14035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin/* Copyright (c) 2015, The Linux Foundation. All rights reserved. 24035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * 34035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * Redistribution and use in source and binary forms, with or without 44035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * modification, are permitted provided that the following conditions are 54035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * met: 64035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * * Redistributions of source code must retain the above copyright 74035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * notice, this list of conditions and the following disclaimer. 84035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * * Redistributions in binary form must reproduce the above 94035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * copyright notice, this list of conditions and the following 104035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * disclaimer in the documentation and/or other materials provided 114035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * with the distribution. 124035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * * Neither the name of The Linux Foundation, nor the names of its 134035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * contributors may be used to endorse or promote products derived 144035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * from this software without specific prior written permission. 154035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * 164035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED 174035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 184035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT 194035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS 204035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 214035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 224035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 234035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 244035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 254035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN 264035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 274035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin * 284035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin */ 294035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin#ifndef __LOC_SHARED_LOCK__ 304035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin#define __LOC_SHARED_LOCK__ 314035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin 324035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin#include <stddef.h> 3360c72c0a4cec04c4a85255c6965d6493337b3c80Kevin Tang#include <cutils/atomic.h> 344035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin#include <pthread.h> 354035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin 364035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// This is a utility created for use cases such that there are more than 374035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// one client who need to share the same lock, but it is not predictable 384035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// which of these clients is to last to go away. This shared lock deletes 394035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// itself when the last client calls its drop() method. To add a cient, 404035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// this share lock's share() method has to be called, so that the obj 414035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin// can maintain an accurate client count. 424035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjinclass LocSharedLock { 4360c72c0a4cec04c4a85255c6965d6493337b3c80Kevin Tang volatile int32_t mRef; 444035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin pthread_mutex_t mMutex; 454035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin inline ~LocSharedLock() { pthread_mutex_destroy(&mMutex); } 464035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjinpublic: 474035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin // first client to create this LockSharedLock 484035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin inline LocSharedLock() : mRef(1) { pthread_mutex_init(&mMutex, NULL); } 494035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin // following client(s) are to *share()* this lock created by the first client 5060c72c0a4cec04c4a85255c6965d6493337b3c80Kevin Tang inline LocSharedLock* share() { android_atomic_inc(&mRef); return this; } 514035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin // whe a client no longer needs this shared lock, drop() shall be called. 5260c72c0a4cec04c4a85255c6965d6493337b3c80Kevin Tang inline void drop() { if (1 == android_atomic_dec(&mRef)) delete this; } 534035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin // locking the lock to enter critical section 544035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin inline void lock() { pthread_mutex_lock(&mMutex); } 554035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin // unlocking the lock to leave the critical section 564035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin inline void unlock() { pthread_mutex_unlock(&mMutex); } 574035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin}; 584035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin 594035be28a255eaa5605dbd9abeb2340db584249cPatrick Tjin#endif //__LOC_SHARED_LOCK__ 60