/* GLIB - Library of useful routines for C programming

 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald

 *

 * gthread.c: posix thread system implementation

 * Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * 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, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/.

 */

/* The GMutex, GCond and GPrivate implementations in this file are some

 * of the lowest-level code in GLib.  All other parts of GLib (messages,

 * memory, slices, etc) assume that they can freely use these facilities

 * without risking recursion.

 *

 * As such, these functions are NOT permitted to call any other part of

 * GLib.

 *

 * The thread manipulation functions (create, exit, join, etc.) have

 * more freedom -- they can do as they please.

 */

#include "config.h"

#include "gthread.h"

#include "gthreadprivate.h"

#include "gslice.h"

#include "gmessages.h"

#include "gstrfuncs.h"

#include "gmain.h"

#include "gutils.h"

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <pthread.h>

#include <sys/time.h>

#include <unistd.h>

#ifdef HAVE_SCHED_H

#include <sched.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",

           function, strerror (status));

  g_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_init (&attr);

  pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ADAPTIVE_NP);

  pattr = &att;;

#endif

  if G_UNLIKELY ((status = pthread_mutex_init (mutex, pattr)) != 0)

    g_thread_abort (status, "pthread_mutex_init");

#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_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_init (GMutex *mutex)

{

  mutex->p = g_mutex_impl_new ();

}

/**

 * 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 (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 (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 (g_mutex_get_impl (mutex))) == 0)

    return TRUE;

  if G_UNLIKELY (status != EBUSY)

    g_thread_abort (status, "pthread_mutex_trylock");

  return FALSE;

}

#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_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;

  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)

{

  int retval = pthread_rwlock_wrlock (g_rw_lock_get_impl (rw_lock));

  if (retval != 0)

    g_critical ("Failed to get RW lock %p: %s", rw_lock, g_strerror (retval));

}

/**

 * 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. If the limit is hit,

 * or if a deadlock is detected, a critical warning will be emitted.

 *

 * Since: 2.32

 */

void

g_rw_lock_reader_lock (GRWLock *rw_lock)

{

  int retval = pthread_rwlock_rdlock (g_rw_lock_get_impl (rw_lock));

  if (retval != 0)

    g_critical ("Failed to get RW lock %p: %s", rw_lock, g_strerror (retval));

}

/**

 * 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)

{

  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 (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 (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 (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_wait_until (GCond  *cond,

                   GMutex *mutex,

                   gint64  end_time)

{

  struct timespec ts;

  gint status;

#ifdef HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP

  /* end_time is given relative to the monotonic clock as returned by

   * g_get_monotonic_time().