::HasThreadLocal(thread_id_key);
}
void ThreadManager::TerminateExecution(int thread_id) {
for (ThreadState* state = ThreadState::FirstInUse();
state != NULL;
state = state->Next()) {
if (thread_id == state->id()) {
state->set_terminate_on_restore(true);
}
}
}
// This is the ContextSwitcher singleton. There is at most a single thread
// running which delivers preemption events to V8 threads.
ContextSwitcher* ContextSwitcher::singleton_ = NULL;
ContextSwitcher::ContextSwitcher(int every_n_ms)
: keep_going_(true),
sleep_ms_(every_n_ms) {
}
// Set the scheduling interval of V8 threads. This function starts the
// ContextSwitcher thread if needed.
void ContextSwitcher::StartPreemption(int every_n_ms) {
ASSERT(Locker::IsLocked());
if (singleton_ == NULL) {
// If the ContextSwitcher thread is not running at the moment start it now.
singleton_ = new ContextSwitcher(every_n_ms);
singleton_->Start();
} else {
// ContextSwitcher thread is already running, so we just change the
// scheduling interval.
singleton_->sleep_ms_ = every_n_ms;
}
}
// Disable preemption of V8 threads. If multiple threads want to use V8 they
// must cooperatively schedule amongst them from this point on.
void ContextSwitcher::StopPreemption() {
ASSERT(Locker::IsLocked());
if (singleton_ != NULL) {
// The ContextSwitcher thread is running. We need to stop it and release
// its resources.
singleton_->keep_going_ = false;
singleton_->Join(); // Wait for the ContextSwitcher thread to exit.
// Thread has exited, now we can delete it.
delete(singleton_);
singleton_ = NULL;
}
}
// Main loop of the ContextSwitcher thread: Preempt the currently running V8
// thread at regular intervals.
void ContextSwitcher::Run() {
while (keep_going_) {
OS::Sleep(sleep_ms_);
StackGuard::Preempt();
}
}
// Acknowledge the preemption by the receiving thread.
void ContextSwitcher::PreemptionReceived() {
ASSERT(Locker::IsLocked());
// There is currently no accounting being done for this. But could be in the
// future, which is why we leave this in.
}
} // namespace internal
} // namespace v8