glib/gthreadpool.c - third_party/glib - Git at Google

 /* GLIB - Library of useful routines for C programming
  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
  *
  * GAsyncQueue: thread pool implementation.
  * Copyright (C) 2000 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 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, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */

 /*
  * MT safe
  */

 #include "config.h"

 #include "galias.h"
 #include "glib.h"


 typedef struct _GRealThreadPool GRealThreadPool;

 struct _GRealThreadPool
 {
   GThreadPool pool;
   GAsyncQueue* queue;
   gint max_threads;
   gint num_threads;
   gboolean running;
   gboolean immediate;
   gboolean waiting;
 };

 /* The following is just an address to mark the stop order for a
  * thread, it could be any address (as long, as it isn't a valid
  * GThreadPool address) */
 static const gpointer stop_this_thread_marker = (gpointer) &g_thread_pool_new;

 /* Here all unused threads are waiting  */
 static GAsyncQueue *unused_thread_queue;
 static gint unused_threads = 0;
 static gint max_unused_threads = 0;
 G_LOCK_DEFINE_STATIC (unused_threads);

 static GMutex *inform_mutex = NULL;
 static GCond *inform_cond = NULL;

 static void     g_thread_pool_free_internal (GRealThreadPool* pool);
 static gpointer g_thread_pool_thread_proxy (gpointer data);
 static void     g_thread_pool_start_thread (GRealThreadPool* pool,
 					    GError **error);
 static void     g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool);

 #define g_thread_should_run(pool, len) \
   ((pool)->running || (!(pool)->immediate && (len) > 0))

 static gpointer
 g_thread_pool_thread_proxy (gpointer data)
 {
   GRealThreadPool *pool = data;
   gboolean watcher = FALSE;

   g_async_queue_lock (pool->queue);
   while (TRUE)
     {
       gpointer task;
       gboolean goto_global_pool = !pool->pool.exclusive;
       gint len = g_async_queue_length_unlocked (pool->queue);

       if (g_thread_should_run (pool, len))
 	{
 	  if (watcher)
 	    {
 	      /* This thread is actually not needed here, but it waits
                * for some time anyway. If during that time a new
                * request arrives, this saves process
                * swicthes. Otherwise the thread will go to the global
                * pool afterwards */
 	      GTimeVal end_time;
 	      g_get_current_time (&end_time);
 	      g_time_val_add (&end_time, G_USEC_PER_SEC / 2); /* 1/2 second */
 	      task = g_async_queue_timed_pop_unlocked (pool->queue, &end_time);
 	    }
 	  else
 	    task = g_async_queue_pop_unlocked (pool->queue);

 	  if (task)
 	    {
 	      watcher = FALSE;
 	      if (pool->num_threads > pool->max_threads &&
 		  pool->max_threads != -1)
 		/* We are in fact a superfluous threads, so we go to
 		 * the global pool and just hand the data further to
 		 * the next one waiting in the queue */
 		{
 		  g_async_queue_push_unlocked (pool->queue, task);
 		  goto_global_pool = TRUE;
 		}
 	      else if (pool->running || !pool->immediate)
 		{
 		  g_async_queue_unlock (pool->queue);
 		  pool->pool.func (task, pool->pool.user_data);
 		  g_async_queue_lock (pool->queue);
 		}
 	    }
 	  len = g_async_queue_length_unlocked (pool->queue);
 	}

       if (!g_thread_should_run (pool, len))
 	{
 	  g_cond_broadcast (inform_cond);
 	  goto_global_pool = TRUE;
 	}
       else if (len > 0)
 	{
 	  /* At this pool there are no threads waiting, but tasks are. */
 	  goto_global_pool = FALSE;
 	}
       else if (len == 0 && !watcher && !pool->pool.exclusive)
 	{
 	  /* Here neither threads nor tasks are queued and we didn't
 	   * just return from a timed wait. We now wait for a limited
 	   * time at this pool for new tasks to avoid costly context
 	   * switches. */
 	  goto_global_pool = FALSE;
 	  watcher = TRUE;
 	}

       if (goto_global_pool)
 	{
 	  pool->num_threads--;

 	  if (!pool->running && !pool->waiting)
 	    {
 	      if (pool->num_threads == 0)
 		{
 		  g_async_queue_unlock (pool->queue);
 		  g_thread_pool_free_internal (pool);
 		}
 	      else
 		{
 		  if (len == - pool->num_threads)
 		    g_thread_pool_wakeup_and_stop_all (pool);

 		  g_async_queue_unlock (pool->queue);
 		}
 	    }
 	  else
 	    g_async_queue_unlock (pool->queue);

 	  g_async_queue_lock (unused_thread_queue);

 	  G_LOCK (unused_threads);
 	  if ((unused_threads >= max_unused_threads &&
 	       max_unused_threads != -1))
 	    {
 	      G_UNLOCK (unused_threads);
 	      g_async_queue_unlock (unused_thread_queue);
 	      /* Stop this thread */
 	      return NULL;
 	    }
 	  unused_threads++;
 	  G_UNLOCK (unused_threads);

 	  pool = g_async_queue_pop_unlocked (unused_thread_queue);

 	  G_LOCK (unused_threads);
 	  unused_threads--;
 	  G_UNLOCK (unused_threads);

 	  g_async_queue_unlock (unused_thread_queue);

 	  if (pool == stop_this_thread_marker)
 	    /* Stop this thread */
 	    return NULL;

 	  g_async_queue_lock (pool->queue);

 	  /* pool->num_threads++ is not done here, but in
            * g_thread_pool_start_thread to make the new started thread
            * known to the pool, before itself can do it. */
 	}
     }
   return NULL;
 }

 static void
 g_thread_pool_start_thread (GRealThreadPool  *pool,
 			    GError          **error)
 {
   gboolean success = FALSE;

   if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
     /* Enough threads are already running */
     return;

   g_async_queue_lock (unused_thread_queue);

   if (g_async_queue_length_unlocked (unused_thread_queue) < 0)
     {
       g_async_queue_push_unlocked (unused_thread_queue, pool);
       success = TRUE;
     }

   g_async_queue_unlock (unused_thread_queue);

   if (!success)
     {
       GError *local_error = NULL;
       /* No thread was found, we have to start a new one */
       g_thread_create (g_thread_pool_thread_proxy, pool, FALSE, &local_error);

       if (local_error)
 	{
 	  g_propagate_error (error, local_error);
 	  return;
 	}
     }

   /* See comment in g_thread_pool_thread_proxy as to why this is done
    * here and not there */
   pool->num_threads++;
 }

 /**
  * g_thread_pool_new:
  * @func: a function to execute in the threads of the new thread pool
  * @user_data: user data that is handed over to @func every time it
  *   is called
  * @max_threads: the maximal number of threads to execute concurrently in
  *   the new thread pool, -1 means no limit
  * @exclusive: should this thread pool be exclusive?
  * @error: return location for error
  *
  * This function creates a new thread pool.
  *
  * Whenever you call g_thread_pool_push(), either a new thread is
  * created or an unused one is reused. At most @max_threads threads
  * are running concurrently for this thread pool. @max_threads = -1
  * allows unlimited threads to be created for this thread pool. The
  * newly created or reused thread now executes the function @func with
  * the two arguments. The first one is the parameter to
  * g_thread_pool_push() and the second one is @user_data.
  *
  * The parameter @exclusive determines, whether the thread pool owns
  * all threads exclusive or whether the threads are shared
  * globally. If @exclusive is %TRUE, @max_threads threads are started
  * immediately and they will run exclusively for this thread pool until
  * it is destroyed by g_thread_pool_free(). If @exclusive is %FALSE,
  * threads are created, when needed and shared between all
  * non-exclusive thread pools. This implies that @max_threads may not
  * be -1 for exclusive thread pools.
  *
  * @error can be %NULL to ignore errors, or non-%NULL to report
  * errors. An error can only occur when @exclusive is set to %TRUE and
  * not all @max_threads threads could be created.
  *
  * Return value: the new #GThreadPool
  **/
 GThreadPool*
 g_thread_pool_new (GFunc            func,
 		   gpointer         user_data,
 		   gint             max_threads,
 		   gboolean         exclusive,
 		   GError         **error)
 {
   GRealThreadPool *retval;
   G_LOCK_DEFINE_STATIC (init);

   g_return_val_if_fail (func, NULL);
   g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
   g_return_val_if_fail (max_threads >= -1, NULL);
   g_return_val_if_fail (g_thread_supported (), NULL);

   retval = g_new (GRealThreadPool, 1);

   retval->pool.func = func;
   retval->pool.user_data = user_data;
   retval->pool.exclusive = exclusive;
   retval->queue = g_async_queue_new ();
   retval->max_threads = max_threads;
   retval->num_threads = 0;
   retval->running = TRUE;

   G_LOCK (init);

   if (!inform_mutex)
     {
       inform_mutex = g_mutex_new ();
       inform_cond = g_cond_new ();
       unused_thread_queue = g_async_queue_new ();
     }

   G_UNLOCK (init);

   if (retval->pool.exclusive)
     {
       g_async_queue_lock (retval->queue);

       while (retval->num_threads < retval->max_threads)
 	{
 	  GError *local_error = NULL;
 	  g_thread_pool_start_thread (retval, &local_error);
 	  if (local_error)
 	    {
 	      g_propagate_error (error, local_error);
 	      break;
 	    }
 	}

       g_async_queue_unlock (retval->queue);
     }

   return (GThreadPool*) retval;
 }

 /**
  * g_thread_pool_push:
  * @pool: a #GThreadPool
  * @data: a new task for @pool
  * @error: return location for error
  *
  * Inserts @data into the list of tasks to be executed by @pool. When
  * the number of currently running threads is lower than the maximal
  * allowed number of threads, a new thread is started (or reused) with
  * the properties given to g_thread_pool_new (). Otherwise @data stays
  * in the queue until a thread in this pool finishes its previous task
  * and processes @data.
  *
  * @error can be %NULL to ignore errors, or non-%NULL to report
  * errors. An error can only occur when a new thread couldn't be
  * created. In that case @data is simply appended to the queue of work
  * to do.
  **/
 void
 g_thread_pool_push (GThreadPool     *pool,
 		    gpointer         data,
 		    GError         **error)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;

   g_return_if_fail (real);

   g_async_queue_lock (real->queue);

   if (!real->running)
     {
       g_async_queue_unlock (real->queue);
       g_return_if_fail (real->running);
     }

   if (g_async_queue_length_unlocked (real->queue) >= 0)
     /* No thread is waiting in the queue */
     g_thread_pool_start_thread (real, error);

   g_async_queue_push_unlocked (real->queue, data);
   g_async_queue_unlock (real->queue);
 }

 /**
  * g_thread_pool_set_max_threads:
  * @pool: a #GThreadPool
  * @max_threads: a new maximal number of threads for @pool
  * @error: return location for error
  *
  * Sets the maximal allowed number of threads for @pool. A value of -1
  * means, that the maximal number of threads is unlimited.
  *
  * Setting @max_threads to 0 means stopping all work for @pool. It is
  * effectively frozen until @max_threads is set to a non-zero value
  * again.
  *
  * A thread is never terminated while calling @func, as supplied by
  * g_thread_pool_new (). Instead the maximal number of threads only
  * has effect for the allocation of new threads in g_thread_pool_push().
  * A new thread is allocated, whenever the number of currently
  * running threads in @pool is smaller than the maximal number.
  *
  * @error can be %NULL to ignore errors, or non-%NULL to report
  * errors. An error can only occur when a new thread couldn't be
  * created.
  **/
 void
 g_thread_pool_set_max_threads (GThreadPool     *pool,
 			       gint             max_threads,
 			       GError         **error)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;
   gint to_start;

   g_return_if_fail (real);
   g_return_if_fail (real->running);
   g_return_if_fail (!real->pool.exclusive || max_threads != -1);
   g_return_if_fail (max_threads >= -1);

   g_async_queue_lock (real->queue);

   real->max_threads = max_threads;

   if (pool->exclusive)
     to_start = real->max_threads - real->num_threads;
   else
     to_start = g_async_queue_length_unlocked (real->queue);

   for ( ; to_start > 0; to_start--)
     {
       GError *local_error = NULL;
       g_thread_pool_start_thread (real, &local_error);
       if (local_error)
 	{
 	  g_propagate_error (error, local_error);
 	  break;
 	}
     }

   g_async_queue_unlock (real->queue);
 }

 /**
  * g_thread_pool_get_max_threads:
  * @pool: a #GThreadPool
  *
  * Returns the maximal number of threads for @pool.
  *
  * Return value: the maximal number of threads
  **/
 gint
 g_thread_pool_get_max_threads (GThreadPool     *pool)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;
   gint retval;

   g_return_val_if_fail (real, 0);
   g_return_val_if_fail (real->running, 0);

   g_async_queue_lock (real->queue);

   retval = real->max_threads;

   g_async_queue_unlock (real->queue);

   return retval;
 }

 /**
  * g_thread_pool_get_num_threads:
  * @pool: a #GThreadPool
  *
  * Returns the number of threads currently running in @pool.
  *
  * Return value: the number of threads currently running
  **/
 guint
 g_thread_pool_get_num_threads (GThreadPool     *pool)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;
   guint retval;

   g_return_val_if_fail (real, 0);
   g_return_val_if_fail (real->running, 0);

   g_async_queue_lock (real->queue);

   retval = real->num_threads;

   g_async_queue_unlock (real->queue);

   return retval;
 }

 /**
  * g_thread_pool_unprocessed:
  * @pool: a #GThreadPool
  *
  * Returns the number of tasks still unprocessed in @pool.
  *
  * Return value: the number of unprocessed tasks
  **/
 guint
 g_thread_pool_unprocessed (GThreadPool     *pool)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;
   gint unprocessed;

   g_return_val_if_fail (real, 0);
   g_return_val_if_fail (real->running, 0);

   unprocessed = g_async_queue_length (real->queue);

   return MAX (unprocessed, 0);
 }

 /**
  * g_thread_pool_free:
  * @pool: a #GThreadPool
  * @immediate: should @pool shut down immediately?
  * @wait: should the function wait for all tasks to be finished?
  *
  * Frees all resources allocated for @pool.
  *
  * If @immediate is %TRUE, no new task is processed for
  * @pool. Otherwise @pool is not freed before the last task is
  * processed. Note however, that no thread of this pool is
  * interrupted, while processing a task. Instead at least all still
  * running threads can finish their tasks before the @pool is freed.
  *
  * If @wait is %TRUE, the functions does not return before all tasks
  * to be processed (dependent on @immediate, whether all or only the
  * currently running) are ready. Otherwise the function returns immediately.
  *
  * After calling this function @pool must not be used anymore.
  **/
 void
 g_thread_pool_free (GThreadPool     *pool,
 		    gboolean         immediate,
 		    gboolean         wait)
 {
   GRealThreadPool *real = (GRealThreadPool*) pool;

   g_return_if_fail (real);
   g_return_if_fail (real->running);
   /* It there's no thread allowed here, there is not much sense in
    * not stopping this pool immediately, when it's not empty */
   g_return_if_fail (immediate || real->max_threads != 0 ||
 		    g_async_queue_length (real->queue) == 0);

   g_async_queue_lock (real->queue);

   real->running = FALSE;
   real->immediate = immediate;
   real->waiting = wait;

   if (wait)
     {
       g_mutex_lock (inform_mutex);
       while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
 	{
 	  g_async_queue_unlock (real->queue);
 	  g_cond_wait (inform_cond, inform_mutex);
 	  g_async_queue_lock (real->queue);
 	}
       g_mutex_unlock (inform_mutex);
     }

   if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
     {
       /* No thread is currently doing something (and nothing is left
        * to process in the queue) */
       if (real->num_threads == 0) /* No threads left, we clean up */
 	{
 	  g_async_queue_unlock (real->queue);
 	  g_thread_pool_free_internal (real);
 	  return;
 	}

       g_thread_pool_wakeup_and_stop_all (real);
     }

   real->waiting = FALSE; /* The last thread should cleanup the pool */
   g_async_queue_unlock (real->queue);
 }

 static void
 g_thread_pool_free_internal (GRealThreadPool* pool)
 {
   g_return_if_fail (pool);
   g_return_if_fail (!pool->running);
   g_return_if_fail (pool->num_threads == 0);

   g_async_queue_unref (pool->queue);

   g_free (pool);
 }

 static void
 g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
 {
   guint i;

   g_return_if_fail (pool);
   g_return_if_fail (!pool->running);
   g_return_if_fail (pool->num_threads != 0);
   g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
 		    -pool->num_threads);

   pool->immediate = TRUE;
   for (i = 0; i < pool->num_threads; i++)
     g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
 }

 /**
  * g_thread_pool_set_max_unused_threads:
  * @max_threads: maximal number of unused threads
  *
  * Sets the maximal number of unused threads to @max_threads. If
  * @max_threads is -1, no limit is imposed on the number of unused
  * threads.
  **/
 void
 g_thread_pool_set_max_unused_threads (gint max_threads)
 {
   g_return_if_fail (max_threads >= -1);

   G_LOCK (unused_threads);

   max_unused_threads = max_threads;

   if (max_unused_threads < unused_threads && max_unused_threads != -1)
     {
       guint i;

       g_async_queue_lock (unused_thread_queue);
       for (i = unused_threads - max_unused_threads; i > 0; i--)
 	g_async_queue_push_unlocked (unused_thread_queue,
 				     stop_this_thread_marker);
       g_async_queue_unlock (unused_thread_queue);
     }

   G_UNLOCK (unused_threads);
 }

 /**
  * g_thread_pool_get_max_unused_threads:
  *
  * Returns the maximal allowed number of unused threads.
  *
  * Return value: the maximal number of unused threads
  **/
 gint
 g_thread_pool_get_max_unused_threads (void)
 {
   gint retval;

   G_LOCK (unused_threads);
   retval = max_unused_threads;
   G_UNLOCK (unused_threads);

   return retval;
 }

 /**
  * g_thread_pool_get_num_unused_threads:
  *
  * Returns the number of currently unused threads.
  *
  * Return value: the number of currently unused threads
  **/
 guint g_thread_pool_get_num_unused_threads (void)
 {
   guint retval;

   G_LOCK (unused_threads);
   retval = unused_threads;
   G_UNLOCK (unused_threads);

   return retval;
 }

 /**
  * g_thread_pool_stop_unused_threads:
  *
  * Stops all currently unused threads. This does not change the
  * maximal number of unused threads. This function can be used to
  * regularly stop all unused threads e.g. from g_timeout_add().
  **/
 void g_thread_pool_stop_unused_threads (void)
 {
   guint oldval = g_thread_pool_get_max_unused_threads ();
   g_thread_pool_set_max_unused_threads (0);
   g_thread_pool_set_max_unused_threads (oldval);
 }
	/* GLIB - Library of useful routines for C programming
	* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
	*
	* GAsyncQueue: thread pool implementation.
	* Copyright (C) 2000 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 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, write to the
	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	* Boston, MA 02111-1307, USA.
	*/

	/*
	* MT safe
	*/

	#include "config.h"

	#include "galias.h"
	#include "glib.h"


	typedef struct _GRealThreadPool GRealThreadPool;

	struct _GRealThreadPool
	{
	GThreadPool pool;
	GAsyncQueue* queue;
	gint max_threads;
	gint num_threads;
	gboolean running;
	gboolean immediate;
	gboolean waiting;
	};

	/* The following is just an address to mark the stop order for a
	* thread, it could be any address (as long, as it isn't a valid
	* GThreadPool address) */
	static const gpointer stop_this_thread_marker = (gpointer) &g_thread_pool_new;

	/* Here all unused threads are waiting */
	static GAsyncQueue *unused_thread_queue;
	static gint unused_threads = 0;
	static gint max_unused_threads = 0;
	G_LOCK_DEFINE_STATIC (unused_threads);

	static GMutex *inform_mutex = NULL;
	static GCond *inform_cond = NULL;

	static void g_thread_pool_free_internal (GRealThreadPool* pool);
	static gpointer g_thread_pool_thread_proxy (gpointer data);
	static void g_thread_pool_start_thread (GRealThreadPool* pool,
	GError **error);
	static void g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool);

	#define g_thread_should_run(pool, len) \
	((pool)->running \|\| (!(pool)->immediate && (len) > 0))

	static gpointer
	g_thread_pool_thread_proxy (gpointer data)
	{
	GRealThreadPool *pool = data;
	gboolean watcher = FALSE;

	g_async_queue_lock (pool->queue);
	while (TRUE)
	{
	gpointer task;
	gboolean goto_global_pool = !pool->pool.exclusive;
	gint len = g_async_queue_length_unlocked (pool->queue);

	if (g_thread_should_run (pool, len))
	{
	if (watcher)
	{
	/* This thread is actually not needed here, but it waits
	* for some time anyway. If during that time a new
	* request arrives, this saves process
	* swicthes. Otherwise the thread will go to the global
	* pool afterwards */
	GTimeVal end_time;
	g_get_current_time (&end_time);
	g_time_val_add (&end_time, G_USEC_PER_SEC / 2); /* 1/2 second */
	task = g_async_queue_timed_pop_unlocked (pool->queue, &end_time);
	}
	else
	task = g_async_queue_pop_unlocked (pool->queue);

	if (task)
	{
	watcher = FALSE;
	if (pool->num_threads > pool->max_threads &&
	pool->max_threads != -1)
	/* We are in fact a superfluous threads, so we go to
	* the global pool and just hand the data further to
	* the next one waiting in the queue */
	{
	g_async_queue_push_unlocked (pool->queue, task);
	goto_global_pool = TRUE;
	}
	else if (pool->running \|\| !pool->immediate)
	{
	g_async_queue_unlock (pool->queue);
	pool->pool.func (task, pool->pool.user_data);
	g_async_queue_lock (pool->queue);
	}
	}
	len = g_async_queue_length_unlocked (pool->queue);
	}

	if (!g_thread_should_run (pool, len))
	{
	g_cond_broadcast (inform_cond);
	goto_global_pool = TRUE;
	}
	else if (len > 0)
	{
	/* At this pool there are no threads waiting, but tasks are. */
	goto_global_pool = FALSE;
	}
	else if (len == 0 && !watcher && !pool->pool.exclusive)
	{
	/* Here neither threads nor tasks are queued and we didn't
	* just return from a timed wait. We now wait for a limited
	* time at this pool for new tasks to avoid costly context
	* switches. */
	goto_global_pool = FALSE;
	watcher = TRUE;
	}

	if (goto_global_pool)
	{
	pool->num_threads--;

	if (!pool->running && !pool->waiting)
	{
	if (pool->num_threads == 0)
	{
	g_async_queue_unlock (pool->queue);
	g_thread_pool_free_internal (pool);
	}
	else
	{
	if (len == - pool->num_threads)
	g_thread_pool_wakeup_and_stop_all (pool);

	g_async_queue_unlock (pool->queue);
	}
	}
	else
	g_async_queue_unlock (pool->queue);

	g_async_queue_lock (unused_thread_queue);

	G_LOCK (unused_threads);
	if ((unused_threads >= max_unused_threads &&
	max_unused_threads != -1))
	{
	G_UNLOCK (unused_threads);
	g_async_queue_unlock (unused_thread_queue);
	/* Stop this thread */
	return NULL;
	}
	unused_threads++;
	G_UNLOCK (unused_threads);

	pool = g_async_queue_pop_unlocked (unused_thread_queue);

	G_LOCK (unused_threads);
	unused_threads--;
	G_UNLOCK (unused_threads);

	g_async_queue_unlock (unused_thread_queue);

	if (pool == stop_this_thread_marker)
	/* Stop this thread */
	return NULL;

	g_async_queue_lock (pool->queue);

	/* pool->num_threads++ is not done here, but in
	* g_thread_pool_start_thread to make the new started thread
	* known to the pool, before itself can do it. */
	}
	}
	return NULL;
	}

	static void
	g_thread_pool_start_thread (GRealThreadPool *pool,
	GError **error)
	{
	gboolean success = FALSE;

	if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
	/* Enough threads are already running */
	return;

	g_async_queue_lock (unused_thread_queue);

	if (g_async_queue_length_unlocked (unused_thread_queue) < 0)
	{
	g_async_queue_push_unlocked (unused_thread_queue, pool);
	success = TRUE;
	}

	g_async_queue_unlock (unused_thread_queue);

	if (!success)
	{
	GError *local_error = NULL;
	/* No thread was found, we have to start a new one */
	g_thread_create (g_thread_pool_thread_proxy, pool, FALSE, &local_error);

	if (local_error)
	{
	g_propagate_error (error, local_error);
	return;
	}
	}

	/* See comment in g_thread_pool_thread_proxy as to why this is done
	* here and not there */
	pool->num_threads++;
	}

	/**
	* g_thread_pool_new:
	* @func: a function to execute in the threads of the new thread pool
	* @user_data: user data that is handed over to @func every time it
	* is called
	* @max_threads: the maximal number of threads to execute concurrently in
	* the new thread pool, -1 means no limit
	* @exclusive: should this thread pool be exclusive?
	* @error: return location for error
	*
	* This function creates a new thread pool.
	*
	* Whenever you call g_thread_pool_push(), either a new thread is
	* created or an unused one is reused. At most @max_threads threads
	* are running concurrently for this thread pool. @max_threads = -1
	* allows unlimited threads to be created for this thread pool. The
	* newly created or reused thread now executes the function @func with
	* the two arguments. The first one is the parameter to
	* g_thread_pool_push() and the second one is @user_data.
	*
	* The parameter @exclusive determines, whether the thread pool owns
	* all threads exclusive or whether the threads are shared
	* globally. If @exclusive is %TRUE, @max_threads threads are started
	* immediately and they will run exclusively for this thread pool until
	* it is destroyed by g_thread_pool_free(). If @exclusive is %FALSE,
	* threads are created, when needed and shared between all
	* non-exclusive thread pools. This implies that @max_threads may not
	* be -1 for exclusive thread pools.
	*
	* @error can be %NULL to ignore errors, or non-%NULL to report
	* errors. An error can only occur when @exclusive is set to %TRUE and
	* not all @max_threads threads could be created.
	*
	* Return value: the new #GThreadPool
	**/
	GThreadPool*
	g_thread_pool_new (GFunc func,
	gpointer user_data,
	gint max_threads,
	gboolean exclusive,
	GError **error)
	{
	GRealThreadPool *retval;
	G_LOCK_DEFINE_STATIC (init);

	g_return_val_if_fail (func, NULL);
	g_return_val_if_fail (!exclusive \|\| max_threads != -1, NULL);
	g_return_val_if_fail (max_threads >= -1, NULL);
	g_return_val_if_fail (g_thread_supported (), NULL);

	retval = g_new (GRealThreadPool, 1);

	retval->pool.func = func;
	retval->pool.user_data = user_data;
	retval->pool.exclusive = exclusive;
	retval->queue = g_async_queue_new ();
	retval->max_threads = max_threads;
	retval->num_threads = 0;
	retval->running = TRUE;

	G_LOCK (init);

	if (!inform_mutex)
	{
	inform_mutex = g_mutex_new ();
	inform_cond = g_cond_new ();
	unused_thread_queue = g_async_queue_new ();
	}

	G_UNLOCK (init);

	if (retval->pool.exclusive)
	{
	g_async_queue_lock (retval->queue);

	while (retval->num_threads < retval->max_threads)
	{
	GError *local_error = NULL;
	g_thread_pool_start_thread (retval, &local_error);
	if (local_error)
	{
	g_propagate_error (error, local_error);
	break;
	}
	}

	g_async_queue_unlock (retval->queue);
	}

	return (GThreadPool*) retval;
	}

	/**
	* g_thread_pool_push:
	* @pool: a #GThreadPool
	* @data: a new task for @pool
	* @error: return location for error
	*
	* Inserts @data into the list of tasks to be executed by @pool. When
	* the number of currently running threads is lower than the maximal
	* allowed number of threads, a new thread is started (or reused) with
	* the properties given to g_thread_pool_new (). Otherwise @data stays
	* in the queue until a thread in this pool finishes its previous task
	* and processes @data.
	*
	* @error can be %NULL to ignore errors, or non-%NULL to report
	* errors. An error can only occur when a new thread couldn't be
	* created. In that case @data is simply appended to the queue of work
	* to do.
	**/
	void
	g_thread_pool_push (GThreadPool *pool,
	gpointer data,
	GError **error)
	{
	GRealThreadPool real = (GRealThreadPool) pool;

	g_return_if_fail (real);

	g_async_queue_lock (real->queue);

	if (!real->running)
	{
	g_async_queue_unlock (real->queue);
	g_return_if_fail (real->running);
	}

	if (g_async_queue_length_unlocked (real->queue) >= 0)
	/* No thread is waiting in the queue */
	g_thread_pool_start_thread (real, error);

	g_async_queue_push_unlocked (real->queue, data);
	g_async_queue_unlock (real->queue);
	}

	/**
	* g_thread_pool_set_max_threads:
	* @pool: a #GThreadPool
	* @max_threads: a new maximal number of threads for @pool
	* @error: return location for error
	*
	* Sets the maximal allowed number of threads for @pool. A value of -1
	* means, that the maximal number of threads is unlimited.
	*
	* Setting @max_threads to 0 means stopping all work for @pool. It is
	* effectively frozen until @max_threads is set to a non-zero value
	* again.
	*
	* A thread is never terminated while calling @func, as supplied by
	* g_thread_pool_new (). Instead the maximal number of threads only
	* has effect for the allocation of new threads in g_thread_pool_push().
	* A new thread is allocated, whenever the number of currently
	* running threads in @pool is smaller than the maximal number.
	*
	* @error can be %NULL to ignore errors, or non-%NULL to report
	* errors. An error can only occur when a new thread couldn't be
	* created.
	**/
	void
	g_thread_pool_set_max_threads (GThreadPool *pool,
	gint max_threads,
	GError **error)
	{
	GRealThreadPool real = (GRealThreadPool) pool;
	gint to_start;

	g_return_if_fail (real);
	g_return_if_fail (real->running);
	g_return_if_fail (!real->pool.exclusive \|\| max_threads != -1);
	g_return_if_fail (max_threads >= -1);

	g_async_queue_lock (real->queue);

	real->max_threads = max_threads;

	if (pool->exclusive)
	to_start = real->max_threads - real->num_threads;
	else
	to_start = g_async_queue_length_unlocked (real->queue);

	for ( ; to_start > 0; to_start--)
	{
	GError *local_error = NULL;
	g_thread_pool_start_thread (real, &local_error);
	if (local_error)
	{
	g_propagate_error (error, local_error);
	break;
	}
	}

	g_async_queue_unlock (real->queue);
	}

	/**
	* g_thread_pool_get_max_threads:
	* @pool: a #GThreadPool
	*
	* Returns the maximal number of threads for @pool.
	*
	* Return value: the maximal number of threads
	**/
	gint
	g_thread_pool_get_max_threads (GThreadPool *pool)
	{
	GRealThreadPool real = (GRealThreadPool) pool;
	gint retval;

	g_return_val_if_fail (real, 0);
	g_return_val_if_fail (real->running, 0);

	g_async_queue_lock (real->queue);

	retval = real->max_threads;

	g_async_queue_unlock (real->queue);

	return retval;
	}

	/**
	* g_thread_pool_get_num_threads:
	* @pool: a #GThreadPool
	*
	* Returns the number of threads currently running in @pool.
	*
	* Return value: the number of threads currently running
	**/
	guint
	g_thread_pool_get_num_threads (GThreadPool *pool)
	{
	GRealThreadPool real = (GRealThreadPool) pool;
	guint retval;

	g_return_val_if_fail (real, 0);
	g_return_val_if_fail (real->running, 0);

	g_async_queue_lock (real->queue);

	retval = real->num_threads;

	g_async_queue_unlock (real->queue);

	return retval;
	}

	/**
	* g_thread_pool_unprocessed:
	* @pool: a #GThreadPool
	*
	* Returns the number of tasks still unprocessed in @pool.
	*
	* Return value: the number of unprocessed tasks
	**/
	guint
	g_thread_pool_unprocessed (GThreadPool *pool)
	{
	GRealThreadPool real = (GRealThreadPool) pool;
	gint unprocessed;

	g_return_val_if_fail (real, 0);
	g_return_val_if_fail (real->running, 0);

	unprocessed = g_async_queue_length (real->queue);

	return MAX (unprocessed, 0);
	}

	/**
	* g_thread_pool_free:
	* @pool: a #GThreadPool
	* @immediate: should @pool shut down immediately?
	* @wait: should the function wait for all tasks to be finished?
	*
	* Frees all resources allocated for @pool.
	*
	* If @immediate is %TRUE, no new task is processed for
	* @pool. Otherwise @pool is not freed before the last task is
	* processed. Note however, that no thread of this pool is
	* interrupted, while processing a task. Instead at least all still
	* running threads can finish their tasks before the @pool is freed.
	*
	* If @wait is %TRUE, the functions does not return before all tasks
	* to be processed (dependent on @immediate, whether all or only the
	* currently running) are ready. Otherwise the function returns immediately.
	*
	* After calling this function @pool must not be used anymore.
	**/
	void
	g_thread_pool_free (GThreadPool *pool,
	gboolean immediate,
	gboolean wait)
	{
	GRealThreadPool real = (GRealThreadPool) pool;

	g_return_if_fail (real);
	g_return_if_fail (real->running);
	/* It there's no thread allowed here, there is not much sense in
	* not stopping this pool immediately, when it's not empty */
	g_return_if_fail (immediate \|\| real->max_threads != 0 \|\|
	g_async_queue_length (real->queue) == 0);

	g_async_queue_lock (real->queue);

	real->running = FALSE;
	real->immediate = immediate;
	real->waiting = wait;

	if (wait)
	{
	g_mutex_lock (inform_mutex);
	while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
	{
	g_async_queue_unlock (real->queue);
	g_cond_wait (inform_cond, inform_mutex);
	g_async_queue_lock (real->queue);
	}
	g_mutex_unlock (inform_mutex);
	}

	if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
	{
	/* No thread is currently doing something (and nothing is left
	* to process in the queue) */
	if (real->num_threads == 0) /* No threads left, we clean up */
	{
	g_async_queue_unlock (real->queue);
	g_thread_pool_free_internal (real);
	return;
	}

	g_thread_pool_wakeup_and_stop_all (real);
	}

	real->waiting = FALSE; /* The last thread should cleanup the pool */
	g_async_queue_unlock (real->queue);
	}

	static void
	g_thread_pool_free_internal (GRealThreadPool* pool)
	{
	g_return_if_fail (pool);
	g_return_if_fail (!pool->running);
	g_return_if_fail (pool->num_threads == 0);

	g_async_queue_unref (pool->queue);

	g_free (pool);
	}

	static void
	g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
	{
	guint i;

	g_return_if_fail (pool);
	g_return_if_fail (!pool->running);
	g_return_if_fail (pool->num_threads != 0);
	g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
	-pool->num_threads);

	pool->immediate = TRUE;
	for (i = 0; i < pool->num_threads; i++)
	g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
	}

	/**
	* g_thread_pool_set_max_unused_threads:
	* @max_threads: maximal number of unused threads
	*
	* Sets the maximal number of unused threads to @max_threads. If
	* @max_threads is -1, no limit is imposed on the number of unused
	* threads.
	**/
	void
	g_thread_pool_set_max_unused_threads (gint max_threads)
	{
	g_return_if_fail (max_threads >= -1);

	G_LOCK (unused_threads);

	max_unused_threads = max_threads;

	if (max_unused_threads < unused_threads && max_unused_threads != -1)
	{
	guint i;

	g_async_queue_lock (unused_thread_queue);
	for (i = unused_threads - max_unused_threads; i > 0; i--)
	g_async_queue_push_unlocked (unused_thread_queue,
	stop_this_thread_marker);
	g_async_queue_unlock (unused_thread_queue);
	}

	G_UNLOCK (unused_threads);
	}

	/**
	* g_thread_pool_get_max_unused_threads:
	*
	* Returns the maximal allowed number of unused threads.
	*
	* Return value: the maximal number of unused threads
	**/
	gint
	g_thread_pool_get_max_unused_threads (void)
	{
	gint retval;

	G_LOCK (unused_threads);
	retval = max_unused_threads;
	G_UNLOCK (unused_threads);

	return retval;
	}

	/**
	* g_thread_pool_get_num_unused_threads:
	*
	* Returns the number of currently unused threads.
	*
	* Return value: the number of currently unused threads
	**/
	guint g_thread_pool_get_num_unused_threads (void)
	{
	guint retval;

	G_LOCK (unused_threads);
	retval = unused_threads;
	G_UNLOCK (unused_threads);

	return retval;
	}

	/**
	* g_thread_pool_stop_unused_threads:
	*
	* Stops all currently unused threads. This does not change the
	* maximal number of unused threads. This function can be used to
	* regularly stop all unused threads e.g. from g_timeout_add().
	**/
	void g_thread_pool_stop_unused_threads (void)
	{
	guint oldval = g_thread_pool_get_max_unused_threads ();
	g_thread_pool_set_max_unused_threads (0);
	g_thread_pool_set_max_unused_threads (oldval);
	}