Ichthyostega
08cae2617d
explanation: we use pthread_once to define a mutex type descriptor, used to define some of our mutexes as recursive mutexes. Now, pthread_once relies on a counter stored in a given location; we used a non-exported global var for this counter. Unfortunately this ties the mutex initialisation to the static initialisation of the compilation unit holding this counter variable. Theoretically it would be possible (we never observed such an incident) that, during static initialisation, a singleton was brought up, which requires a class-scoped lock, implemented as recursive mutex. And it would be possible for this singleton locking to happen prior to initialisation of the mentioned counter variable. As a fix, I've moved the counter varialbe into a function scoped static variable, since that is guaranteed by the C++ runtime system to be initialised at first usage of the function, irrespective of the initialisation order of the enclosing compilation units
72 lines
1.9 KiB
C++
72 lines
1.9 KiB
C++
/*
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Sync - generic helper for object based locking and synchronisation
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Copyright (C) Lumiera.org
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2011, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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* *****************************************************/
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/** @file sync.cpp
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** This compilation unit holds the static attribute struct
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** for initialising pthread's recursive mutex.
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**
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*/
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#include "lib/sync.hpp"
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namespace lib {
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namespace sync {
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namespace { // private pthread attributes
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pthread_mutexattr_t attribute_;
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void
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initAttribute()
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{
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pthread_mutexattr_init (&attribute_);
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pthread_mutexattr_settype (&attribute_, PTHREAD_MUTEX_RECURSIVE);
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}
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inline pthread_mutexattr_t*
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recursive_flag()
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{
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static pthread_once_t _is_init_sync_mutex_attribute_(PTHREAD_ONCE_INIT);
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pthread_once (&_is_init_sync_mutex_attribute_, initAttribute);
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return &attribute_;
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}
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}
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/**
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* @internal creating a recursive mutex.
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* Defined here in a separate compilation unit,
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* so it can refer to a single mutex attribute flag.
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*/
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Wrapped_RecursiveMutex::Wrapped_RecursiveMutex()
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{
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pthread_mutex_init (&mutex_, recursive_flag());
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}
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}}// lib::sync
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