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/*
* Copyright (C) 2005, 2008, 2009, 2014 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#ifndef JSLock_h
#define JSLock_h
#include <mutex>
#include <thread>
#include <wtf/Assertions.h>
#include <wtf/Noncopyable.h>
#include <wtf/RefPtr.h>
#include <wtf/ThreadSafeRefCounted.h>
#include <wtf/WTFThreadData.h>
namespace JSC {
// To make it safe to use JavaScript on multiple threads, it is
// important to lock before doing anything that allocates a
// JavaScript data structure or that interacts with shared state
// such as the protect count hash table. The simplest way to lock
// is to create a local JSLockHolder object in the scope where the lock
// must be held and pass it the context that requires protection.
// The lock is recursive so nesting is ok. The JSLock
// object also acts as a convenience short-hand for running important
// initialization routines.
// To avoid deadlock, sometimes it is necessary to temporarily
// release the lock. Since it is recursive you actually have to
// release all locks held by your thread. This is safe to do if
// you are executing code that doesn't require the lock, and you
// reacquire the right number of locks at the end. You can do this
// by constructing a locally scoped JSLock::DropAllLocks object. The
// DropAllLocks object takes care to release the JSLock only if your
// thread acquired it to begin with.
class ExecState;
class VM;
// This class is used to protect the initialization of the legacy single
// shared VM.
class GlobalJSLock {
WTF_MAKE_NONCOPYABLE(GlobalJSLock);
public:
JS_EXPORT_PRIVATE GlobalJSLock();
JS_EXPORT_PRIVATE ~GlobalJSLock();
static void initialize();
private:
static std::mutex* s_sharedInstanceMutex;
};
class JSLockHolder {
public:
JS_EXPORT_PRIVATE JSLockHolder(VM*);
JS_EXPORT_PRIVATE JSLockHolder(VM&);
JS_EXPORT_PRIVATE JSLockHolder(ExecState*);
JS_EXPORT_PRIVATE ~JSLockHolder();
private:
void init();
RefPtr<VM> m_vm;
};
class JSLock : public ThreadSafeRefCounted<JSLock> {
WTF_MAKE_NONCOPYABLE(JSLock);
public:
JSLock(VM*);
JS_EXPORT_PRIVATE ~JSLock();
JS_EXPORT_PRIVATE void lock();
JS_EXPORT_PRIVATE void unlock();
static void lock(ExecState*);
static void unlock(ExecState*);
static void lock(VM&);
static void unlock(VM&);
VM* vm() { return m_vm; }
bool hasExclusiveThread() const { return m_hasExclusiveThread; }
std::thread::id exclusiveThread() const
{
ASSERT(m_hasExclusiveThread);
return m_ownerThreadID;
}
JS_EXPORT_PRIVATE void setExclusiveThread(std::thread::id);
JS_EXPORT_PRIVATE bool currentThreadIsHoldingLock();
void willDestroyVM(VM*);
class DropAllLocks {
WTF_MAKE_NONCOPYABLE(DropAllLocks);
public:
JS_EXPORT_PRIVATE DropAllLocks(ExecState*);
JS_EXPORT_PRIVATE DropAllLocks(VM*);
JS_EXPORT_PRIVATE DropAllLocks(VM&);
JS_EXPORT_PRIVATE ~DropAllLocks();
void setDropDepth(unsigned depth) { m_dropDepth = depth; }
unsigned dropDepth() const { return m_dropDepth; }
private:
intptr_t m_droppedLockCount;
RefPtr<VM> m_vm;
unsigned m_dropDepth;
};
private:
void lock(intptr_t lockCount);
void unlock(intptr_t unlockCount);
void didAcquireLock();
void willReleaseLock();
unsigned dropAllLocks(DropAllLocks*);
void grabAllLocks(DropAllLocks*, unsigned lockCount);
std::mutex m_lock;
std::thread::id m_ownerThreadID;
intptr_t m_lockCount;
unsigned m_lockDropDepth;
bool m_hasExclusiveThread;
VM* m_vm;
AtomicStringTable* m_entryAtomicStringTable;
};
} // namespace
#endif // JSLock_h
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