#include "config.h"
#include "JSLock.h"
#include "Heap.h"
#include "CallFrame.h"
#include "JSGlobalObject.h"
#include "JSObject.h"
#include "JSCInlines.h"
#include "MachineStackMarker.h"
#include "SamplingProfiler.h"
#include "WasmMachineThreads.h"
#include <thread>
#include <wtf/Threading.h>
#include <wtf/threads/Signals.h>
namespace JSC {
Lock GlobalJSLock::s_sharedInstanceMutex;
GlobalJSLock::GlobalJSLock()
{
s_sharedInstanceMutex.lock();
}
GlobalJSLock::~GlobalJSLock()
{
s_sharedInstanceMutex.unlock();
}
JSLockHolder::JSLockHolder(ExecState* exec)
: m_vm(&exec->vm())
{
init();
}
JSLockHolder::JSLockHolder(VM* vm)
: m_vm(vm)
{
init();
}
JSLockHolder::JSLockHolder(VM& vm)
: m_vm(&vm)
{
init();
}
void JSLockHolder::init()
{
m_vm->apiLock().lock();
}
JSLockHolder::~JSLockHolder()
{
RefPtr<JSLock> apiLock(&m_vm->apiLock());
m_vm = nullptr;
apiLock->unlock();
}
JSLock::JSLock(VM* vm)
: m_lockCount(0)
, m_lockDropDepth(0)
, m_vm(vm)
, m_entryAtomicStringTable(nullptr)
{
}
JSLock::~JSLock()
{
}
void JSLock::willDestroyVM(VM* vm)
{
ASSERT_UNUSED(vm, m_vm == vm);
m_vm = nullptr;
}
void JSLock::lock()
{
lock(1);
}
void JSLock::lock(intptr_t lockCount)
{
ASSERT(lockCount > 0);
bool success = m_lock.tryLock();
if (UNLIKELY(!success)) {
if (currentThreadIsHoldingLock()) {
m_lockCount += lockCount;
return;
}
m_lock.lock();
}
m_ownerThread = &Thread::current();
WTF::storeStoreFence();
m_hasOwnerThread = true;
ASSERT(!m_lockCount);
m_lockCount = lockCount;
didAcquireLock();
}
void JSLock::didAcquireLock()
{
WTF::speculationFence();
if (!m_vm)
return;
Thread& thread = Thread::current();
ASSERT(!m_entryAtomicStringTable);
m_entryAtomicStringTable = thread.setCurrentAtomicStringTable(m_vm->atomicStringTable());
ASSERT(m_entryAtomicStringTable);
m_vm->setLastStackTop(thread.savedLastStackTop());
ASSERT(thread.stack().contains(m_vm->lastStackTop()));
if (m_vm->heap.hasAccess())
m_shouldReleaseHeapAccess = false;
else {
m_vm->heap.acquireAccess();
m_shouldReleaseHeapAccess = true;
}
RELEASE_ASSERT(!m_vm->stackPointerAtVMEntry());
void* p = &p; m_vm->setStackPointerAtVMEntry(p);
m_vm->heap.machineThreads().addCurrentThread();
#if ENABLE(WEBASSEMBLY)
Wasm::startTrackingCurrentThread();
#endif
#if HAVE(MACH_EXCEPTIONS)
registerThreadForMachExceptionHandling(Thread::current());
#endif
m_vm->traps().notifyGrabAllLocks();
m_vm->firePrimitiveGigacageEnabledIfNecessary();
#if ENABLE(SAMPLING_PROFILER)
if (SamplingProfiler* samplingProfiler = m_vm->samplingProfiler())
samplingProfiler->noticeJSLockAcquisition();
#endif
}
void JSLock::unlock()
{
unlock(1);
}
void JSLock::unlock(intptr_t unlockCount)
{
RELEASE_ASSERT(currentThreadIsHoldingLock());
ASSERT(m_lockCount >= unlockCount);
if (unlockCount == m_lockCount)
willReleaseLock();
m_lockCount -= unlockCount;
if (!m_lockCount) {
m_hasOwnerThread = false;
m_lock.unlock();
}
}
void JSLock::willReleaseLock()
{
WTF::speculationFence();
RefPtr<VM> vm = m_vm;
if (vm) {
vm->drainMicrotasks();
if (!vm->topCallFrame)
vm->clearLastException();
vm->heap.releaseDelayedReleasedObjects();
vm->setStackPointerAtVMEntry(nullptr);
if (m_shouldReleaseHeapAccess)
vm->heap.releaseAccess();
}
if (m_entryAtomicStringTable) {
Thread::current().setCurrentAtomicStringTable(m_entryAtomicStringTable);
m_entryAtomicStringTable = nullptr;
}
}
void JSLock::lock(ExecState* exec)
{
exec->vm().apiLock().lock();
}
void JSLock::unlock(ExecState* exec)
{
exec->vm().apiLock().unlock();
}
unsigned JSLock::dropAllLocks(DropAllLocks* dropper)
{
if (!currentThreadIsHoldingLock())
return 0;
++m_lockDropDepth;
dropper->setDropDepth(m_lockDropDepth);
Thread& thread = Thread::current();
thread.setSavedStackPointerAtVMEntry(m_vm->stackPointerAtVMEntry());
thread.setSavedLastStackTop(m_vm->lastStackTop());
unsigned droppedLockCount = m_lockCount;
unlock(droppedLockCount);
return droppedLockCount;
}
void JSLock::grabAllLocks(DropAllLocks* dropper, unsigned droppedLockCount)
{
if (!droppedLockCount)
return;
ASSERT(!currentThreadIsHoldingLock());
lock(droppedLockCount);
while (dropper->dropDepth() != m_lockDropDepth) {
unlock(droppedLockCount);
Thread::yield();
lock(droppedLockCount);
}
--m_lockDropDepth;
Thread& thread = Thread::current();
m_vm->setStackPointerAtVMEntry(thread.savedStackPointerAtVMEntry());
m_vm->setLastStackTop(thread.savedLastStackTop());
}
JSLock::DropAllLocks::DropAllLocks(VM* vm)
: m_droppedLockCount(0)
, m_vm(vm->refCount() ? vm : nullptr)
{
if (!m_vm)
return;
RELEASE_ASSERT(!m_vm->apiLock().currentThreadIsHoldingLock() || !m_vm->isCollectorBusyOnCurrentThread());
m_droppedLockCount = m_vm->apiLock().dropAllLocks(this);
}
JSLock::DropAllLocks::DropAllLocks(ExecState* exec)
: DropAllLocks(exec ? &exec->vm() : nullptr)
{
}
JSLock::DropAllLocks::DropAllLocks(VM& vm)
: DropAllLocks(&vm)
{
}
JSLock::DropAllLocks::~DropAllLocks()
{
if (!m_vm)
return;
m_vm->apiLock().grabAllLocks(this, m_droppedLockCount);
}
}