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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #ifndef threading_Mutex_h
       8             : #define threading_Mutex_h
       9             : 
      10             : #include "mozilla/Assertions.h"
      11             : #include "mozilla/Move.h"
      12             : #include "mozilla/PlatformMutex.h"
      13             : #include "mozilla/ThreadLocal.h"
      14             : #include "mozilla/Vector.h"
      15             : 
      16             : namespace js {
      17             : 
      18             : // A MutexId secifies the name and mutex order for a mutex.
      19             : //
      20             : // The mutex order defines the allowed order of mutex acqusition on a single
      21             : // thread. Mutexes must be acquired in strictly increasing order. Mutexes with
      22             : // the same order may not be held at the same time by that thread.
      23             : struct MutexId
      24             : {
      25             :   const char* name;
      26             :   uint32_t order;
      27             : };
      28             : 
      29             : #ifndef DEBUG
      30             : 
      31             : class Mutex : public mozilla::detail::MutexImpl
      32             : {
      33             : public:
      34             :   static bool Init() { return true; }
      35             :   static void ShutDown() {}
      36             : 
      37             :   explicit Mutex(const MutexId& id) {}
      38             : 
      39             :   using MutexImpl::lock;
      40             :   using MutexImpl::unlock;
      41             : };
      42             : 
      43             : #else
      44             : 
      45             : // In debug builds, js::Mutex is a wrapper over MutexImpl that checks correct
      46             : // locking order is observed.
      47             : //
      48             : // The class maintains a per-thread stack of currently-held mutexes to enable it
      49             : // to check this.
      50           0 : class Mutex : public mozilla::detail::MutexImpl
      51             : {
      52             : public:
      53             :   static bool Init();
      54             :   static void ShutDown();
      55             : 
      56          95 :   explicit Mutex(const MutexId& id)
      57          95 :    : id_(id)
      58             :   {
      59          95 :     MOZ_ASSERT(id_.order != 0);
      60          95 :   }
      61             : 
      62             :   void lock();
      63             :   void unlock();
      64             :   bool ownedByCurrentThread() const;
      65             : 
      66             : private:
      67             :   const MutexId id_;
      68             : 
      69             :   using MutexVector = mozilla::Vector<const Mutex*>;
      70             :   static MOZ_THREAD_LOCAL(MutexVector*) HeldMutexStack;
      71             :   static MutexVector& heldMutexStack();
      72             : };
      73             : 
      74             : #endif
      75             : 
      76             : } // namespace js
      77             : 
      78             : #endif // threading_Mutex_h