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      1 /*
      2  * Copyright (C) 2011 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef ThreadRestrictionVerifier_h
     32 #define ThreadRestrictionVerifier_h
     33 
     34 #include "wtf/Assertions.h"
     35 #include "wtf/Threading.h"
     36 #include "wtf/ThreadingPrimitives.h"
     37 
     38 #if HAVE(DISPATCH_H)
     39 #include <dispatch/dispatch.h>
     40 #endif
     41 
     42 #ifndef NDEBUG
     43 
     44 namespace WTF {
     45 
     46 // Verifies that a class is used in a way that respects its lack of thread-safety.
     47 // The default mode is to verify that the object will only be used on a single thread. The
     48 // thread gets captured when setShared(true) is called.
     49 // The mode may be changed by calling useMutexMode (or turnOffVerification).
     50 class ThreadRestrictionVerifier {
     51 public:
     52     ThreadRestrictionVerifier()
     53         : m_mode(SingleThreadVerificationMode)
     54         , m_shared(false)
     55         , m_owningThread(0)
     56         , m_mutex(0)
     57 #if HAVE(DISPATCH_H)
     58         , m_owningQueue(0)
     59 #endif
     60     {
     61     }
     62 
     63 #if HAVE(DISPATCH_H)
     64     ~ThreadRestrictionVerifier()
     65     {
     66         if (m_owningQueue)
     67             dispatch_release(m_owningQueue);
     68     }
     69 #endif
     70 
     71     void setMutexMode(Mutex& mutex)
     72     {
     73         m_mode = MutexVerificationMode;
     74         m_mutex = &mutex;
     75     }
     76 
     77 #if HAVE(DISPATCH_H)
     78     void setDispatchQueueMode(dispatch_queue_t queue)
     79     {
     80         m_mode = SingleDispatchQueueVerificationMode;
     81         m_owningQueue = queue;
     82         dispatch_retain(m_owningQueue);
     83     }
     84 #endif
     85 
     86     void turnOffVerification()
     87     {
     88         m_mode = NoVerificationMode;
     89     }
     90 
     91     // Indicates that the object may (or may not) be owned by more than one place.
     92     void setShared(bool shared)
     93     {
     94 #if !ASSERT_DISABLED
     95         bool previouslyShared = m_shared;
     96 #endif
     97         m_shared = shared;
     98 
     99         if (!m_shared)
    100             return;
    101 
    102         switch (m_mode) {
    103         case SingleThreadVerificationMode:
    104             ASSERT(shared != previouslyShared);
    105             // Capture the current thread to verify that subsequent ref/deref happen on this thread.
    106             m_owningThread = currentThread();
    107             return;
    108 
    109 #if HAVE(DISPATCH_H)
    110         case SingleDispatchQueueVerificationMode:
    111 #endif
    112         case MutexVerificationMode:
    113         case NoVerificationMode:
    114             return;
    115         }
    116         ASSERT_NOT_REACHED();
    117     }
    118 
    119     // Is it OK to use the object at this moment on the current thread?
    120     bool isSafeToUse() const
    121     {
    122         if (!m_shared)
    123             return true;
    124 
    125         switch (m_mode) {
    126         case SingleThreadVerificationMode:
    127             return m_owningThread == currentThread();
    128 
    129         case MutexVerificationMode:
    130             if (!m_mutex->tryLock())
    131                 return true;
    132             m_mutex->unlock();
    133             return false;
    134 
    135 #if HAVE(DISPATCH_H)
    136         case SingleDispatchQueueVerificationMode:
    137             return m_owningQueue == dispatch_get_current_queue();
    138 #endif
    139 
    140         case NoVerificationMode:
    141             return true;
    142         }
    143         ASSERT_NOT_REACHED();
    144         return true;
    145     }
    146 
    147 private:
    148     enum VerificationMode {
    149         SingleThreadVerificationMode,
    150         MutexVerificationMode,
    151         NoVerificationMode,
    152 #if HAVE(DISPATCH_H)
    153         SingleDispatchQueueVerificationMode,
    154 #endif
    155     };
    156 
    157     VerificationMode m_mode;
    158     bool m_shared;
    159 
    160     // Used by SingleThreadVerificationMode
    161     ThreadIdentifier m_owningThread;
    162 
    163     // Used by MutexVerificationMode.
    164     Mutex* m_mutex;
    165 
    166 #if HAVE(DISPATCH_H)
    167     // Used by SingleDispatchQueueVerificationMode.
    168     dispatch_queue_t m_owningQueue;
    169 #endif
    170 };
    171 
    172 }
    173 
    174 #endif
    175 #endif
    176