mirror of https://code.videolan.org/videolan/vlc
Read/write locks
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f3aaa6e2c2
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@ -107,6 +107,7 @@ typedef pthread_t vlc_thread_t;
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typedef pthread_mutex_t vlc_mutex_t;
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#define VLC_STATIC_MUTEX PTHREAD_MUTEX_INITIALIZER
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typedef pthread_cond_t vlc_cond_t;
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typedef pthread_rwlock_t vlc_rwlock_t;
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typedef pthread_key_t vlc_threadvar_t;
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typedef struct vlc_timer_t vlc_timer_t;
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@ -143,6 +144,17 @@ typedef struct
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#define VLC_STATIC_MUTEX { 0, }
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typedef HANDLE vlc_cond_t;
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typedef struct
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{
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vlc_mutex_t mutex;
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vlc_cond_t read_wait;
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vlc_cond_t write_wait;
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unsigned long readers;
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unsigned long writers;
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DWORD writer;
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} vlc_rwlock_t;
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typedef DWORD vlc_threadvar_t;
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typedef struct vlc_timer_t vlc_timer_t;
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struct vlc_timer_t
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@ -176,6 +188,11 @@ VLC_EXPORT( void, vlc_cond_signal, (vlc_cond_t *) );
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VLC_EXPORT( void, vlc_cond_broadcast, (vlc_cond_t *) );
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VLC_EXPORT( void, vlc_cond_wait, (vlc_cond_t *, vlc_mutex_t *) );
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VLC_EXPORT( int, vlc_cond_timedwait, (vlc_cond_t *, vlc_mutex_t *, mtime_t) );
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VLC_EXPORT( void, vlc_rwlock_init, (vlc_rwlock_t *) );
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VLC_EXPORT( void, vlc_rwlock_destroy, (vlc_rwlock_t *) );
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VLC_EXPORT( void, vlc_rwlock_rdlock, (vlc_rwlock_t *) );
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VLC_EXPORT( void, vlc_rwlock_wrlock, (vlc_rwlock_t *) );
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VLC_EXPORT( void, vlc_rwlock_unlock, (vlc_rwlock_t *) );
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VLC_EXPORT( int, vlc_threadvar_create, (vlc_threadvar_t * , void (*) (void *) ) );
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VLC_EXPORT( void, vlc_threadvar_delete, (vlc_threadvar_t *) );
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VLC_EXPORT( int, vlc_threadvar_set, (vlc_threadvar_t, void *) );
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@ -519,6 +519,11 @@ vlc_poll
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vlc_rand_bytes
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vlc_release
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vlc_restorecancel
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vlc_rwlock_destroy
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vlc_rwlock_init
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vlc_rwlock_rdlock
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vlc_rwlock_unlock
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vlc_rwlock_wrlock
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vlc_savecancel
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vlc_sd_Create
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vlc_sd_GetNames
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@ -375,6 +375,51 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
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return val;
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}
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/**
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* Initializes a read/write lock.
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*/
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void vlc_rwlock_init (vlc_rwlock_t *lock)
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{
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if (pthread_rwlock_init (lock, NULL))
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abort ();
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}
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/**
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* Destroys an initialized unused read/write lock.
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*/
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void vlc_rwlock_destroy (vlc_rwlock_t *lock)
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{
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int val = pthread_rwlock_destroy (lock);
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VLC_THREAD_ASSERT ("destroying R/W lock");
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}
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/**
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* Acquires a read/write lock for reading. Recursion is allowed.
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*/
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void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
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{
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int val = pthread_rwlock_rdlock (lock);
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VLC_THREAD_ASSERT ("acquiring R/W lock for reading");
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}
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/**
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* Acquires a read/write lock for writing. Recursion is not allowed.
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*/
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void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
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{
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int val = pthread_rwlock_wrlock (lock);
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VLC_THREAD_ASSERT ("acquiring R/W lock for writing");
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}
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/**
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* Releases a read/write lock.
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*/
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void vlc_rwlock_unlock (vlc_rwlock_t *lock)
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{
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int val = pthread_rwlock_unlock (lock);
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VLC_THREAD_ASSERT ("releasing R/W lock");
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}
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/**
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* Allocates a thread-specific variable.
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* @param key where to store the thread-specific variable handle
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@ -34,6 +34,7 @@
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#include "libvlc.h"
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#include <stdarg.h>
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#include <assert.h>
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#include <limits.h>
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static vlc_threadvar_t cancel_key;
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@ -291,6 +292,82 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
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return (result == WAIT_OBJECT_0) ? 0 : ETIMEDOUT;
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}
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/*** Read/write locks */
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/* SRW (Slim Read Write) locks are available in Vista+ only */
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void vlc_rwlock_init (vlc_rwlock_t *lock)
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{
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vlc_mutex_init (&lock->mutex);
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vlc_cond_init (&lock->read_wait);
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vlc_cond_init (&lock->write_wait);
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lock->readers = 0; /* active readers */
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lock->writers = 0; /* waiting or active writers */
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lock->writer = 0; /* ID of active writer */
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}
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/**
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* Destroys an initialized unused read/write lock.
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*/
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void vlc_rwlock_destroy (vlc_rwlock_t *lock)
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{
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vlc_cond_destroy (&lock->read_wait);
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vlc_cond_destroy (&lock->write_wait);
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vlc_mutex_destroy (&lock->mutex);
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}
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/**
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* Acquires a read/write lock for reading. Recursion is allowed.
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*/
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void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
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{
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vlc_mutex_lock (&lock->mutex);
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while (lock->writers > 0) /* Favor writers to avoid starving */
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vlc_cond_wait (&lock->read_wait, &lock->mutex);
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if (lock->readers == ULONG_MAX)
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abort ();
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lock->readers++;
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vlc_mutex_unlock (&lock->mutex);
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}
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/**
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* Acquires a read/write lock for writing. Recursion is not allowed.
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*/
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void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
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{
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vlc_mutex_lock (&lock->mutex);
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if (lock->writers == ULONG_MAX)
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abort ();
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lock->writers++;
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while ((lock->readers > 0) || (lock->writer != 0))
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vlc_cond_wait (&lock->write_wait, &lock->mutex);
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lock->writer = GetCurrentThreadId ();
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vlc_mutex_unlock (&lock->mutex);
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}
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/**
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* Releases a read/write lock.
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*/
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void vlc_rwlock_unlock (vlc_rwlock_t *lock)
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{
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vlc_mutex_lock (&lock->mutex);
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if (lock->readers > 0)
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lock->readers--; /* Read unlock */
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else
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{
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lock->writer = 0; /* Write unlock */
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assert (lock->writers > 0);
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lock->writers--;
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}
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if (lock->writers > 0)
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{
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if (lock->readers == 0)
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vlc_cond_signal (&lock->write_wait);
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}
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else
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vlc_cond_broadcast (&lock->read_wait);
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vlc_mutex_unlock (&lock->mutex);
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}
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/*** Thread-specific variables (TLS) ***/
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int vlc_threadvar_create (vlc_threadvar_t *p_tls, void (*destr) (void *))
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{
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