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/*************************************************************************** |
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* * |
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* Copyright (C) 2006 Andreas Persson * |
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* * |
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* This program is free software; you can redistribute it and/or modify * |
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* it under the terms of the GNU General Public License as published by * |
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* the Free Software Foundation; either version 2 of the License, or * |
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* (at your option) any later version. * |
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* * |
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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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* * |
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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., 51 Franklin St, Fifth Floor, Boston, * |
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* MA 02110-1301 USA * |
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***************************************************************************/ |
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|
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#ifndef __SYNCHRONIZEDCONFIG_H__ |
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#define __SYNCHRONIZEDCONFIG_H__ |
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|
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#include "atomic.h" |
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|
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namespace LinuxSampler { |
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|
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/** |
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* Thread safe management of configuration data, where the data is |
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* updated by a single non real time thread and read by a single |
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* real time thread. |
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* |
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* The synchronization is achieved by using two instances of the |
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* configuration data. The non real time thread gets access to the |
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* instance not currently in use by the real time thread by |
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* calling GetConfigForUpdate(). After the data is updated, the |
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* non real time thread must call SwitchConfig() and redo the |
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* update on the other instance. SwitchConfig() blocks until it is |
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* safe to modify the other instance. |
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* |
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* The real time thread calls Lock() to get access to the data, |
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* and Unlock() when it is finished reading the data. (Neither |
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* Lock nor Unlock will block the real time thread, or use any |
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* system calls.) |
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*/ |
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template<class T> |
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class SynchronizedConfig { |
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public: |
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SynchronizedConfig(); |
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|
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// methods for the real time thread |
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|
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/** |
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* Gets the configuration object for use by the real time |
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* thread. The object is safe to use (read only) until |
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* Unlock() is called. |
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* |
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* @returns a reference to the configuration object to be |
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* read by the real time thread |
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*/ |
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const T& Lock() { |
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atomic_set(&lock, 1); |
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return config[atomic_read(&indexAtomic)]; |
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} |
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|
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/** |
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* Unlock the configuration object. Unlock() must be |
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* called by the real time thread after it has finished |
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* reading the configuration object. If the non real time |
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* thread is waiting in SwitchConfig() it will be awaken. |
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*/ |
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void Unlock() { |
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atomic_set(&lock, 0); |
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} |
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|
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|
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// methods for the non real time thread |
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|
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/** |
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* Gets the configuration object for use by the non real |
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* time thread. The object returned is not in use by the |
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* real time thread, so it can safely be updated. After |
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* the update is done, the non real time thread must call |
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* SwitchConfig() and the same update must be done again. |
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* |
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* @returns a reference to the configuration object to be |
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* updated by the non real time thread |
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*/ |
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T& GetConfigForUpdate(); |
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|
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/** |
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* Atomically switch the newly updated configuration |
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* object with the one used by the real time thread, then |
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* wait for the real time thread to finish working with |
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* the old object before returning the old object. |
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* SwitchConfig() must be called by the non real time |
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* thread after an update has been done, and the object |
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* returned must be updated in the same way as the first. |
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* |
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* @returns a reference to the configuration object to be |
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* updated by the non real time thread |
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*/ |
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T& SwitchConfig(); |
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|
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private: |
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atomic_t lock; |
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atomic_t indexAtomic; |
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int updateIndex; |
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T config[2]; |
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}; |
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|
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template<class T> SynchronizedConfig<T>::SynchronizedConfig() { |
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atomic_set(&lock, 0); |
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atomic_set(&indexAtomic, 0); |
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} |
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|
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template<class T> T& SynchronizedConfig<T>::GetConfigForUpdate() { |
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updateIndex = atomic_read(&indexAtomic) ^ 1; |
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return config[updateIndex]; |
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} |
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|
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template<class T> T& SynchronizedConfig<T>::SwitchConfig() { |
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atomic_set(&indexAtomic, updateIndex); |
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while (atomic_read(&lock)) |
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usleep(50000); |
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return config[updateIndex ^ 1]; |
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} |
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|
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} // namespace LinuxSampler |
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|
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#endif |