138 lines
3.2 KiB
C
138 lines
3.2 KiB
C
#include <minix/mthread.h>
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#include "global.h"
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/*===========================================================================*
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* mthread_rwlock_init *
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*===========================================================================*/
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int mthread_rwlock_init(rwlock)
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mthread_rwlock_t *rwlock; /* The rwlock to be initialized */
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{
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/* Initialize a readers/writer lock. */
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int r;
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if (!rwlock)
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return EINVAL;
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rwlock->writer = NO_THREAD;
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rwlock->readers = 0;
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r = mthread_mutex_init(&rwlock->queue, NULL);
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if (r != 0)
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return r;
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r = mthread_event_init(&rwlock->drain);
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if (r != 0)
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mthread_mutex_destroy(&rwlock->queue);
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return r;
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}
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/*===========================================================================*
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* mthread_rwlock_destroy *
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*===========================================================================*/
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int mthread_rwlock_destroy(rwlock)
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mthread_rwlock_t *rwlock; /* The rwlock to be destroyed */
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{
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/* Destroy a readers/writer lock. */
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int r;
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if (!rwlock)
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return EINVAL;
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assert(rwlock->writer == NO_THREAD);
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assert(rwlock->readers == 0);
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r = mthread_event_destroy(&rwlock->drain);
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if (r != 0)
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return r;
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return mthread_mutex_destroy(&rwlock->queue);
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}
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/*===========================================================================*
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* mthread_rwlock_rdlock *
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*===========================================================================*/
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int mthread_rwlock_rdlock(rwlock)
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mthread_rwlock_t *rwlock; /* The rwlock to be read locked */
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{
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/* Acquire a reader lock. */
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int r;
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if (!rwlock)
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return EINVAL;
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r = mthread_mutex_lock(&rwlock->queue);
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if (r != 0)
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return r;
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r = mthread_mutex_unlock(&rwlock->queue);
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if (r != 0)
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return r;
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rwlock->readers++;
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return 0;
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}
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/*===========================================================================*
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* mthread_rwlock_wrlock *
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*===========================================================================*/
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int mthread_rwlock_wrlock(rwlock)
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mthread_rwlock_t *rwlock; /* The rwlock to be write locked */
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{
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/* Acquire a writer lock. */
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int r;
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if (!rwlock)
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return EINVAL;
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r = mthread_mutex_lock(&rwlock->queue);
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if (r != 0)
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return r;
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rwlock->writer = current_thread;
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if (rwlock->readers > 0)
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r = mthread_event_wait(&rwlock->drain);
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if (r == 0)
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assert(rwlock->readers == 0);
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return r;
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}
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/*===========================================================================*
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* mthread_rwlock_unlock *
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*===========================================================================*/
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int mthread_rwlock_unlock(rwlock)
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mthread_rwlock_t *rwlock; /* The rwlock to be unlocked */
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{
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/* Release a lock. */
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int r;
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r = 0;
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if (!rwlock)
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return EINVAL;
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if (rwlock->writer == current_thread) {
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rwlock->writer = NO_THREAD;
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r = mthread_mutex_unlock(&rwlock->queue);
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} else {
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assert(rwlock->readers > 0);
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rwlock->readers--;
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if (rwlock->readers == 0 && rwlock->writer != NO_THREAD)
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r = mthread_event_fire(&rwlock->drain);
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}
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return r;
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}
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/* pthread compatibility layer. */
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__weak_alias(pthread_rwlock_destroy, mthread_rwlock_destroy)
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__weak_alias(pthread_rwlock_rdlock, mthread_rwlock_rdlock)
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__weak_alias(pthread_rwlock_wrlock, mthread_rwlock_wrlock)
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__weak_alias(pthread_rwlock_unlock, mthread_rwlock_unlock)
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