50 lines
1.7 KiB
C
50 lines
1.7 KiB
C
/*
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* rwlock.h
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*
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* This header file describes the "reader/writer lock" synchronization
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* construct. The type rwlock_t describes the full state of the lock
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* including the POSIX 1003.1c synchronization objects necessary.
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*
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* A reader/writer lock allows a thread to lock shared data either for shared
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* read access or exclusive write access.
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*
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* The rwl_init() and rwl_destroy() functions, respectively, allow you to
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* initialize/create and destroy/free the reader/writer lock.
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*/
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#include <pthread.h>
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/*
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* Structure describing a read-write lock.
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*/
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typedef struct rwlock_tag {
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pthread_mutex_t mutex;
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pthread_cond_t read; /* wait for read */
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pthread_cond_t write; /* wait for write */
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int valid; /* set when valid */
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int r_active; /* readers active */
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int w_active; /* writer active */
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int r_wait; /* readers waiting */
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int w_wait; /* writers waiting */
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} rwlock_t;
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#define RWLOCK_VALID 0xfacade
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/*
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* Support static initialization of barriers
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*/
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#define RWL_INITIALIZER \
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{PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, \
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PTHREAD_COND_INITIALIZER, RWLOCK_VALID, 0, 0, 0, 0}
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/*
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* Define read-write lock functions
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*/
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extern int rwl_init (rwlock_t *rwlock);
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extern int rwl_destroy (rwlock_t *rwlock);
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extern int rwl_readlock (rwlock_t *rwlock);
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extern int rwl_readtrylock (rwlock_t *rwlock);
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extern int rwl_readunlock (rwlock_t *rwlock);
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extern int rwl_writelock (rwlock_t *rwlock);
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extern int rwl_writetrylock (rwlock_t *rwlock);
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extern int rwl_writeunlock (rwlock_t *rwlock);
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