| /* |
| * Copyright (C) 2011 Google Inc. 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. |
| */ |
| |
| #ifndef ThreadRestrictionVerifier_h |
| #define ThreadRestrictionVerifier_h |
| |
| #include "wtf/Assertions.h" |
| |
| #if ENABLE(ASSERT) |
| |
| #include "wtf/Threading.h" |
| |
| namespace WTF { |
| |
| // Verifies that a class is used in a way that respects its lack of |
| // thread-safety. The default mode is to verify that the object will only be |
| // used on a single thread. The thread gets captured when setShared(true) is |
| // called. The mode may be changed by calling useMutexMode (or |
| // turnOffVerification). |
| class ThreadRestrictionVerifier { |
| public: |
| ThreadRestrictionVerifier() : m_shared(false), m_owningThread(0) {} |
| |
| void checkSafeToUse() const { |
| // If this assert fires, it either indicates a thread safety issue or |
| // that the verification needs to change. |
| ASSERT_WITH_SECURITY_IMPLICATION(isSafeToUse()); |
| } |
| |
| // Call onRef() before refCount is incremented in ref(). |
| void onRef(int refCount) { |
| // Start thread verification as soon as the ref count gets to 2. This |
| // heuristic reflects the fact that items are often created on one |
| // thread and then given to another thread to be used. |
| // FIXME: Make this restriction tigher. Especially as we move to more |
| // common methods for sharing items across threads like |
| // CrossThreadCopier.h |
| // We should be able to add a "detachFromThread" method to make this |
| // explicit. |
| if (refCount == 1) |
| setShared(true); |
| checkSafeToUse(); |
| } |
| |
| // Call onDeref() before refCount is decremented in deref(). |
| void onDeref(int refCount) { |
| checkSafeToUse(); |
| |
| // Stop thread verification when the ref goes to 1 because it |
| // is safe to be passed to another thread at this point. |
| if (refCount == 2) |
| setShared(false); |
| } |
| |
| private: |
| // Indicates that the object may (or may not) be owned by more than one place. |
| void setShared(bool shared) { |
| bool previouslyShared = m_shared; |
| m_shared = shared; |
| |
| if (!m_shared) |
| return; |
| |
| ASSERT_UNUSED(previouslyShared, shared != previouslyShared); |
| // Capture the current thread to verify that subsequent ref/deref happen on |
| // this thread. |
| m_owningThread = currentThread(); |
| } |
| |
| // Is it OK to use the object at this moment on the current thread? |
| bool isSafeToUse() const { |
| if (!m_shared) |
| return true; |
| |
| return m_owningThread == currentThread(); |
| } |
| |
| bool m_shared; |
| |
| ThreadIdentifier m_owningThread; |
| }; |
| |
| } // namespace WTF |
| |
| #endif // ENABLE(ASSERT) |
| #endif // ThreadRestrictionVerifier_h |