linux进程同步.doc

包括我自己在内，很多人对内核，进程，线程同步都不是很清楚，下面稍微总结一下：内核同步：主要是防止多核处理器同时访问修改某段代码，或者在对设备驱动程序进行临界区保护。主要有一下几种方式：1. Mutex（互斥）头文件：#include初始化方法：DEFINE_MUTEX(name);或者voidmutex_init(structmutex*lock);使用方法：voidmutex_lock(structmutex*lock);尝试得到互斥量，否则进入睡眠，不能被中断，否则会导致进程无法杀死intmutex_lock_interruptible(structmutex*lock);Same,butcanbeinterrupted.Ifinterrupted,returnsanonzerovalueanddoesntholdthelock.Testthereturnvalue!可以被中断intmutex_trylock(structmutex*lock);Neverwaits.Rmutex_is_locked(structmutex*lock);Justtellswhetherthemutexislockedornot.无等待voidmutex_unlock(structmutex*lock);Releasesthelock.Makesureyoudoitasquicklyaspossible!2. Reader/writer semphopres 读写信号量Allowsharedaccessbyunlimitedreaders,orbyonly1writer.Writersgetpriority.允许有限数量的读访问，但是只能有一个写访问。voidinit_rwsem(structrw_semaphore*sem);voiddown_read(structrw_semaphore*sem);intdown_read_trylock(structrw_semaphore*sem);intup_read(structrw_semaphore*sem);voiddown_write(structrw_semaphore*sem);intdown_write_trylock(structrw_semaphore*sem);intup_write(structrw_semaphore*sem);Wellsuitedforrarewrites,holdingthesemaphorebriefly.Otherwise,readersgetstarved,waitingtoolongforthesemaphoretobereleased.3. Spinlocks 自旋锁初始化：Staticspinlock_tmy_lock=SPIN_LOCK_UNLOCKED;Dynamicvoidspin_lock_init(spinlock_t*lock);使用：voidspin_unlock(spinlock_t*lock);Doesntdisableinterrupts.Usedforlockinginprocesscontext (criticalsectionsinwhichyoudonotwanttosleep).voidspin_lock_irqsave/spin_unlock_irqrestore(spinlock_t*lock,unsignedlongflags);Disables/restoresIRQsonthelocalCPU.Typicallyusedwhenthelockcanbeaccessedinbothprocessandinterruptcontext,topreventpreemptionbyinterrupts进程同步/通信1. Semaphore 信号量简单过程：semaphore sv = 1; loop forever P(sv); critical code section; V(sv); noncritical code section;头文件以及函数：#include int semctl(int sem_id, int sem_num, int command, .);int semget(key_t key, int num_sems, int sem_flags);int semop(int sem_id, struct sembuf *sem_ops, size_t num_sem_ops);2.Share Memory 共享内存头文件以及函数#include void *shmat(int shm_id, const void *shm_addr, int shmflg);int shmctl(int shm_id, int cmd, struct shmid_ds *buf);int shmdt(const void *shm_addr);int shmget(key_t key, size_t size, int shmflg);3.Message Queues 消息队列头文件以及函数#include int msgctl(int msqid, int cmd, struct msqid_ds *buf);int msgget(key_t key, int msgflg);int msgrcv(int msqid, void *msg_ptr, size_t msg_sz, long int msgtype, int msgflg);int msgsnd(int msqid, const void *msg_ptr, size_t msg_sz, int msgflg);线程同步1. semophore 信号量简单用法：#include sem_t bin_sem; res = sem_init(&bin_sem, 0, 0);sem_wait(&bin_sem);sem_post(&bin_sem);sem_destroy(&bin_sem);2. Mutex 互斥头文件以及函数#include int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutexattr);int pthread_mutex_lock(pthread_mutex_t *mutex);int pthread_mutex_unlock(pthread_mutex_t *mutex);int pthread_mutex_destroy(pthread_mutex_t *mutex);3. 读写锁头文件以及函数#includeintpthread_rwlock_init(pthread_rwlock_t*restrict rwlock,constpthread_rwlockattr_t*restrict attr);intpthread_rwlock_destroy(pthread_rwlock_t*rwlock);intpthread_rwlock_rdlock(pthread_rwlock_t*rwlock);intpthread_rwlock_wrlock(pthread_rwlock_t*rwlock);intpthread_rwlock_unlock(pthread_rwlock_t*rwlock);intpthread_rwlock_tryrdlock(pthread_rwlock_t*rwlock);intpthread_rwlock_trywrlock(pthread_rwlock_t*rwlock);4. 条件变量#include pthread_cond_t cond = PTHREAD_COND_INITIALIZER;int pthread_cond_init(pthread_cond_t *cond, pthread_condattr_t*cond_attr);int pthread_cond_signal(pthread_cond_t *cond);int pthread_cond_broadcast(pthread_cond_t *cond);int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);int pthread_cond_timedwait(pthread_cond_t *cond