X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=glib%2Fgthread-posix.c;h=f4703f5e1a695d348172c847b6f9d2f9665542a2;hb=49a5d0f6f2aed99cd78f25655f137f4448e47d92;hp=237b8cb3552b45df8c30ef8959c75a5add1161fb;hpb=90679997ec7439ae520c97eb37b5ae36e0da6bba;p=platform%2Fupstream%2Fglib.git
diff --git a/glib/gthread-posix.c b/glib/gthread-posix.c
index 237b8cb..f4703f5 100644
--- a/glib/gthread-posix.c
+++ b/glib/gthread-posix.c
@@ -15,9 +15,7 @@
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 02111-1307, USA.
+ * License along with this library; if not, see .
*/
/*
@@ -42,66 +40,223 @@
#include "config.h"
#include "gthread.h"
+
#include "gthreadprivate.h"
+#include "gslice.h"
+#include "gmessages.h"
+#include "gstrfuncs.h"
+#include "gmain.h"
-#include
#include
+#include
#include
#include
-#include
+#include
+
+#include
+#include
+
+#ifdef HAVE_SCHED_H
+#include
+#endif
+#ifdef HAVE_SYS_PRCTL_H
+#include
+#endif
+#ifdef G_OS_WIN32
+#include
+#endif
+
+/* clang defines __ATOMIC_SEQ_CST but doesn't support the GCC extension */
+#if defined(HAVE_FUTEX) && defined(__ATOMIC_SEQ_CST) && !defined(__clang__)
+#define USE_NATIVE_MUTEX
+#endif
static void
g_thread_abort (gint status,
const gchar *function)
{
fprintf (stderr, "GLib (gthread-posix.c): Unexpected error from C library during '%s': %s. Aborting.\n",
- strerror (status), function);
+ function, strerror (status));
abort ();
}
/* {{{1 GMutex */
-void
-g_mutex_init (GMutex *mutex)
+
+#if !defined(USE_NATIVE_MUTEX)
+
+static pthread_mutex_t *
+g_mutex_impl_new (void)
{
+ pthread_mutexattr_t *pattr = NULL;
+ pthread_mutex_t *mutex;
gint status;
+#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+ pthread_mutexattr_t attr;
+#endif
+
+ mutex = malloc (sizeof (pthread_mutex_t));
+ if G_UNLIKELY (mutex == NULL)
+ g_thread_abort (errno, "malloc");
- if G_UNLIKELY ((status = pthread_mutex_init (&mutex->impl, NULL)) != 0)
+#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+ pthread_mutexattr_init (&attr);
+ pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
+ pattr = &attr;
+#endif
+
+ if G_UNLIKELY ((status = pthread_mutex_init (mutex, pattr)) != 0)
g_thread_abort (status, "pthread_mutex_init");
+
+#ifdef PTHREAD_ADAPTIVE_MUTEX_NP
+ pthread_mutexattr_destroy (&attr);
+#endif
+
+ return mutex;
+}
+
+static void
+g_mutex_impl_free (pthread_mutex_t *mutex)
+{
+ pthread_mutex_destroy (mutex);
+ free (mutex);
}
+static inline pthread_mutex_t *
+g_mutex_get_impl (GMutex *mutex)
+{
+ pthread_mutex_t *impl = g_atomic_pointer_get (&mutex->p);
+
+ if G_UNLIKELY (impl == NULL)
+ {
+ impl = g_mutex_impl_new ();
+ if (!g_atomic_pointer_compare_and_exchange (&mutex->p, NULL, impl))
+ g_mutex_impl_free (impl);
+ impl = mutex->p;
+ }
+
+ return impl;
+}
+
+
+/**
+ * g_mutex_init:
+ * @mutex: an uninitialized #GMutex
+ *
+ * Initializes a #GMutex so that it can be used.
+ *
+ * This function is useful to initialize a mutex that has been
+ * allocated on the stack, or as part of a larger structure.
+ * It is not necessary to initialize a mutex that has been
+ * statically allocated.
+ *
+ * |[
+ * typedef struct {
+ * GMutex m;
+ * ...
+ * } Blob;
+ *
+ * Blob *b;
+ *
+ * b = g_new (Blob, 1);
+ * g_mutex_init (&b->m);
+ * ]|
+ *
+ * To undo the effect of g_mutex_init() when a mutex is no longer
+ * needed, use g_mutex_clear().
+ *
+ * Calling g_mutex_init() on an already initialized #GMutex leads
+ * to undefined behaviour.
+ *
+ * Since: 2.32
+ */
void
-g_mutex_clear (GMutex *mutex)
+g_mutex_init (GMutex *mutex)
{
- gint status;
+ mutex->p = g_mutex_impl_new ();
+}
- if G_UNLIKELY ((status = pthread_mutex_destroy (&mutex->impl)) != 0)
- g_thread_abort (status, "pthread_mutex_destroy");
+/**
+ * g_mutex_clear:
+ * @mutex: an initialized #GMutex
+ *
+ * Frees the resources allocated to a mutex with g_mutex_init().
+ *
+ * This function should not be used with a #GMutex that has been
+ * statically allocated.
+ *
+ * Calling g_mutex_clear() on a locked mutex leads to undefined
+ * behaviour.
+ *
+ * Sine: 2.32
+ */
+void
+g_mutex_clear (GMutex *mutex)
+{
+ g_mutex_impl_free (mutex->p);
}
+/**
+ * g_mutex_lock:
+ * @mutex: a #GMutex
+ *
+ * Locks @mutex. If @mutex is already locked by another thread, the
+ * current thread will block until @mutex is unlocked by the other
+ * thread.
+ *
+ * #GMutex is neither guaranteed to be recursive nor to be
+ * non-recursive. As such, calling g_mutex_lock() on a #GMutex that has
+ * already been locked by the same thread results in undefined behaviour
+ * (including but not limited to deadlocks).
+ */
void
g_mutex_lock (GMutex *mutex)
{
gint status;
- if G_UNLIKELY ((status = pthread_mutex_lock (&mutex->impl)) != 0)
+ if G_UNLIKELY ((status = pthread_mutex_lock (g_mutex_get_impl (mutex))) != 0)
g_thread_abort (status, "pthread_mutex_lock");
}
+/**
+ * g_mutex_unlock:
+ * @mutex: a #GMutex
+ *
+ * Unlocks @mutex. If another thread is blocked in a g_mutex_lock()
+ * call for @mutex, it will become unblocked and can lock @mutex itself.
+ *
+ * Calling g_mutex_unlock() on a mutex that is not locked by the
+ * current thread leads to undefined behaviour.
+ */
void
g_mutex_unlock (GMutex *mutex)
{
gint status;
- if G_UNLIKELY ((status = pthread_mutex_unlock (&mutex->impl)) != 0)
- g_thread_abort (status, "pthread_mutex_lock");
+ if G_UNLIKELY ((status = pthread_mutex_unlock (g_mutex_get_impl (mutex))) != 0)
+ g_thread_abort (status, "pthread_mutex_unlock");
}
+/**
+ * g_mutex_trylock:
+ * @mutex: a #GMutex
+ *
+ * Tries to lock @mutex. If @mutex is already locked by another thread,
+ * it immediately returns %FALSE. Otherwise it locks @mutex and returns
+ * %TRUE.
+ *
+ * #GMutex is neither guaranteed to be recursive nor to be
+ * non-recursive. As such, calling g_mutex_lock() on a #GMutex that has
+ * already been locked by the same thread results in undefined behaviour
+ * (including but not limited to deadlocks or arbitrary return values).
+
+ * Returns: %TRUE if @mutex could be locked
+ */
gboolean
g_mutex_trylock (GMutex *mutex)
{
gint status;
- if G_LIKELY ((status = pthread_mutex_trylock (&mutex->impl)) == 0)
+ if G_LIKELY ((status = pthread_mutex_trylock (g_mutex_get_impl (mutex))) == 0)
return TRUE;
if G_UNLIKELY (status != EBUSY)
@@ -110,93 +265,647 @@ g_mutex_trylock (GMutex *mutex)
return FALSE;
}
-/* {{{1 GCond */
+#endif /* !defined(USE_NATIVE_MUTEX) */
+
+/* {{{1 GRecMutex */
+
+static pthread_mutex_t *
+g_rec_mutex_impl_new (void)
+{
+ pthread_mutexattr_t attr;
+ pthread_mutex_t *mutex;
+ mutex = malloc (sizeof (pthread_mutex_t));
+ if G_UNLIKELY (mutex == NULL)
+ g_thread_abort (errno, "malloc");
+
+ pthread_mutexattr_init (&attr);
+ pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
+ pthread_mutex_init (mutex, &attr);
+ pthread_mutexattr_destroy (&attr);
+
+ return mutex;
+}
+
+static void
+g_rec_mutex_impl_free (pthread_mutex_t *mutex)
+{
+ pthread_mutex_destroy (mutex);
+ free (mutex);
+}
+
+static inline pthread_mutex_t *
+g_rec_mutex_get_impl (GRecMutex *rec_mutex)
+{
+ pthread_mutex_t *impl = g_atomic_pointer_get (&rec_mutex->p);
+
+ if G_UNLIKELY (impl == NULL)
+ {
+ impl = g_rec_mutex_impl_new ();
+ if (!g_atomic_pointer_compare_and_exchange (&rec_mutex->p, NULL, impl))
+ g_rec_mutex_impl_free (impl);
+ impl = rec_mutex->p;
+ }
+
+ return impl;
+}
+
+/**
+ * g_rec_mutex_init:
+ * @rec_mutex: an uninitialized #GRecMutex
+ *
+ * Initializes a #GRecMutex so that it can be used.
+ *
+ * This function is useful to initialize a recursive mutex
+ * that has been allocated on the stack, or as part of a larger
+ * structure.
+ *
+ * It is not necessary to initialise a recursive mutex that has been
+ * statically allocated.
+ *
+ * |[
+ * typedef struct {
+ * GRecMutex m;
+ * ...
+ * } Blob;
+ *
+ * Blob *b;
+ *
+ * b = g_new (Blob, 1);
+ * g_rec_mutex_init (&b->m);
+ * ]|
+ *
+ * Calling g_rec_mutex_init() on an already initialized #GRecMutex
+ * leads to undefined behaviour.
+ *
+ * To undo the effect of g_rec_mutex_init() when a recursive mutex
+ * is no longer needed, use g_rec_mutex_clear().
+ *
+ * Since: 2.32
+ */
void
-g_cond_init (GCond *cond)
+g_rec_mutex_init (GRecMutex *rec_mutex)
+{
+ rec_mutex->p = g_rec_mutex_impl_new ();
+}
+
+/**
+ * g_rec_mutex_clear:
+ * @rec_mutex: an initialized #GRecMutex
+ *
+ * Frees the resources allocated to a recursive mutex with
+ * g_rec_mutex_init().
+ *
+ * This function should not be used with a #GRecMutex that has been
+ * statically allocated.
+ *
+ * Calling g_rec_mutex_clear() on a locked recursive mutex leads
+ * to undefined behaviour.
+ *
+ * Sine: 2.32
+ */
+void
+g_rec_mutex_clear (GRecMutex *rec_mutex)
+{
+ g_rec_mutex_impl_free (rec_mutex->p);
+}
+
+/**
+ * g_rec_mutex_lock:
+ * @rec_mutex: a #GRecMutex
+ *
+ * Locks @rec_mutex. If @rec_mutex is already locked by another
+ * thread, the current thread will block until @rec_mutex is
+ * unlocked by the other thread. If @rec_mutex is already locked
+ * by the current thread, the 'lock count' of @rec_mutex is increased.
+ * The mutex will only become available again when it is unlocked
+ * as many times as it has been locked.
+ *
+ * Since: 2.32
+ */
+void
+g_rec_mutex_lock (GRecMutex *mutex)
+{
+ pthread_mutex_lock (g_rec_mutex_get_impl (mutex));
+}
+
+/**
+ * g_rec_mutex_unlock:
+ * @rec_mutex: a #GRecMutex
+ *
+ * Unlocks @rec_mutex. If another thread is blocked in a
+ * g_rec_mutex_lock() call for @rec_mutex, it will become unblocked
+ * and can lock @rec_mutex itself.
+ *
+ * Calling g_rec_mutex_unlock() on a recursive mutex that is not
+ * locked by the current thread leads to undefined behaviour.
+ *
+ * Since: 2.32
+ */
+void
+g_rec_mutex_unlock (GRecMutex *rec_mutex)
{
+ pthread_mutex_unlock (rec_mutex->p);
+}
+
+/**
+ * g_rec_mutex_trylock:
+ * @rec_mutex: a #GRecMutex
+ *
+ * Tries to lock @rec_mutex. If @rec_mutex is already locked
+ * by another thread, it immediately returns %FALSE. Otherwise
+ * it locks @rec_mutex and returns %TRUE.
+ *
+ * Returns: %TRUE if @rec_mutex could be locked
+ *
+ * Since: 2.32
+ */
+gboolean
+g_rec_mutex_trylock (GRecMutex *rec_mutex)
+{
+ if (pthread_mutex_trylock (g_rec_mutex_get_impl (rec_mutex)) != 0)
+ return FALSE;
+
+ return TRUE;
+}
+
+/* {{{1 GRWLock */
+
+static pthread_rwlock_t *
+g_rw_lock_impl_new (void)
+{
+ pthread_rwlock_t *rwlock;
gint status;
- if G_UNLIKELY ((status = pthread_cond_init (&cond->impl, NULL)) != 0)
+ rwlock = malloc (sizeof (pthread_rwlock_t));
+ if G_UNLIKELY (rwlock == NULL)
+ g_thread_abort (errno, "malloc");
+
+ if G_UNLIKELY ((status = pthread_rwlock_init (rwlock, NULL)) != 0)
+ g_thread_abort (status, "pthread_rwlock_init");
+
+ return rwlock;
+}
+
+static void
+g_rw_lock_impl_free (pthread_rwlock_t *rwlock)
+{
+ pthread_rwlock_destroy (rwlock);
+ free (rwlock);
+}
+
+static inline pthread_rwlock_t *
+g_rw_lock_get_impl (GRWLock *lock)
+{
+ pthread_rwlock_t *impl = g_atomic_pointer_get (&lock->p);
+
+ if G_UNLIKELY (impl == NULL)
+ {
+ impl = g_rw_lock_impl_new ();
+ if (!g_atomic_pointer_compare_and_exchange (&lock->p, NULL, impl))
+ g_rw_lock_impl_free (impl);
+ impl = lock->p;
+ }
+
+ return impl;
+}
+
+/**
+ * g_rw_lock_init:
+ * @rw_lock: an uninitialized #GRWLock
+ *
+ * Initializes a #GRWLock so that it can be used.
+ *
+ * This function is useful to initialize a lock that has been
+ * allocated on the stack, or as part of a larger structure. It is not
+ * necessary to initialise a reader-writer lock that has been statically
+ * allocated.
+ *
+ * |[
+ * typedef struct {
+ * GRWLock l;
+ * ...
+ * } Blob;
+ *
+ * Blob *b;
+ *
+ * b = g_new (Blob, 1);
+ * g_rw_lock_init (&b->l);
+ * ]|
+ *
+ * To undo the effect of g_rw_lock_init() when a lock is no longer
+ * needed, use g_rw_lock_clear().
+ *
+ * Calling g_rw_lock_init() on an already initialized #GRWLock leads
+ * to undefined behaviour.
+ *
+ * Since: 2.32
+ */
+void
+g_rw_lock_init (GRWLock *rw_lock)
+{
+ rw_lock->p = g_rw_lock_impl_new ();
+}
+
+/**
+ * g_rw_lock_clear:
+ * @rw_lock: an initialized #GRWLock
+ *
+ * Frees the resources allocated to a lock with g_rw_lock_init().
+ *
+ * This function should not be used with a #GRWLock that has been
+ * statically allocated.
+ *
+ * Calling g_rw_lock_clear() when any thread holds the lock
+ * leads to undefined behaviour.
+ *
+ * Sine: 2.32
+ */
+void
+g_rw_lock_clear (GRWLock *rw_lock)
+{
+ g_rw_lock_impl_free (rw_lock->p);
+}
+
+/**
+ * g_rw_lock_writer_lock:
+ * @rw_lock: a #GRWLock
+ *
+ * Obtain a write lock on @rw_lock. If any thread already holds
+ * a read or write lock on @rw_lock, the current thread will block
+ * until all other threads have dropped their locks on @rw_lock.
+ *
+ * Since: 2.32
+ */
+void
+g_rw_lock_writer_lock (GRWLock *rw_lock)
+{
+ pthread_rwlock_wrlock (g_rw_lock_get_impl (rw_lock));
+}
+
+/**
+ * g_rw_lock_writer_trylock:
+ * @rw_lock: a #GRWLock
+ *
+ * Tries to obtain a write lock on @rw_lock. If any other thread holds
+ * a read or write lock on @rw_lock, it immediately returns %FALSE.
+ * Otherwise it locks @rw_lock and returns %TRUE.
+ *
+ * Returns: %TRUE if @rw_lock could be locked
+ *
+ * Since: 2.32
+ */
+gboolean
+g_rw_lock_writer_trylock (GRWLock *rw_lock)
+{
+ if (pthread_rwlock_trywrlock (g_rw_lock_get_impl (rw_lock)) != 0)
+ return FALSE;
+
+ return TRUE;
+}
+
+/**
+ * g_rw_lock_writer_unlock:
+ * @rw_lock: a #GRWLock
+ *
+ * Release a write lock on @rw_lock.
+ *
+ * Calling g_rw_lock_writer_unlock() on a lock that is not held
+ * by the current thread leads to undefined behaviour.
+ *
+ * Since: 2.32
+ */
+void
+g_rw_lock_writer_unlock (GRWLock *rw_lock)
+{
+ pthread_rwlock_unlock (g_rw_lock_get_impl (rw_lock));
+}
+
+/**
+ * g_rw_lock_reader_lock:
+ * @rw_lock: a #GRWLock
+ *
+ * Obtain a read lock on @rw_lock. If another thread currently holds
+ * the write lock on @rw_lock or blocks waiting for it, the current
+ * thread will block. Read locks can be taken recursively.
+ *
+ * It is implementation-defined how many threads are allowed to
+ * hold read locks on the same lock simultaneously.
+ *
+ * Since: 2.32
+ */
+void
+g_rw_lock_reader_lock (GRWLock *rw_lock)
+{
+ pthread_rwlock_rdlock (g_rw_lock_get_impl (rw_lock));
+}
+
+/**
+ * g_rw_lock_reader_trylock:
+ * @rw_lock: a #GRWLock
+ *
+ * Tries to obtain a read lock on @rw_lock and returns %TRUE if
+ * the read lock was successfully obtained. Otherwise it
+ * returns %FALSE.
+ *
+ * Returns: %TRUE if @rw_lock could be locked
+ *
+ * Since: 2.32
+ */
+gboolean
+g_rw_lock_reader_trylock (GRWLock *rw_lock)
+{
+ if (pthread_rwlock_tryrdlock (g_rw_lock_get_impl (rw_lock)) != 0)
+ return FALSE;
+
+ return TRUE;
+}
+
+/**
+ * g_rw_lock_reader_unlock:
+ * @rw_lock: a #GRWLock
+ *
+ * Release a read lock on @rw_lock.
+ *
+ * Calling g_rw_lock_reader_unlock() on a lock that is not held
+ * by the current thread leads to undefined behaviour.
+ *
+ * Since: 2.32
+ */
+void
+g_rw_lock_reader_unlock (GRWLock *rw_lock)
+{
+ pthread_rwlock_unlock (g_rw_lock_get_impl (rw_lock));
+}
+
+/* {{{1 GCond */
+
+#if !defined(USE_NATIVE_MUTEX)
+
+static pthread_cond_t *
+g_cond_impl_new (void)
+{
+ pthread_condattr_t attr;
+ pthread_cond_t *cond;
+ gint status;
+
+ pthread_condattr_init (&attr);
+
+#ifdef HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
+#elif defined (HAVE_PTHREAD_CONDATTR_SETCLOCK) && defined (CLOCK_MONOTONIC)
+ if G_UNLIKELY ((status = pthread_condattr_setclock (&attr, CLOCK_MONOTONIC)) != 0)
+ g_thread_abort (status, "pthread_condattr_setclock");
+#else
+#error Cannot support GCond on your platform.
+#endif
+
+ cond = malloc (sizeof (pthread_cond_t));
+ if G_UNLIKELY (cond == NULL)
+ g_thread_abort (errno, "malloc");
+
+ if G_UNLIKELY ((status = pthread_cond_init (cond, &attr)) != 0)
g_thread_abort (status, "pthread_cond_init");
+
+ pthread_condattr_destroy (&attr);
+
+ return cond;
+}
+
+static void
+g_cond_impl_free (pthread_cond_t *cond)
+{
+ pthread_cond_destroy (cond);
+ free (cond);
+}
+
+static inline pthread_cond_t *
+g_cond_get_impl (GCond *cond)
+{
+ pthread_cond_t *impl = g_atomic_pointer_get (&cond->p);
+
+ if G_UNLIKELY (impl == NULL)
+ {
+ impl = g_cond_impl_new ();
+ if (!g_atomic_pointer_compare_and_exchange (&cond->p, NULL, impl))
+ g_cond_impl_free (impl);
+ impl = cond->p;
+ }
+
+ return impl;
+}
+
+/**
+ * g_cond_init:
+ * @cond: an uninitialized #GCond
+ *
+ * Initialises a #GCond so that it can be used.
+ *
+ * This function is useful to initialise a #GCond that has been
+ * allocated as part of a larger structure. It is not necessary to
+ * initialise a #GCond that has been statically allocated.
+ *
+ * To undo the effect of g_cond_init() when a #GCond is no longer
+ * needed, use g_cond_clear().
+ *
+ * Calling g_cond_init() on an already-initialised #GCond leads
+ * to undefined behaviour.
+ *
+ * Since: 2.32
+ */
+void
+g_cond_init (GCond *cond)
+{
+ cond->p = g_cond_impl_new ();
}
+/**
+ * g_cond_clear:
+ * @cond: an initialised #GCond
+ *
+ * Frees the resources allocated to a #GCond with g_cond_init().
+ *
+ * This function should not be used with a #GCond that has been
+ * statically allocated.
+ *
+ * Calling g_cond_clear() for a #GCond on which threads are
+ * blocking leads to undefined behaviour.
+ *
+ * Since: 2.32
+ */
void
g_cond_clear (GCond *cond)
{
- gint status;
-
- if G_UNLIKELY ((status = pthread_cond_destroy (&cond->impl)) != 0)
- g_thread_abort (status, "pthread_cond_destroy");
+ g_cond_impl_free (cond->p);
}
+/**
+ * g_cond_wait:
+ * @cond: a #GCond
+ * @mutex: a #GMutex that is currently locked
+ *
+ * Atomically releases @mutex and waits until @cond is signalled.
+ * When this function returns, @mutex is locked again and owned by the
+ * calling thread.
+ *
+ * When using condition variables, it is possible that a spurious wakeup
+ * may occur (ie: g_cond_wait() returns even though g_cond_signal() was
+ * not called). It's also possible that a stolen wakeup may occur.
+ * This is when g_cond_signal() is called, but another thread acquires
+ * @mutex before this thread and modifies the state of the program in
+ * such a way that when g_cond_wait() is able to return, the expected
+ * condition is no longer met.
+ *
+ * For this reason, g_cond_wait() must always be used in a loop. See
+ * the documentation for #GCond for a complete example.
+ **/
void
g_cond_wait (GCond *cond,
GMutex *mutex)
{
gint status;
- if G_UNLIKELY ((status = pthread_cond_wait (&cond->impl, &mutex->impl)) != 0)
+ if G_UNLIKELY ((status = pthread_cond_wait (g_cond_get_impl (cond), g_mutex_get_impl (mutex))) != 0)
g_thread_abort (status, "pthread_cond_wait");
}
+/**
+ * g_cond_signal:
+ * @cond: a #GCond
+ *
+ * If threads are waiting for @cond, at least one of them is unblocked.
+ * If no threads are waiting for @cond, this function has no effect.
+ * It is good practice to hold the same lock as the waiting thread
+ * while calling this function, though not required.
+ */
void
g_cond_signal (GCond *cond)
{
gint status;
- if G_UNLIKELY ((status = pthread_cond_signal (&cond->impl)) != 0)
+ if G_UNLIKELY ((status = pthread_cond_signal (g_cond_get_impl (cond))) != 0)
g_thread_abort (status, "pthread_cond_signal");
}
+/**
+ * g_cond_broadcast:
+ * @cond: a #GCond
+ *
+ * If threads are waiting for @cond, all of them are unblocked.
+ * If no threads are waiting for @cond, this function has no effect.
+ * It is good practice to lock the same mutex as the waiting threads
+ * while calling this function, though not required.
+ */
void
g_cond_broadcast (GCond *cond)
{
gint status;
- if G_UNLIKELY ((status = pthread_cond_broadcast (&cond->impl)) != 0)
+ if G_UNLIKELY ((status = pthread_cond_broadcast (g_cond_get_impl (cond))) != 0)
g_thread_abort (status, "pthread_cond_broadcast");
}
+/**
+ * g_cond_wait_until:
+ * @cond: a #GCond
+ * @mutex: a #GMutex that is currently locked
+ * @end_time: the monotonic time to wait until
+ *
+ * Waits until either @cond is signalled or @end_time has passed.
+ *
+ * As with g_cond_wait() it is possible that a spurious or stolen wakeup
+ * could occur. For that reason, waiting on a condition variable should
+ * always be in a loop, based on an explicitly-checked predicate.
+ *
+ * %TRUE is returned if the condition variable was signalled (or in the
+ * case of a spurious wakeup). %FALSE is returned if @end_time has
+ * passed.
+ *
+ * The following code shows how to correctly perform a timed wait on a
+ * condition variable (extending the example presented in the
+ * documentation for #GCond):
+ *
+ * |[
+ * gpointer
+ * pop_data_timed (void)
+ * {
+ * gint64 end_time;
+ * gpointer data;
+ *
+ * g_mutex_lock (&data_mutex);
+ *
+ * end_time = g_get_monotonic_time () + 5 * G_TIME_SPAN_SECOND;
+ * while (!current_data)
+ * if (!g_cond_wait_until (&data_cond, &data_mutex, end_time))
+ * {
+ * // timeout has passed.
+ * g_mutex_unlock (&data_mutex);
+ * return NULL;
+ * }
+ *
+ * // there is data for us
+ * data = current_data;
+ * current_data = NULL;
+ *
+ * g_mutex_unlock (&data_mutex);
+ *
+ * return data;
+ * }
+ * ]|
+ *
+ * Notice that the end time is calculated once, before entering the
+ * loop and reused. This is the motivation behind the use of absolute
+ * time on this API -- if a relative time of 5 seconds were passed
+ * directly to the call and a spurious wakeup occurred, the program would
+ * have to start over waiting again (which would lead to a total wait
+ * time of more than 5 seconds).
+ *
+ * Returns: %TRUE on a signal, %FALSE on a timeout
+ * Since: 2.32
+ **/
gboolean
-g_cond_timed_wait (GCond *cond,
- GMutex *mutex,
- GTimeVal *abs_time)
+g_cond_wait_until (GCond *cond,
+ GMutex *mutex,
+ gint64 end_time)
{
- struct timespec end_time;
+ struct timespec ts;
gint status;
- if (abs_time == NULL)
- {
- g_cond_wait (cond, mutex);
- return TRUE;
- }
-
- end_time.tv_sec = abs_time->tv_sec;
- end_time.tv_nsec = abs_time->tv_usec * 1000;
-
- if ((status = pthread_cond_timedwait (&cond->impl, &mutex->impl, &end_time)) == 0)
- return TRUE;
+#ifdef HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
+ /* end_time is given relative to the monotonic clock as returned by
+ * g_get_monotonic_time().
+ *
+ * Since this pthreads wants the relative time, convert it back again.
+ */
+ {
+ gint64 now = g_get_monotonic_time ();
+ gint64 relative;
- if G_UNLIKELY (status != ETIMEDOUT)
- g_thread_abort (status, "pthread_cond_timedwait");
+ if (end_time <= now)
+ return FALSE;
- return FALSE;
-}
+ relative = end_time - now;
-gboolean
-g_cond_timedwait (GCond *cond,
- GMutex *mutex,
- gint64 abs_time)
-{
- struct timespec end_time;
- gint status;
+ ts.tv_sec = relative / 1000000;
+ ts.tv_nsec = (relative % 1000000) * 1000;
- end_time.tv_sec = abs_time / 1000000;
- end_time.tv_nsec = (abs_time % 1000000) * 1000;
+ if ((status = pthread_cond_timedwait_relative_np (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &ts)) == 0)
+ return TRUE;
+ }
+#elif defined (HAVE_PTHREAD_CONDATTR_SETCLOCK) && defined (CLOCK_MONOTONIC)
+ /* This is the exact check we used during init to set the clock to
+ * monotonic, so if we're in this branch, timedwait() will already be
+ * expecting a monotonic clock.
+ */
+ {
+ ts.tv_sec = end_time / 1000000;
+ ts.tv_nsec = (end_time % 1000000) * 1000;
- if ((status = pthread_cond_timedwait (&cond->impl, &mutex->impl, &end_time)) == 0)
- return TRUE;
+ if ((status = pthread_cond_timedwait (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &ts)) == 0)
+ return TRUE;
+ }
+#else
+#error Cannot support GCond on your platform.
+#endif
if G_UNLIKELY (status != ETIMEDOUT)
g_thread_abort (status, "pthread_cond_timedwait");
@@ -204,73 +913,202 @@ g_cond_timedwait (GCond *cond,
return FALSE;
}
+#endif /* defined(USE_NATIVE_MUTEX) */
+
/* {{{1 GPrivate */
-GPrivate *
-g_private_new (GDestroyNotify notify)
+/**
+ * GPrivate:
+ *
+ * The #GPrivate struct is an opaque data structure to represent a
+ * thread-local data key. It is approximately equivalent to the
+ * pthread_setspecific()/pthread_getspecific() APIs on POSIX and to
+ * TlsSetValue()/TlsGetValue() on Windows.
+ *
+ * If you don't already know why you might want this functionality,
+ * then you probably don't need it.
+ *
+ * #GPrivate is a very limited resource (as far as 128 per program,
+ * shared between all libraries). It is also not possible to destroy a
+ * #GPrivate after it has been used. As such, it is only ever acceptable
+ * to use #GPrivate in static scope, and even then sparingly so.
+ *
+ * See G_PRIVATE_INIT() for a couple of examples.
+ *
+ * The #GPrivate structure should be considered opaque. It should only
+ * be accessed via the g_private_ functions.
+ */
+
+/**
+ * G_PRIVATE_INIT:
+ * @notify: a #GDestroyNotify
+ *
+ * A macro to assist with the static initialisation of a #GPrivate.
+ *
+ * This macro is useful for the case that a #GDestroyNotify function
+ * should be associated the key. This is needed when the key will be
+ * used to point at memory that should be deallocated when the thread
+ * exits.
+ *
+ * Additionally, the #GDestroyNotify will also be called on the previous
+ * value stored in the key when g_private_replace() is used.
+ *
+ * If no #GDestroyNotify is needed, then use of this macro is not
+ * required -- if the #GPrivate is declared in static scope then it will
+ * be properly initialised by default (ie: to all zeros). See the
+ * examples below.
+ *
+ * |[
+ * static GPrivate name_key = G_PRIVATE_INIT (g_free);
+ *
+ * // return value should not be freed
+ * const gchar *
+ * get_local_name (void)
+ * {
+ * return g_private_get (&name_key);
+ * }
+ *
+ * void
+ * set_local_name (const gchar *name)
+ * {
+ * g_private_replace (&name_key, g_strdup (name));
+ * }
+ *
+ *
+ * static GPrivate count_key; // no free function
+ *
+ * gint
+ * get_local_count (void)
+ * {
+ * return GPOINTER_TO_INT (g_private_get (&count_key));
+ * }
+ *
+ * void
+ * set_local_count (gint count)
+ * {
+ * g_private_set (&count_key, GINT_TO_POINTER (count));
+ * }
+ * ]|
+ *
+ * Since: 2.32
+ **/
+
+static pthread_key_t *
+g_private_impl_new (GDestroyNotify notify)
{
- GPrivate *key;
+ pthread_key_t *key;
+ gint status;
- key = malloc (sizeof (GPrivate));
+ key = malloc (sizeof (pthread_key_t));
if G_UNLIKELY (key == NULL)
g_thread_abort (errno, "malloc");
- g_private_init (key, notify);
+ status = pthread_key_create (key, notify);
+ if G_UNLIKELY (status != 0)
+ g_thread_abort (status, "pthread_key_create");
return key;
}
-void
-g_private_init (GPrivate *key,
- GDestroyNotify notify)
+static void
+g_private_impl_free (pthread_key_t *key)
{
- pthread_key_create (&key->key, notify);
- key->ready = TRUE;
+ gint status;
+
+ status = pthread_key_delete (*key);
+ if G_UNLIKELY (status != 0)
+ g_thread_abort (status, "pthread_key_delete");
+ free (key);
+}
+
+static inline pthread_key_t *
+g_private_get_impl (GPrivate *key)
+{
+ pthread_key_t *impl = g_atomic_pointer_get (&key->p);
+
+ if G_UNLIKELY (impl == NULL)
+ {
+ impl = g_private_impl_new (key->notify);
+ if (!g_atomic_pointer_compare_and_exchange (&key->p, NULL, impl))
+ {
+ g_private_impl_free (impl);
+ impl = key->p;
+ }
+ }
+
+ return impl;
}
+/**
+ * g_private_get:
+ * @key: a #GPrivate
+ *
+ * Returns the current value of the thread local variable @key.
+ *
+ * If the value has not yet been set in this thread, %NULL is returned.
+ * Values are never copied between threads (when a new thread is
+ * created, for example).
+ *
+ * Returns: the thread-local value
+ */
gpointer
g_private_get (GPrivate *key)
{
- if (!key->ready)
- return key->single_value;
-
/* quote POSIX: No errors are returned from pthread_getspecific(). */
- return pthread_getspecific (key->key);
+ return pthread_getspecific (*g_private_get_impl (key));
}
+/**
+ * g_private_set:
+ * @key: a #GPrivate
+ * @value: the new value
+ *
+ * Sets the thread local variable @key to have the value @value in the
+ * current thread.
+ *
+ * This function differs from g_private_replace() in the following way:
+ * the #GDestroyNotify for @key is not called on the old value.
+ */
void
g_private_set (GPrivate *key,
gpointer value)
{
gint status;
- if (!key->ready)
- {
- key->single_value = value;
- return;
- }
-
- if G_UNLIKELY ((status = pthread_setspecific (key->key, value)) != 0)
+ if G_UNLIKELY ((status = pthread_setspecific (*g_private_get_impl (key), value)) != 0)
g_thread_abort (status, "pthread_setspecific");
}
-/* {{{1 GThread */
+/**
+ * g_private_replace:
+ * @key: a #GPrivate
+ * @value: the new value
+ *
+ * Sets the thread local variable @key to have the value @value in the
+ * current thread.
+ *
+ * This function differs from g_private_set() in the following way: if
+ * the previous value was non-%NULL then the #GDestroyNotify handler for
+ * @key is run on it.
+ *
+ * Since: 2.32
+ **/
+void
+g_private_replace (GPrivate *key,
+ gpointer value)
+{
+ pthread_key_t *impl = g_private_get_impl (key);
+ gpointer old;
+ gint status;
-#include "glib.h"
-#include "gthreadprivate.h"
+ old = pthread_getspecific (*impl);
+ if (old && key->notify)
+ key->notify (old);
-#include
-#include
-#include
-#ifdef HAVE_SYS_TIME_H
-# include
-#endif
-#ifdef HAVE_UNISTD_H
-# include
-#endif
+ if G_UNLIKELY ((status = pthread_setspecific (*impl, value)) != 0)
+ g_thread_abort (status, "pthread_setspecific");
+}
-#ifdef HAVE_SCHED_H
-#include
-#endif
+/* {{{1 GThread */
#define posix_check_err(err, name) G_STMT_START{ \
int error = (err); \
@@ -282,228 +1120,327 @@ g_private_set (GPrivate *key,
#define posix_check_cmd(cmd) posix_check_err (cmd, #cmd)
-#ifdef G_ENABLE_DEBUG
-static gboolean posix_check_cmd_prio_warned = FALSE;
-# define posix_check_cmd_prio(cmd) G_STMT_START{ \
- int err = (cmd); \
- if (err == EPERM) \
- { \
- if (!posix_check_cmd_prio_warned) \
- { \
- posix_check_cmd_prio_warned = TRUE; \
- g_warning ("Priorities can only be changed " \
- "(resp. increased) by root."); \
- } \
- } \
- else \
- posix_check_err (err, #cmd); \
- }G_STMT_END
-#else /* G_ENABLE_DEBUG */
-# define posix_check_cmd_prio(cmd) G_STMT_START{ \
- int err = (cmd); \
- if (err != EPERM) \
- posix_check_err (err, #cmd); \
- }G_STMT_END
-#endif /* G_ENABLE_DEBUG */
-
-#if defined (POSIX_MIN_PRIORITY) && defined (POSIX_MAX_PRIORITY)
-# define HAVE_PRIORITIES 1
-static gint priority_normal_value;
-# ifdef __FreeBSD__
- /* FreeBSD threads use different priority values from the POSIX_
- * defines so we just set them here. The corresponding macros
- * PTHREAD_MIN_PRIORITY and PTHREAD_MAX_PRIORITY are implied to be
- * exported by the docs, but they aren't.
- */
-# define PRIORITY_LOW_VALUE 0
-# define PRIORITY_URGENT_VALUE 31
-# else /* !__FreeBSD__ */
-# define PRIORITY_LOW_VALUE POSIX_MIN_PRIORITY
-# define PRIORITY_URGENT_VALUE POSIX_MAX_PRIORITY
-# endif /* !__FreeBSD__ */
-# define PRIORITY_NORMAL_VALUE priority_normal_value
-
-# define PRIORITY_HIGH_VALUE \
- ((PRIORITY_NORMAL_VALUE + PRIORITY_URGENT_VALUE * 2) / 3)
-
-static gint
-g_thread_priority_map (GThreadPriority priority)
-{
- switch (priority)
- {
- case G_THREAD_PRIORITY_LOW:
- return PRIORITY_LOW_VALUE;
-
- case G_THREAD_PRIORITY_NORMAL:
- return PRIORITY_NORMAL_VALUE;
-
- case G_THREAD_PRIORITY_HIGH:
- return PRIORITY_HIGH_VALUE;
-
- case G_THREAD_PRIORITY_URGENT:
- return PRIORITY_URGENT_VALUE;
+typedef struct
+{
+ GRealThread thread;
- default:
- g_assert_not_reached ();
- }
-}
+ pthread_t system_thread;
+ gboolean joined;
+ GMutex lock;
+} GThreadPosix;
-#endif /* POSIX_MIN_PRIORITY && POSIX_MAX_PRIORITY */
+void
+g_system_thread_free (GRealThread *thread)
+{
+ GThreadPosix *pt = (GThreadPosix *) thread;
-static gulong g_thread_min_stack_size = 0;
+ if (!pt->joined)
+ pthread_detach (pt->system_thread);
-#define G_MUTEX_SIZE (sizeof (pthread_mutex_t))
+ g_mutex_clear (&pt->lock);
-void
-_g_thread_impl_init(void)
-{
-#ifdef _SC_THREAD_STACK_MIN
- g_thread_min_stack_size = MAX (sysconf (_SC_THREAD_STACK_MIN), 0);
-#endif /* _SC_THREAD_STACK_MIN */
-#ifdef HAVE_PRIORITIES
- {
- struct sched_param sched;
- int policy;
- posix_check_cmd (pthread_getschedparam (pthread_self(), &policy, &sched));
- priority_normal_value = sched.sched_priority;
- }
-#endif /* HAVE_PRIORITIES */
+ g_slice_free (GThreadPosix, pt);
}
-static void
-g_thread_create_posix_impl (GThreadFunc thread_func,
- gpointer arg,
- gulong stack_size,
- gboolean joinable,
- gboolean bound,
- GThreadPriority priority,
- gpointer thread,
- GError **error)
+GRealThread *
+g_system_thread_new (GThreadFunc thread_func,
+ gulong stack_size,
+ GError **error)
{
+ GThreadPosix *thread;
pthread_attr_t attr;
gint ret;
- g_return_if_fail (thread_func);
- g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
- g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
+ thread = g_slice_new0 (GThreadPosix);
posix_check_cmd (pthread_attr_init (&attr));
#ifdef HAVE_PTHREAD_ATTR_SETSTACKSIZE
if (stack_size)
{
- stack_size = MAX (g_thread_min_stack_size, stack_size);
+#ifdef _SC_THREAD_STACK_MIN
+ stack_size = MAX (sysconf (_SC_THREAD_STACK_MIN), stack_size);
+#endif /* _SC_THREAD_STACK_MIN */
/* No error check here, because some systems can't do it and
* we simply don't want threads to fail because of that. */
pthread_attr_setstacksize (&attr, stack_size);
}
#endif /* HAVE_PTHREAD_ATTR_SETSTACKSIZE */
-#ifdef PTHREAD_SCOPE_SYSTEM
- if (bound)
- /* No error check here, because some systems can't do it and we
- * simply don't want threads to fail because of that. */
- pthread_attr_setscope (&attr, PTHREAD_SCOPE_SYSTEM);
-#endif /* PTHREAD_SCOPE_SYSTEM */
-
- posix_check_cmd (pthread_attr_setdetachstate (&attr,
- joinable ? PTHREAD_CREATE_JOINABLE : PTHREAD_CREATE_DETACHED));
-
-#ifdef HAVE_PRIORITIES
- {
- struct sched_param sched;
- posix_check_cmd (pthread_attr_getschedparam (&attr, &sched));
- sched.sched_priority = g_thread_priority_map (priority);
- posix_check_cmd_prio (pthread_attr_setschedparam (&attr, &sched));
- }
-#endif /* HAVE_PRIORITIES */
- ret = pthread_create (thread, &attr, (void* (*)(void*))thread_func, arg);
+ ret = pthread_create (&thread->system_thread, &attr, (void* (*)(void*))thread_func, thread);
posix_check_cmd (pthread_attr_destroy (&attr));
if (ret == EAGAIN)
{
g_set_error (error, G_THREAD_ERROR, G_THREAD_ERROR_AGAIN,
- "Error creating thread: %s", g_strerror (ret));
- return;
+ "Error creating thread: %s", g_strerror (ret));
+ g_slice_free (GThreadPosix, thread);
+ return NULL;
}
posix_check_err (ret, "pthread_create");
+
+ g_mutex_init (&thread->lock);
+
+ return (GRealThread *) thread;
}
-static void
-g_thread_yield_posix_impl (void)
+/**
+ * g_thread_yield:
+ *
+ * Causes the calling thread to voluntarily relinquish the CPU, so
+ * that other threads can run.
+ *
+ * This function is often used as a method to make busy wait less evil.
+ */
+void
+g_thread_yield (void)
{
- POSIX_YIELD_FUNC;
+ sched_yield ();
}
-static void
-g_thread_join_posix_impl (gpointer thread)
+void
+g_system_thread_wait (GRealThread *thread)
{
- gpointer ignore;
- posix_check_cmd (pthread_join (*(pthread_t*)thread, &ignore));
+ GThreadPosix *pt = (GThreadPosix *) thread;
+
+ g_mutex_lock (&pt->lock);
+
+ if (!pt->joined)
+ {
+ posix_check_cmd (pthread_join (pt->system_thread, NULL));
+ pt->joined = TRUE;
+ }
+
+ g_mutex_unlock (&pt->lock);
}
-static void
-g_thread_exit_posix_impl (void)
+void
+g_system_thread_exit (void)
{
pthread_exit (NULL);
}
-static void
-g_thread_set_priority_posix_impl (gpointer thread, GThreadPriority priority)
+void
+g_system_thread_set_name (const gchar *name)
{
- g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
- g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
-#ifdef HAVE_PRIORITIES
- {
- struct sched_param sched;
- int policy;
- posix_check_cmd (pthread_getschedparam (*(pthread_t*)thread, &policy,
- &sched));
- sched.sched_priority = g_thread_priority_map (priority);
- posix_check_cmd_prio (pthread_setschedparam (*(pthread_t*)thread, policy,
- &sched));
- }
-#endif /* HAVE_PRIORITIES */
+#ifdef HAVE_SYS_PRCTL_H
+#ifdef PR_SET_NAME
+ prctl (PR_SET_NAME, name, 0, 0, 0, 0);
+#endif
+#endif
}
-static void
-g_thread_self_posix_impl (gpointer thread)
-{
- *(pthread_t*)thread = pthread_self();
-}
-
-static gboolean
-g_thread_equal_posix_impl (gpointer thread1, gpointer thread2)
-{
- return (pthread_equal (*(pthread_t*)thread1, *(pthread_t*)thread2) != 0);
-}
-
-/* {{{1 Epilogue */
-GThreadFunctions g_thread_functions_for_glib_use =
-{
- g_mutex_new,
- g_mutex_lock,
- g_mutex_trylock,
- g_mutex_unlock,
- g_mutex_free,
- g_cond_new,
- g_cond_signal,
- g_cond_broadcast,
- g_cond_wait,
- g_cond_timed_wait,
- g_cond_free,
- g_private_new,
- g_private_get,
- g_private_set,
- g_thread_create_posix_impl,
- g_thread_yield_posix_impl,
- g_thread_join_posix_impl,
- g_thread_exit_posix_impl,
- g_thread_set_priority_posix_impl,
- g_thread_self_posix_impl,
- g_thread_equal_posix_impl
-};
+/* {{{1 GMutex and GCond futex implementation */
+
+#if defined(USE_NATIVE_MUTEX)
+
+#include
+#include
+
+/* We should expand the set of operations available in gatomic once we
+ * have better C11 support in GCC in common distributions (ie: 4.9).
+ *
+ * Before then, let's define a couple of useful things for our own
+ * purposes...
+ */
+
+#define exchange_acquire(ptr, new) \
+ __atomic_exchange_4((ptr), (new), __ATOMIC_ACQUIRE)
+#define compare_exchange_acquire(ptr, old, new) \
+ __atomic_compare_exchange_4((ptr), (old), (new), 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)
+
+#define exchange_release(ptr, new) \
+ __atomic_exchange_4((ptr), (new), __ATOMIC_RELEASE)
+#define store_release(ptr, new) \
+ __atomic_store_4((ptr), (new), __ATOMIC_RELEASE)
+
+/* Our strategy for the mutex is pretty simple:
+ *
+ * 0: not in use
+ *
+ * 1: acquired by one thread only, no contention
+ *
+ * > 1: contended
+ *
+ *
+ * As such, attempting to acquire the lock should involve an increment.
+ * If we find that the previous value was 0 then we can return
+ * immediately.
+ *
+ * On unlock, we always store 0 to indicate that the lock is available.
+ * If the value there was 1 before then we didn't have contention and
+ * can return immediately. If the value was something other than 1 then
+ * we have the contended case and need to wake a waiter.
+ *
+ * If it was not 0 then there is another thread holding it and we must
+ * wait. We must always ensure that we mark a value >1 while we are
+ * waiting in order to instruct the holder to do a wake operation on
+ * unlock.
+ */
+
+void
+g_mutex_init (GMutex *mutex)
+{
+ mutex->i[0] = 0;
+}
+
+void
+g_mutex_clear (GMutex *mutex)
+{
+ if G_UNLIKELY (mutex->i[0] != 0)
+ {
+ fprintf (stderr, "g_mutex_clear() called on uninitialised or locked mutex\n");
+ abort ();
+ }
+}
+
+static void __attribute__((noinline))
+g_mutex_lock_slowpath (GMutex *mutex)
+{
+ /* Set to 2 to indicate contention. If it was zero before then we
+ * just acquired the lock.
+ *
+ * Otherwise, sleep for as long as the 2 remains...
+ */
+ while (exchange_acquire (&mutex->i[0], 2) != 0)
+ syscall (__NR_futex, &mutex->i[0], (gsize) FUTEX_WAIT, (gsize) 2, NULL);
+}
+
+static void __attribute__((noinline))
+g_mutex_unlock_slowpath (GMutex *mutex,
+ guint prev)
+{
+ /* We seem to get better code for the uncontended case by splitting
+ * this out...
+ */
+ if G_UNLIKELY (prev == 0)
+ {
+ fprintf (stderr, "Attempt to unlock mutex that was not locked\n");
+ abort ();
+ }
+
+ syscall (__NR_futex, &mutex->i[0], (gsize) FUTEX_WAKE, (gsize) 1, NULL);
+}
+
+void
+g_mutex_lock (GMutex *mutex)
+{
+ /* 0 -> 1 and we're done. Anything else, and we need to wait... */
+ if G_UNLIKELY (g_atomic_int_add (&mutex->i[0], 1) != 0)
+ g_mutex_lock_slowpath (mutex);
+}
+
+void
+g_mutex_unlock (GMutex *mutex)
+{
+ guint prev;
+
+ prev = exchange_release (&mutex->i[0], 0);
+
+ /* 1-> 0 and we're done. Anything else and we need to signal... */
+ if G_UNLIKELY (prev != 1)
+ g_mutex_unlock_slowpath (mutex, prev);
+}
+
+gboolean
+g_mutex_trylock (GMutex *mutex)
+{
+ guint zero = 0;
+
+ /* We don't want to touch the value at all unless we can move it from
+ * exactly 0 to 1.
+ */
+ return compare_exchange_acquire (&mutex->i[0], &zero, 1);
+}
+
+/* Condition variables are implemented in a rather simple way as well.
+ * In many ways, futex() as an abstraction is even more ideally suited
+ * to condition variables than it is to mutexes.
+ *
+ * We store a generation counter. We sample it with the lock held and
+ * unlock before sleeping on the futex.
+ *
+ * Signalling simply involves increasing the counter and making the
+ * appropriate futex call.
+ *
+ * The only thing that is the slightest bit complicated is timed waits
+ * because we must convert our absolute time to relative.
+ */
+
+void
+g_cond_init (GCond *cond)
+{
+ cond->i[0] = 0;
+}
+
+void
+g_cond_clear (GCond *cond)
+{
+}
+
+void
+g_cond_wait (GCond *cond,
+ GMutex *mutex)
+{
+ guint sampled = g_atomic_int_get (&cond->i[0]);
+
+ g_mutex_unlock (mutex);
+ syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT, (gsize) sampled, NULL);
+ g_mutex_lock (mutex);
+}
+
+void
+g_cond_signal (GCond *cond)
+{
+ g_atomic_int_inc (&cond->i[0]);
+
+ syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAKE, (gsize) 1, NULL);
+}
+
+void
+g_cond_broadcast (GCond *cond)
+{
+ g_atomic_int_inc (&cond->i[0]);
+
+ syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAKE, (gsize) INT_MAX, NULL);
+}
+
+gboolean
+g_cond_wait_until (GCond *cond,
+ GMutex *mutex,
+ gint64 end_time)
+{
+ struct timespec now;
+ struct timespec span;
+ guint sampled;
+ int res;
+
+ if (end_time < 0)
+ return FALSE;
+
+ clock_gettime (CLOCK_MONOTONIC, &now);
+ span.tv_sec = (end_time / 1000000) - now.tv_sec;
+ span.tv_nsec = ((end_time % 1000000) * 1000) - now.tv_nsec;
+ if (span.tv_nsec < 0)
+ {
+ span.tv_nsec += 1000000000;
+ span.tv_sec--;
+ }
+
+ if (span.tv_sec < 0)
+ return FALSE;
+
+ sampled = cond->i[0];
+ g_mutex_unlock (mutex);
+ res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT, (gsize) sampled, &span);
+ g_mutex_lock (mutex);
+
+ return (res < 0 && errno == ETIMEDOUT) ? FALSE : TRUE;
+}
+
+#endif
+ /* {{{1 Epilogue */
/* vim:set foldmethod=marker: */