* 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 <http://www.gnu.org/licenses/>.
*/
/*
#include "gslice.h"
#include "gmessages.h"
#include "gstrfuncs.h"
+#include "gmain.h"
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <pthread.h>
-#ifdef HAVE_SYS_TIME_H
-# include <sys/time.h>
-#endif
-#ifdef HAVE_UNISTD_H
-# include <unistd.h>
-#endif
+#include <sys/time.h>
+#include <unistd.h>
+
#ifdef HAVE_SCHED_H
#include <sched.h>
#endif
#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#endif
+#ifdef G_OS_WIN32
+#include <windows.h>
+#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 */
+#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");
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
- pthread_mutexattr_t attr;
pthread_mutexattr_init (&attr);
pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
pattr = &attr;
free (mutex);
}
-static pthread_mutex_t *
+static inline pthread_mutex_t *
g_mutex_get_impl (GMutex *mutex)
{
- pthread_mutex_t *impl = mutex->p;
+ pthread_mutex_t *impl = g_atomic_pointer_get (&mutex->p);
if G_UNLIKELY (impl == NULL)
{
* 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
- * created that has been statically allocated.
+ * statically allocated.
*
- * |[
+ * |[<!-- language="C" -->
* typedef struct {
* GMutex m;
* ...
* current thread will block until @mutex is unlocked by the other
* thread.
*
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will do nothing.
- *
- * <note>#GMutex is neither guaranteed to be recursive nor to be
+ * #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).</note>
+ * (including but not limited to deadlocks).
*/
void
g_mutex_lock (GMutex *mutex)
*
* Calling g_mutex_unlock() on a mutex that is not locked by the
* current thread leads to undefined behaviour.
- *
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will do nothing.
*/
void
g_mutex_unlock (GMutex *mutex)
gint status;
if G_UNLIKELY ((status = pthread_mutex_unlock (g_mutex_get_impl (mutex))) != 0)
- g_thread_abort (status, "pthread_mutex_lock");
+ g_thread_abort (status, "pthread_mutex_unlock");
}
/**
* it immediately returns %FALSE. Otherwise it locks @mutex and returns
* %TRUE.
*
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will immediately return %TRUE.
- *
- * <note>#GMutex is neither guaranteed to be recursive nor to be
+ * #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).
- * </note>
* Returns: %TRUE if @mutex could be locked
*/
return FALSE;
}
+#endif /* !defined(USE_NATIVE_MUTEX) */
+
/* {{{1 GRecMutex */
static pthread_mutex_t *
pthread_mutexattr_t attr;
pthread_mutex_t *mutex;
- mutex = g_slice_new (pthread_mutex_t);
+ 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);
g_rec_mutex_impl_free (pthread_mutex_t *mutex)
{
pthread_mutex_destroy (mutex);
- g_slice_free (pthread_mutex_t, mutex);
+ free (mutex);
}
-static pthread_mutex_t *
+static inline pthread_mutex_t *
g_rec_mutex_get_impl (GRecMutex *rec_mutex)
{
- pthread_mutex_t *impl = rec_mutex->p;
+ pthread_mutex_t *impl = g_atomic_pointer_get (&rec_mutex->p);
if G_UNLIKELY (impl == NULL)
{
* It is not necessary to initialise a recursive mutex that has been
* statically allocated.
*
- * |[
+ * |[<!-- language="C" -->
* typedef struct {
* GRecMutex m;
* ...
/**
* g_rec_mutex_unlock:
- * @rec_mutex: a #RecGMutex
+ * @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
free (rwlock);
}
-static pthread_rwlock_t *
+static inline pthread_rwlock_t *
g_rw_lock_get_impl (GRWLock *lock)
{
- pthread_rwlock_t *impl = lock->p;
+ pthread_rwlock_t *impl = g_atomic_pointer_get (&lock->p);
if G_UNLIKELY (impl == NULL)
{
* necessary to initialise a reader-writer lock that has been statically
* allocated.
*
- * |[
+ * |[<!-- language="C" -->
* typedef struct {
* GRWLock l;
* ...
/* {{{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, NULL)) != 0)
+ if G_UNLIKELY ((status = pthread_cond_init (cond, &attr)) != 0)
g_thread_abort (status, "pthread_cond_init");
+ pthread_condattr_destroy (&attr);
+
return cond;
}
free (cond);
}
-static pthread_cond_t *
+static inline pthread_cond_t *
g_cond_get_impl (GCond *cond)
{
- pthread_cond_t *impl = cond->p;
+ pthread_cond_t *impl = g_atomic_pointer_get (&cond->p);
if G_UNLIKELY (impl == NULL)
{
* g_cond_init:
* @cond: an uninitialized #GCond
*
- * Initialized a #GCond so that it can be used.
+ * Initialises a #GCond so that it can be used.
*
- * This function is useful to initialize a #GCond that has been
- * allocated on the stack, or as part of a larger structure.
- * It is not necessary to initialize a #GCond that has been
- * statically allocated.
+ * 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 initialized #GCond leads
+ * Calling g_cond_init() on an already-initialised #GCond leads
* to undefined behaviour.
*
* Since: 2.32
/**
* g_cond_clear:
- * @cond: an initialized #GCond
+ * @cond: an initialised #GCond
*
* Frees the resources allocated to a #GCond with g_cond_init().
*
* @cond: a #GCond
* @mutex: a #GMutex that is currently locked
*
- * Waits until this thread is woken up on @cond. The @mutex is unlocked
- * before falling asleep and locked again before resuming.
+ * Atomically releases @mutex and waits until @cond is signalled.
+ * When this function returns, @mutex is locked again and owned by the
+ * calling thread.
*
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will immediately return.
- */
+ * 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)
* 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.
- *
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will do nothing.
*/
void
g_cond_signal (GCond *cond)
* 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.
- *
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will do nothing.
*/
void
g_cond_broadcast (GCond *cond)
}
/**
- * g_cond_timed_wait:
+ * g_cond_wait_until:
* @cond: a #GCond
* @mutex: a #GMutex that is currently locked
- * @abs_time: a #GTimeVal, determining the final time
+ * @end_time: the monotonic time to wait until
*
- * Waits until this thread is woken up on @cond, but not longer than
- * until the time specified by @abs_time. The @mutex is unlocked before
- * falling asleep and locked again before resuming.
+ * Waits until either @cond is signalled or @end_time has passed.
*
- * If @abs_time is %NULL, g_cond_timed_wait() acts like g_cond_wait().
+ * 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.
*
- * This function can be used even if g_thread_init() has not yet been
- * called, and, in that case, will immediately return %TRUE.
+ * %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.
*
- * To easily calculate @abs_time a combination of g_get_current_time()
- * and g_time_val_add() can be used.
+ * The following code shows how to correctly perform a timed wait on a
+ * condition variable (extending the example presented in the
+ * documentation for #GCond):
*
- * Returns: %TRUE if @cond was signalled, or %FALSE on timeout
- */
-gboolean
-g_cond_timed_wait (GCond *cond,
- GMutex *mutex,
- GTimeVal *abs_time)
-{
- struct timespec end_time;
- 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 (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &end_time)) == 0)
- return TRUE;
-
- if G_UNLIKELY (status != ETIMEDOUT)
- g_thread_abort (status, "pthread_cond_timedwait");
-
- return FALSE;
-}
-
-/**
- * g_cond_timedwait:
- * @cond: a #GCond
- * @mutex: a #GMutex that is currently locked
- * @abs_time: the final time, in microseconds
+ * |[<!-- language="C" -->
+ * 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;
+ * }
*
- * A variant of g_cond_timed_wait() that takes @abs_time
- * as a #gint64 instead of a #GTimeVal.
- * See g_cond_timed_wait() for details.
+ * // there is data for us
+ * data = current_data;
+ * current_data = NULL;
*
- * Returns: %TRUE if @cond was signalled, or %FALSE on timeout
+ * 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_timedwait (GCond *cond,
- GMutex *mutex,
- gint64 abs_time)
+g_cond_wait_until (GCond *cond,
+ GMutex *mutex,
+ gint64 end_time)
{
- struct timespec end_time;
+ struct timespec ts;
gint status;
- end_time.tv_sec = abs_time / 1000000;
- end_time.tv_nsec = (abs_time % 1000000) * 1000;
+#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 ((status = pthread_cond_timedwait (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &end_time)) == 0)
- return TRUE;
+ if (end_time <= now)
+ return FALSE;
+
+ relative = end_time - now;
+
+ ts.tv_sec = relative / 1000000;
+ ts.tv_nsec = (relative % 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 (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");
return FALSE;
}
+#endif /* defined(USE_NATIVE_MUTEX) */
+
/* {{{1 GPrivate */
/**
* See G_PRIVATE_INIT() for a couple of examples.
*
* The #GPrivate structure should be considered opaque. It should only
- * be accessed via the <function>g_private_</function> functions.
+ * be accessed via the g_private_ functions.
*/
/**
* be properly initialised by default (ie: to all zeros). See the
* examples below.
*
- * |[
+ * |[<!-- language="C" -->
* static GPrivate name_key = G_PRIVATE_INIT (g_free);
*
* // return value should not be freed
free (key);
}
-static pthread_key_t *
+static inline pthread_key_t *
g_private_get_impl (GPrivate *key)
{
- pthread_key_t *impl = key->p;
+ pthread_key_t *impl = g_atomic_pointer_get (&key->p);
if G_UNLIKELY (impl == NULL)
{
#define posix_check_cmd(cmd) posix_check_err (cmd, #cmd)
-GRealThread *
-g_system_thread_new (void)
+typedef struct
{
- return g_slice_new0 (GRealThread);
-}
+ GRealThread thread;
+
+ pthread_t system_thread;
+ gboolean joined;
+ GMutex lock;
+} GThreadPosix;
void
g_system_thread_free (GRealThread *thread)
{
- g_slice_free (GRealThread, thread);
+ GThreadPosix *pt = (GThreadPosix *) thread;
+
+ if (!pt->joined)
+ pthread_detach (pt->system_thread);
+
+ g_mutex_clear (&pt->lock);
+
+ g_slice_free (GThreadPosix, pt);
}
-void
-g_system_thread_create (GThreadFunc thread_func,
- gpointer arg,
- gulong stack_size,
- gboolean joinable,
- GRealThread *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);
+ thread = g_slice_new0 (GThreadPosix);
posix_check_cmd (pthread_attr_init (&attr));
}
#endif /* HAVE_PTHREAD_ATTR_SETSTACKSIZE */
- posix_check_cmd (pthread_attr_setdetachstate (&attr,
- joinable ? PTHREAD_CREATE_JOINABLE : PTHREAD_CREATE_DETACHED));
-
- ret = pthread_create ((pthread_t *) &(thread->system_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;
}
/**
void
g_system_thread_wait (GRealThread *thread)
{
- gpointer ignore;
- posix_check_cmd (pthread_join (*(pthread_t*)&(thread->system_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);
}
void
g_system_thread_set_name (const gchar *name)
{
#ifdef HAVE_SYS_PRCTL_H
+#ifdef PR_SET_NAME
prctl (PR_SET_NAME, name, 0, 0, 0, 0);
#endif
+#endif
+}
+
+/* {{{1 GMutex and GCond futex implementation */
+
+#if defined(USE_NATIVE_MUTEX)
+
+#include <linux/futex.h>
+#include <sys/syscall.h>
+
+/* 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);
}
-/* {{{1 Epilogue */
+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: */