[vlc-devel] commit: Read/write locks ( Rémi Denis-Courmont )
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git at videolan.org
Sun Jul 5 19:34:25 CEST 2009
vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Sun Jul 5 20:21:43 2009 +0300| [651698d171a71e20546045a7faa56e606d0ca9a3] | committer: Rémi Denis-Courmont
Read/write locks
> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=651698d171a71e20546045a7faa56e606d0ca9a3
---
include/vlc_threads.h | 17 +++++++++++
src/libvlccore.sym | 5 +++
src/misc/pthread.c | 45 ++++++++++++++++++++++++++++
src/misc/w32thread.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 144 insertions(+), 0 deletions(-)
diff --git a/include/vlc_threads.h b/include/vlc_threads.h
index 4142628..3b6c838 100644
--- a/include/vlc_threads.h
+++ b/include/vlc_threads.h
@@ -107,6 +107,7 @@ typedef pthread_t vlc_thread_t;
typedef pthread_mutex_t vlc_mutex_t;
#define VLC_STATIC_MUTEX PTHREAD_MUTEX_INITIALIZER
typedef pthread_cond_t vlc_cond_t;
+typedef pthread_rwlock_t vlc_rwlock_t;
typedef pthread_key_t vlc_threadvar_t;
typedef struct vlc_timer_t vlc_timer_t;
@@ -143,6 +144,17 @@ typedef struct
#define VLC_STATIC_MUTEX { 0, }
typedef HANDLE vlc_cond_t;
+
+typedef struct
+{
+ vlc_mutex_t mutex;
+ vlc_cond_t read_wait;
+ vlc_cond_t write_wait;
+ unsigned long readers;
+ unsigned long writers;
+ DWORD writer;
+} vlc_rwlock_t;
+
typedef DWORD vlc_threadvar_t;
typedef struct vlc_timer_t vlc_timer_t;
struct vlc_timer_t
@@ -176,6 +188,11 @@ VLC_EXPORT( void, vlc_cond_signal, (vlc_cond_t *) );
VLC_EXPORT( void, vlc_cond_broadcast, (vlc_cond_t *) );
VLC_EXPORT( void, vlc_cond_wait, (vlc_cond_t *, vlc_mutex_t *) );
VLC_EXPORT( int, vlc_cond_timedwait, (vlc_cond_t *, vlc_mutex_t *, mtime_t) );
+VLC_EXPORT( void, vlc_rwlock_init, (vlc_rwlock_t *) );
+VLC_EXPORT( void, vlc_rwlock_destroy, (vlc_rwlock_t *) );
+VLC_EXPORT( void, vlc_rwlock_rdlock, (vlc_rwlock_t *) );
+VLC_EXPORT( void, vlc_rwlock_wrlock, (vlc_rwlock_t *) );
+VLC_EXPORT( void, vlc_rwlock_unlock, (vlc_rwlock_t *) );
VLC_EXPORT( int, vlc_threadvar_create, (vlc_threadvar_t * , void (*) (void *) ) );
VLC_EXPORT( void, vlc_threadvar_delete, (vlc_threadvar_t *) );
VLC_EXPORT( int, vlc_threadvar_set, (vlc_threadvar_t, void *) );
diff --git a/src/libvlccore.sym b/src/libvlccore.sym
index aeaa2e9..3d1a407 100644
--- a/src/libvlccore.sym
+++ b/src/libvlccore.sym
@@ -519,6 +519,11 @@ vlc_poll
vlc_rand_bytes
vlc_release
vlc_restorecancel
+vlc_rwlock_destroy
+vlc_rwlock_init
+vlc_rwlock_rdlock
+vlc_rwlock_unlock
+vlc_rwlock_wrlock
vlc_savecancel
vlc_sd_Create
vlc_sd_GetNames
diff --git a/src/misc/pthread.c b/src/misc/pthread.c
index 9264598..14a48ad 100644
--- a/src/misc/pthread.c
+++ b/src/misc/pthread.c
@@ -376,6 +376,51 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
}
/**
+ * Initializes a read/write lock.
+ */
+void vlc_rwlock_init (vlc_rwlock_t *lock)
+{
+ if (pthread_rwlock_init (lock, NULL))
+ abort ();
+}
+
+/**
+ * Destroys an initialized unused read/write lock.
+ */
+void vlc_rwlock_destroy (vlc_rwlock_t *lock)
+{
+ int val = pthread_rwlock_destroy (lock);
+ VLC_THREAD_ASSERT ("destroying R/W lock");
+}
+
+/**
+ * Acquires a read/write lock for reading. Recursion is allowed.
+ */
+void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
+{
+ int val = pthread_rwlock_rdlock (lock);
+ VLC_THREAD_ASSERT ("acquiring R/W lock for reading");
+}
+
+/**
+ * Acquires a read/write lock for writing. Recursion is not allowed.
+ */
+void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
+{
+ int val = pthread_rwlock_wrlock (lock);
+ VLC_THREAD_ASSERT ("acquiring R/W lock for writing");
+}
+
+/**
+ * Releases a read/write lock.
+ */
+void vlc_rwlock_unlock (vlc_rwlock_t *lock)
+{
+ int val = pthread_rwlock_unlock (lock);
+ VLC_THREAD_ASSERT ("releasing R/W lock");
+}
+
+/**
* Allocates a thread-specific variable.
* @param key where to store the thread-specific variable handle
* @param destr a destruction callback. It is called whenever a thread exits
diff --git a/src/misc/w32thread.c b/src/misc/w32thread.c
index 24f991e..7c722c7 100644
--- a/src/misc/w32thread.c
+++ b/src/misc/w32thread.c
@@ -34,6 +34,7 @@
#include "libvlc.h"
#include <stdarg.h>
#include <assert.h>
+#include <limits.h>
static vlc_threadvar_t cancel_key;
@@ -291,6 +292,82 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
return (result == WAIT_OBJECT_0) ? 0 : ETIMEDOUT;
}
+/*** Read/write locks */
+/* SRW (Slim Read Write) locks are available in Vista+ only */
+void vlc_rwlock_init (vlc_rwlock_t *lock)
+{
+ vlc_mutex_init (&lock->mutex);
+ vlc_cond_init (&lock->read_wait);
+ vlc_cond_init (&lock->write_wait);
+ lock->readers = 0; /* active readers */
+ lock->writers = 0; /* waiting or active writers */
+ lock->writer = 0; /* ID of active writer */
+}
+
+/**
+ * Destroys an initialized unused read/write lock.
+ */
+void vlc_rwlock_destroy (vlc_rwlock_t *lock)
+{
+ vlc_cond_destroy (&lock->read_wait);
+ vlc_cond_destroy (&lock->write_wait);
+ vlc_mutex_destroy (&lock->mutex);
+}
+
+/**
+ * Acquires a read/write lock for reading. Recursion is allowed.
+ */
+void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
+{
+ vlc_mutex_lock (&lock->mutex);
+ while (lock->writers > 0) /* Favor writers to avoid starving */
+ vlc_cond_wait (&lock->read_wait, &lock->mutex);
+ if (lock->readers == ULONG_MAX)
+ abort ();
+ lock->readers++;
+ vlc_mutex_unlock (&lock->mutex);
+}
+
+/**
+ * Acquires a read/write lock for writing. Recursion is not allowed.
+ */
+void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
+{
+ vlc_mutex_lock (&lock->mutex);
+ if (lock->writers == ULONG_MAX)
+ abort ();
+ lock->writers++;
+ while ((lock->readers > 0) || (lock->writer != 0))
+ vlc_cond_wait (&lock->write_wait, &lock->mutex);
+ lock->writer = GetCurrentThreadId ();
+ vlc_mutex_unlock (&lock->mutex);
+}
+
+/**
+ * Releases a read/write lock.
+ */
+void vlc_rwlock_unlock (vlc_rwlock_t *lock)
+{
+ vlc_mutex_lock (&lock->mutex);
+ if (lock->readers > 0)
+ lock->readers--; /* Read unlock */
+ else
+ {
+ lock->writer = 0; /* Write unlock */
+ assert (lock->writers > 0);
+ lock->writers--;
+ }
+
+ if (lock->writers > 0)
+ {
+ if (lock->readers == 0)
+ vlc_cond_signal (&lock->write_wait);
+ }
+ else
+ vlc_cond_broadcast (&lock->read_wait);
+ vlc_mutex_unlock (&lock->mutex);
+}
+
/*** Thread-specific variables (TLS) ***/
int vlc_threadvar_create (vlc_threadvar_t *p_tls, void (*destr) (void *))
{
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