author | Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com> |
Mon, 04 Oct 2010 01:32:07 +0300 | |
changeset 2 | 303757a437d3 |
parent 0 | 4f2f89ce4247 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (C) 2005, 2008, 2009 Apple Inc. All rights reserved. |
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* |
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* This library is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Library General Public |
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* License as published by the Free Software Foundation; either |
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* version 2 of the License, or (at your option) any later version. |
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* |
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* This library is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Library General Public License for more details. |
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* |
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* You should have received a copy of the GNU Library General Public License |
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* along with this library; see the file COPYING.LIB. If not, write to |
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* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, |
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* Boston, MA 02110-1301, USA. |
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* |
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*/ |
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#ifndef JSLock_h |
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#define JSLock_h |
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#include <wtf/Assertions.h> |
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#include <wtf/Noncopyable.h> |
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namespace JSC { |
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// To make it safe to use JavaScript on multiple threads, it is |
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// important to lock before doing anything that allocates a |
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// JavaScript data structure or that interacts with shared state |
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// such as the protect count hash table. The simplest way to lock |
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// is to create a local JSLock object in the scope where the lock |
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// must be held. The lock is recursive so nesting is ok. The JSLock |
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// object also acts as a convenience short-hand for running important |
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// initialization routines. |
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// To avoid deadlock, sometimes it is necessary to temporarily |
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// release the lock. Since it is recursive you actually have to |
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// release all locks held by your thread. This is safe to do if |
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// you are executing code that doesn't require the lock, and you |
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// reacquire the right number of locks at the end. You can do this |
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// by constructing a locally scoped JSLock::DropAllLocks object. The |
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// DropAllLocks object takes care to release the JSLock only if your |
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// thread acquired it to begin with. |
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// For contexts other than the single shared one, implicit locking is not done, |
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// but we still need to perform all the counting in order to keep debug |
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// assertions working, so that clients that use the shared context don't break. |
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class ExecState; |
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enum JSLockBehavior { SilenceAssertionsOnly, LockForReal }; |
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class JSLock : public Noncopyable { |
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public: |
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JSLock(ExecState*); |
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JSLock(JSLockBehavior lockBehavior) |
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: m_lockBehavior(lockBehavior) |
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{ |
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#ifdef NDEBUG |
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// Locking "not for real" is a debug-only feature. |
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if (lockBehavior == SilenceAssertionsOnly) |
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return; |
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#endif |
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lock(lockBehavior); |
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} |
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~JSLock() |
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{ |
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#ifdef NDEBUG |
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// Locking "not for real" is a debug-only feature. |
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if (m_lockBehavior == SilenceAssertionsOnly) |
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return; |
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#endif |
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unlock(m_lockBehavior); |
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} |
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static void lock(JSLockBehavior); |
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static void unlock(JSLockBehavior); |
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static void lock(ExecState*); |
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static void unlock(ExecState*); |
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static intptr_t lockCount(); |
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static bool currentThreadIsHoldingLock(); |
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JSLockBehavior m_lockBehavior; |
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class DropAllLocks : public Noncopyable { |
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public: |
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DropAllLocks(ExecState* exec); |
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DropAllLocks(JSLockBehavior); |
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~DropAllLocks(); |
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private: |
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intptr_t m_lockCount; |
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JSLockBehavior m_lockBehavior; |
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}; |
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}; |
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} // namespace |
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Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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#endif // JSLock_h |