glib/gthreadpool.c

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/* 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 Library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library 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 "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 = &g_thread_pool_new;
/* Here all unused threads are waiting, depending on their priority */
static GAsyncQueue *unused_thread_queue[G_THREAD_PRIORITY_URGENT + 1];
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 void g_thread_pool_thread_proxy (gpointer data);
static void g_thread_pool_start_thread (GRealThreadPool* pool);
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 void
g_thread_pool_thread_proxy (gpointer data)
{
GRealThreadPool *pool = data;
GThread* self = g_thread_self ();
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))
{
task = g_async_queue_pop_unlocked (pool->queue);
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.thread_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);
if (!pool->running && (pool->immediate || len <= 0))
goto_global_pool = TRUE;
else if (len >= 0)
/* At this pool there is no thread waiting */
goto_global_pool = FALSE;
if (goto_global_pool)
{
GThreadPriority priority = pool->pool.priority;
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);
}
else
g_async_queue_unlock (pool->queue);
g_async_queue_lock (unused_thread_queue[priority]);
G_LOCK (unused_threads);
if (unused_threads >= max_unused_threads)
{
G_UNLOCK (unused_threads);
g_async_queue_unlock (unused_thread_queue[priority]);
/* Stop this thread */
return;
}
unused_threads++;
G_UNLOCK (unused_threads);
pool =
g_async_queue_pop_unlocked (unused_thread_queue[priority]);
G_LOCK (unused_threads);
unused_threads--;
G_UNLOCK (unused_threads);
g_async_queue_unlock (unused_thread_queue[priority]);
if (pool == stop_this_thread_marker)
/* Stop this thread */
return;
g_async_queue_lock (pool->queue);
if (pool->pool.priority != self->priority)
g_thread_set_priority (self, pool->pool.priority);
/* 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. */
}
}
}
static void
g_thread_pool_start_thread (GRealThreadPool* pool)
{
gboolean success = FALSE;
GThreadPriority priority = pool->pool.priority;
GAsyncQueue *queue = unused_thread_queue[priority];
if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
/* Enough threads are already running */
return;
g_async_queue_lock (queue);
if (g_async_queue_length_unlocked (queue) < 0)
{
/* First we try a thread with the right priority */
g_async_queue_push_unlocked (queue, pool);
success = TRUE;
}
g_async_queue_unlock (queue);
if (!success)
{
/* Now we search for threads with other priorities too, but
* only, when there is more than one unused thread with that
* priority. */
GThreadPriority priority;
for (priority = G_THREAD_PRIORITY_LOW;
priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
{
queue = unused_thread_queue[priority];
g_async_queue_lock (queue);
if (g_async_queue_length_unlocked (queue) < -1)
{
g_async_queue_push_unlocked (queue, pool);
success = TRUE;
}
g_async_queue_unlock (queue);
}
}
if (!success)
/* No thread was found, we have to start one new */
g_thread_create (g_thread_pool_thread_proxy, pool, pool->pool.stack_size,
FALSE, pool->pool.bound, priority);
/* See comment in g_thread_pool_thread_proxy as to why this is done
* here and not there */
pool->num_threads++;
}
GThreadPool*
g_thread_pool_new (GFunc thread_func,
gint max_threads,
gulong stack_size,
gboolean bound,
GThreadPriority priority,
gboolean exclusive,
gpointer user_data)
{
GRealThreadPool *retval;
g_return_val_if_fail (thread_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.thread_func = thread_func;
retval->pool.stack_size = stack_size;
retval->pool.bound = bound;
retval->pool.priority = priority;
retval->pool.exclusive = exclusive;
retval->pool.user_data = user_data;
retval->queue = g_async_queue_new ();
retval->max_threads = max_threads;
retval->num_threads = 0;
retval->running = TRUE;
if (!inform_mutex)
{
inform_mutex = g_mutex_new ();
inform_cond = g_cond_new ();
for (priority = G_THREAD_PRIORITY_LOW;
priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
unused_thread_queue[priority] = g_async_queue_new ();
}
if (retval->pool.exclusive)
{
g_async_queue_lock (retval->queue);
while (retval->num_threads < retval->max_threads)
g_thread_pool_start_thread (retval);
g_async_queue_unlock (retval->queue);
}
return (GThreadPool*) retval;
}
void
g_thread_pool_push (GThreadPool *pool,
gpointer data)
{
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 (!pool->exclusive && g_async_queue_length_unlocked (real->queue) >= 0)
{
/* No thread is waiting in the queue */
g_thread_pool_start_thread (real);
}
g_async_queue_push_unlocked (real->queue, data);
g_async_queue_unlock (real->queue);
}
void
g_thread_pool_set_max_threads (GThreadPool *pool,
gint max_threads)
{
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--)
g_thread_pool_start_thread (real);
g_async_queue_unlock (real->queue);
}
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;
}
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;
}
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);
}
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 immediatly, 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));
}
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 close_down_num = unused_threads - max_unused_threads;
GThreadPriority priority;
while (close_down_num > 0)
{
guint old_close_down_num = close_down_num;
for (priority = G_THREAD_PRIORITY_LOW;
priority < G_THREAD_PRIORITY_URGENT + 1 && close_down_num > 0;
priority++)
{
GAsyncQueue *queue = unused_thread_queue[priority];
g_async_queue_lock (queue);
if (g_async_queue_length_unlocked (queue) < 0)
{
g_async_queue_push_unlocked (queue,
stop_this_thread_marker);
close_down_num--;
}
g_async_queue_unlock (queue);
}
/* Just to make sure, there are no counting problems */
g_assert (old_close_down_num != close_down_num);
}
}
G_UNLOCK (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;
}
guint g_thread_pool_get_num_unused_threads (void)
{
guint retval;
G_LOCK (unused_threads);
retval = unused_threads;
G_UNLOCK (unused_threads);
return retval;
}
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);
}