text: /*
      Copyright 2005-2015 Intel Corporation.  All Rights Reserved.
  
      This file is part of Threading Building Blocks. Threading Building Blocks is free software;
      you can redistribute it and/or modify it under the terms of the GNU General Public License
      version 2  as  published  by  the  Free Software Foundation.  Threading Building Blocks 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 General Public License for more details.   You should have received a copy of
      the  GNU General Public License along with Threading Building Blocks; if not, write to the
      Free Software Foundation, Inc.,  51 Franklin St,  Fifth Floor,  Boston,  MA 02110-1301 USA
  
      As a special exception,  you may use this file  as part of a free software library without
      restriction.  Specifically,  if other files instantiate templates  or use macros or inline
      functions from this file, or you compile this file and link it with other files to produce
      an executable,  this file does not by itself cause the resulting executable to be covered
      by the GNU General Public License. This exception does not however invalidate any other
      reasons why the executable file might be covered by the GNU General Public License.
  */
  
  #ifndef __TBB_queuing_mutex_H
  #define __TBB_queuing_mutex_H
  
  #include "tbb_config.h"
  
  #if !TBB_USE_EXCEPTIONS && _MSC_VER
      // Suppress "C++ exception handler used, but unwind semantics are not enabled" warning in STL headers
      #pragma warning (push)
      #pragma warning (disable: 4530)
  #endif
  
  #include <cstring>
  
  #if !TBB_USE_EXCEPTIONS && _MSC_VER
      #pragma warning (pop)
  #endif
  
  #include "atomic.h"
  #include "tbb_profiling.h"
  
  namespace tbb {
  
  //! Queuing mutex with local-only spinning.
  /** @ingroup synchronization */
  class queuing_mutex : internal::mutex_copy_deprecated_and_disabled {
  public:
      //! Construct unacquired mutex.
      queuing_mutex() {
          q_tail = NULL;
  #if TBB_USE_THREADING_TOOLS
          internal_construct();
  #endif
      }
  
      //! The scoped locking pattern
      /** It helps to avoid the common problem of forgetting to release lock.
          It also nicely provides the "node" for queuing locks. */
      class scoped_lock: internal::no_copy {
          //! Initialize fields to mean "no lock held".
          void initialize() {
              mutex = NULL;
  #if TBB_USE_ASSERT
              internal::poison_pointer(next);
  #endif /* TBB_USE_ASSERT */
          }
  
      public:
          //! Construct lock that has not acquired a mutex.
          /** Equivalent to zero-initialization of *this. */
          scoped_lock() {initialize();}
  
          //! Acquire lock on given mutex.
          scoped_lock( queuing_mutex& m ) {
              initialize();
              acquire(m);
          }
  
          //! Release lock (if lock is held).
          ~scoped_lock() {
              if( mutex ) release();
          }
  
          //! Acquire lock on given mutex.
          void __TBB_EXPORTED_METHOD acquire( queuing_mutex& m );
  
          //! Acquire lock on given mutex if free (i.e. non-blocking)
          bool __TBB_EXPORTED_METHOD try_acquire( queuing_mutex& m );
  
          //! Release lock.
          void __TBB_EXPORTED_METHOD release();
  
      private:
          //! The pointer to the mutex owned, or NULL if not holding a mutex.
          queuing_mutex* mutex;
  
          //! The pointer to the next competitor for a mutex
          scoped_lock *next;
  
          //! The local spin-wait variable
          /** Inverted (0 - blocked, 1 - acquired the mutex) for the sake of
              zero-initialization.  Defining it as an entire word instead of
              a byte seems to help performance slightly. */
          uintptr_t going;
      };
  
      void __TBB_EXPORTED_METHOD internal_construct();
  
      // Mutex traits
      static const bool is_rw_mutex = false;
      static const bool is_recursive_mutex = false;
      static const bool is_fair_mutex = true;
  
  private:
      //! The last competitor requesting the lock
      atomic<scoped_lock*> q_tail;
  
  };
  
  __TBB_DEFINE_PROFILING_SET_NAME(queuing_mutex)
  
  } // namespace tbb
  
  #endif /* __TBB_queuing_mutex_H */
  