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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 {
// 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) {
// TODO(isolates): When Locker has Isolate parameter and it is provided, grab
// that one instead of using the current one.
// We pull default isolate for Locker constructor w/o p[arameter.
// A thread should not enter an isolate before acquiring a lock,
// in cases which mandate using Lockers.
// So getting a lock is the first thing threads do in a scenario where
// multple threads share an isolate. Hence, we need to access
// 'locking isolate' before we can actually enter into default isolate.
internal::Isolate* isolate = internal::Isolate::GetDefaultIsolateForLocking();
ASSERT(isolate != NULL);
// Record that the Locker has been used at least once.
active_ = true;
// Get the big lock if necessary.
if (!isolate->thread_manager()->IsLockedByCurrentThread()) {
isolate->thread_manager()->Lock();
has_lock_ = true;
if (isolate->IsDefaultIsolate()) {
// This only enters if not yet entered.
internal::Isolate::EnterDefaultIsolate();
}
ASSERT(internal::Thread::HasThreadLocal(
internal::Isolate::thread_id_key()));
// 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 (!isolate->IsInitialized()) {
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 (isolate->thread_manager()->RestoreThread()) {
top_level_ = false;
} else {
internal::ExecutionAccess access(isolate);
isolate->stack_guard()->ClearThread(access);
isolate->stack_guard()->InitThread(access);
}
}
ASSERT(isolate->thread_manager()->IsLockedByCurrentThread());
}
bool Locker::IsLocked() {
return internal::Isolate::Current()->thread_manager()->
IsLockedByCurrentThread();
}
Locker::~Locker() {
// TODO(isolate): this should use a field storing the isolate it
// locked instead.
internal::Isolate* isolate = internal::Isolate::Current();
ASSERT(isolate->thread_manager()->IsLockedByCurrentThread());
if (has_lock_) {
if (top_level_) {
isolate->thread_manager()->FreeThreadResources();
} else {
isolate->thread_manager()->ArchiveThread();
}
isolate->thread_manager()->Unlock();
}
}
Unlocker::Unlocker() {
internal::Isolate* isolate = internal::Isolate::Current();
ASSERT(isolate->thread_manager()->IsLockedByCurrentThread());
isolate->thread_manager()->ArchiveThread();
isolate->thread_manager()->Unlock();
}
Unlocker::~Unlocker() {
// TODO(isolates): check it's the isolate we unlocked.
internal::Isolate* isolate = internal::Isolate::Current();
ASSERT(!isolate->thread_manager()->IsLockedByCurrentThread());
isolate->thread_manager()->Lock();
isolate->thread_manager()->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_.Equals(ThreadId::Current())) {
lazily_archived_thread_ = ThreadId::Invalid();
ASSERT(Isolate::CurrentPerIsolateThreadData()->thread_state() ==
lazily_archived_thread_state_);
lazily_archived_thread_state_->set_id(ThreadId::Invalid());
lazily_archived_thread_state_->LinkInto(ThreadState::FREE_LIST);
lazily_archived_thread_state_ = NULL;
Isolate::CurrentPerIsolateThreadData()->set_thread_state(NULL);
return true;
}
// Make sure that the preemption thread cannot modify the thread state while
// it is being archived or restored.
ExecutionAccess access(isolate_);
// If there is another thread that was lazily archived then we have to really
// archive it now.
if (lazily_archived_thread_.IsValid()) {
EagerlyArchiveThread();
}
Isolate::PerIsolateThreadData* per_thread =
Isolate::CurrentPerIsolateThreadData();
if (per_thread == NULL || per_thread->thread_state() == NULL) {
// This is a new thread.
isolate_->stack_guard()->InitThread(access);
return false;
}
ThreadState* state = per_thread->thread_state();
char* from = state->data();
from = isolate_->handle_scope_implementer()->RestoreThread(from);
from = isolate_->RestoreThread(from);
from = Relocatable::RestoreState(from);
#ifdef ENABLE_DEBUGGER_SUPPORT
from = isolate_->debug()->RestoreDebug(from);
#endif
from = isolate_->stack_guard()->RestoreStackGuard(from);
from = isolate_->regexp_stack()->RestoreStack(from);
from = isolate_->bootstrapper()->RestoreState(from);
per_thread->set_thread_state(NULL);
if (state->terminate_on_restore()) {
isolate_->stack_guard()->TerminateExecution();
state->set_terminate_on_restore(false);
}
state->set_id(ThreadId::Invalid());
state->Unlink();
state->LinkInto(ThreadState::FREE_LIST);
return true;
}
void ThreadManager::Lock() {
mutex_->Lock();
mutex_owner_ = ThreadId::Current();
ASSERT(IsLockedByCurrentThread());
}
void ThreadManager::Unlock() {
mutex_owner_ = ThreadId::Invalid();
mutex_->Unlock();
}
static int ArchiveSpacePerThread() {
return HandleScopeImplementer::ArchiveSpacePerThread() +
Isolate::ArchiveSpacePerThread() +
#ifdef ENABLE_DEBUGGER_SUPPORT
Debug::ArchiveSpacePerThread() +
#endif
StackGuard::ArchiveSpacePerThread() +
RegExpStack::ArchiveSpacePerThread() +
Bootstrapper::ArchiveSpacePerThread() +
Relocatable::ArchiveSpacePerThread();
}
ThreadState::ThreadState(ThreadManager* thread_manager)
: id_(ThreadId::Invalid()),
terminate_on_restore_(false),
next_(this),
previous_(this),
thread_manager_(thread_manager) {
}
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 ? thread_manager_->free_anchor_
: thread_manager_->in_use_anchor_;
next_ = flying_anchor->next_;
previous_ = flying_anchor;
flying_anchor->next_ = this;
next_->previous_ = this;
}
ThreadState* ThreadManager::GetFreeThreadState() {
ThreadState* gotten = free_anchor_->next_;
if (gotten == free_anchor_) {
ThreadState* new_thread_state = new ThreadState(this);
new_thread_state->AllocateSpace();
return new_thread_state;
}
return gotten;
}
// Gets the first in the list of archived threads.
ThreadState* ThreadManager::FirstThreadStateInUse() {
return in_use_anchor_->Next();
}
ThreadState* ThreadState::Next() {
if (next_ == thread_manager_->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.)
ThreadManager::ThreadManager()
: mutex_(OS::CreateMutex()),
mutex_owner_(ThreadId::Invalid()),
lazily_archived_thread_(ThreadId::Invalid()),
lazily_archived_thread_state_(NULL),
free_anchor_(NULL),
in_use_anchor_(NULL) {
free_anchor_ = new ThreadState(this);
in_use_anchor_ = new ThreadState(this);
}
ThreadManager::~ThreadManager() {
// TODO(isolates): Destroy mutexes.
}
void ThreadManager::ArchiveThread() {
ASSERT(lazily_archived_thread_.Equals(ThreadId::Invalid()));
ASSERT(!IsArchived());
ThreadState* state = GetFreeThreadState();
state->Unlink();
Isolate::CurrentPerIsolateThreadData()->set_thread_state(state);
lazily_archived_thread_ = ThreadId::Current();
lazily_archived_thread_state_ = state;
ASSERT(state->id().Equals(ThreadId::Invalid()));
state->set_id(CurrentId());
ASSERT(!state->id().Equals(ThreadId::Invalid()));
}
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 = isolate_->handle_scope_implementer()->ArchiveThread(to);
to = isolate_->ArchiveThread(to);
to = Relocatable::ArchiveState(to);
#ifdef ENABLE_DEBUGGER_SUPPORT
to = isolate_->debug()->ArchiveDebug(to);
#endif
to = isolate_->stack_guard()->ArchiveStackGuard(to);
to = isolate_->regexp_stack()->ArchiveStack(to);
to = isolate_->bootstrapper()->ArchiveState(to);
lazily_archived_thread_ = ThreadId::Invalid();
lazily_archived_thread_state_ = NULL;
}
void ThreadManager::FreeThreadResources() {
isolate_->handle_scope_implementer()->FreeThreadResources();
isolate_->FreeThreadResources();
#ifdef ENABLE_DEBUGGER_SUPPORT
isolate_->debug()->FreeThreadResources();
#endif
isolate_->stack_guard()->FreeThreadResources();
isolate_->regexp_stack()->FreeThreadResources();
isolate_->bootstrapper()->FreeThreadResources();
}
bool ThreadManager::IsArchived() {
Isolate::PerIsolateThreadData* data = Isolate::CurrentPerIsolateThreadData();
return data != NULL && data->thread_state() != NULL;
}
void ThreadManager::Iterate(ObjectVisitor* v) {
// Expecting no threads during serialization/deserialization
for (ThreadState* state = FirstThreadStateInUse();
state != NULL;
state = state->Next()) {
char* data = state->data();
data = HandleScopeImplementer::Iterate(v, data);
data = isolate_->Iterate(v, data);
data = Relocatable::Iterate(v, data);
}
}
void ThreadManager::IterateArchivedThreads(ThreadVisitor* v) {
for (ThreadState* state = FirstThreadStateInUse();
state != NULL;
state = state->Next()) {
char* data = state->data();
data += HandleScopeImplementer::ArchiveSpacePerThread();
isolate_->IterateThread(v, data);
}
}
ThreadId ThreadManager::CurrentId() {
return ThreadId::Current();
}
void ThreadManager::TerminateExecution(ThreadId thread_id) {
for (ThreadState* state = FirstThreadStateInUse();
state != NULL;
state = state->Next()) {
if (thread_id.Equals(state->id())) {
state->set_terminate_on_restore(true);
}
}
}
ContextSwitcher::ContextSwitcher(Isolate* isolate, int every_n_ms)
: Thread(isolate, "v8:CtxtSwitcher"),
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) {
Isolate* isolate = Isolate::Current();
ASSERT(Locker::IsLocked());
if (isolate->context_switcher() == NULL) {
// If the ContextSwitcher thread is not running at the moment start it now.
isolate->set_context_switcher(new ContextSwitcher(isolate, every_n_ms));
isolate->context_switcher()->Start();
} else {
// ContextSwitcher thread is already running, so we just change the
// scheduling interval.
isolate->context_switcher()->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() {
Isolate* isolate = Isolate::Current();
ASSERT(Locker::IsLocked());
if (isolate->context_switcher() != NULL) {
// The ContextSwitcher thread is running. We need to stop it and release
// its resources.
isolate->context_switcher()->keep_going_ = false;
// Wait for the ContextSwitcher thread to exit.
isolate->context_switcher()->Join();
// Thread has exited, now we can delete it.
delete(isolate->context_switcher());
isolate->set_context_switcher(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_);
isolate()->stack_guard()->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