1/* GIO - GLib Input, Output and Streaming Library
2 *
3 * Copyright (C) 2006-2007 Red Hat, Inc.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General
16 * Public License along with this library; if not, write to the
17 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
18 * Boston, MA 02111-1307, USA.
19 *
20 * Author: Alexander Larsson <alexl@redhat.com>
21 */
22
23#include "config.h"
24
25#include "gioscheduler.h"
26#include "gcancellable.h"
27
28#include "gioalias.h"
29
30/**
31 * SECTION:gioscheduler
32 * @short_description: I/O Scheduler
33 * @include: gio/gio.h
34 *
35 * Schedules asynchronous I/O operations. #GIOScheduler integrates
36 * into the main event loop (#GMainLoop) and may use threads if they
37 * are available.
38 *
39 * <para id="io-priority"><indexterm><primary>I/O priority</primary></indexterm>
40 * Each I/O operation has a priority, and the scheduler uses the priorities
41 * to determine the order in which operations are executed. They are
42 * <emphasis>not</emphasis> used to determine system-wide I/O scheduling.
43 * Priorities are integers, with lower numbers indicating higher priority.
44 * It is recommended to choose priorities between %G_PRIORITY_LOW and
45 * %G_PRIORITY_HIGH, with %G_PRIORITY_DEFAULT as a default.
46 * </para>
47 **/
48
49struct _GIOSchedulerJob {
50  GSList *active_link;
51  GIOSchedulerJobFunc job_func;
52  GSourceFunc cancel_func; /* Runs under job map lock */
53  gpointer data;
54  GDestroyNotify destroy_notify;
55
56  gint io_priority;
57  GCancellable *cancellable;
58
59  guint idle_tag;
60};
61
62G_LOCK_DEFINE_STATIC(active_jobs);
63static GSList *active_jobs = NULL;
64
65static GThreadPool *job_thread_pool = NULL;
66
67static void io_job_thread (gpointer data,
68			   gpointer user_data);
69
70static void
71g_io_job_free (GIOSchedulerJob *job)
72{
73  if (job->cancellable)
74    g_object_unref (job->cancellable);
75  g_free (job);
76}
77
78static gint
79g_io_job_compare (gconstpointer a,
80		  gconstpointer b,
81		  gpointer      user_data)
82{
83  const GIOSchedulerJob *aa = a;
84  const GIOSchedulerJob *bb = b;
85
86  /* Cancelled jobs are set prio == -1, so that
87     they are executed as quickly as possible */
88
89  /* Lower value => higher priority */
90  if (aa->io_priority < bb->io_priority)
91    return -1;
92  if (aa->io_priority == bb->io_priority)
93    return 0;
94  return 1;
95}
96
97static gpointer
98init_scheduler (gpointer arg)
99{
100  if (job_thread_pool == NULL)
101    {
102      /* TODO: thread_pool_new can fail */
103      job_thread_pool = g_thread_pool_new (io_job_thread,
104					   NULL,
105					   10,
106					   FALSE,
107					   NULL);
108      if (job_thread_pool != NULL)
109	{
110	  g_thread_pool_set_sort_function (job_thread_pool,
111					   g_io_job_compare,
112					   NULL);
113	  /* It's kinda weird that this is a global setting
114	   * instead of per threadpool. However, we really
115	   * want to cache some threads, but not keep around
116	   * those threads forever. */
117	  g_thread_pool_set_max_idle_time (15 * 1000);
118	  g_thread_pool_set_max_unused_threads (2);
119	}
120    }
121  return NULL;
122}
123
124static void
125remove_active_job (GIOSchedulerJob *job)
126{
127  GIOSchedulerJob *other_job;
128  GSList *l;
129  gboolean resort_jobs;
130
131  G_LOCK (active_jobs);
132  active_jobs = g_slist_delete_link (active_jobs, job->active_link);
133
134  resort_jobs = FALSE;
135  for (l = active_jobs; l != NULL; l = l->next)
136    {
137      other_job = l->data;
138      if (other_job->io_priority >= 0 &&
139	  g_cancellable_is_cancelled (other_job->cancellable))
140	{
141	  other_job->io_priority = -1;
142	  resort_jobs = TRUE;
143	}
144    }
145  G_UNLOCK (active_jobs);
146
147  if (resort_jobs &&
148      job_thread_pool != NULL)
149    g_thread_pool_set_sort_function (job_thread_pool,
150				     g_io_job_compare,
151				     NULL);
152
153}
154
155static void
156job_destroy (gpointer data)
157{
158  GIOSchedulerJob *job = data;
159
160  if (job->destroy_notify)
161    job->destroy_notify (job->data);
162
163  remove_active_job (job);
164  g_io_job_free (job);
165}
166
167static void
168io_job_thread (gpointer data,
169	       gpointer user_data)
170{
171  GIOSchedulerJob *job = data;
172  gboolean result;
173
174  if (job->cancellable)
175    g_cancellable_push_current (job->cancellable);
176
177  do
178    {
179      result = job->job_func (job, job->cancellable, job->data);
180    }
181  while (result);
182
183  if (job->cancellable)
184    g_cancellable_pop_current (job->cancellable);
185
186  job_destroy (job);
187}
188
189static gboolean
190run_job_at_idle (gpointer data)
191{
192  GIOSchedulerJob *job = data;
193  gboolean result;
194
195  if (job->cancellable)
196    g_cancellable_push_current (job->cancellable);
197
198  result = job->job_func (job, job->cancellable, job->data);
199
200  if (job->cancellable)
201    g_cancellable_pop_current (job->cancellable);
202
203  return result;
204}
205
206/**
207 * g_io_scheduler_push_job:
208 * @job_func: a #GIOSchedulerJobFunc.
209 * @user_data: data to pass to @job_func
210 * @notify: a #GDestroyNotify for @user_data, or %NULL
211 * @io_priority: the <link linkend="gioscheduler">I/O priority</link>
212 * of the request.
213 * @cancellable: optional #GCancellable object, %NULL to ignore.
214 *
215 * Schedules the I/O job to run.
216 *
217 * @notify will be called on @user_data after @job_func has returned,
218 * regardless whether the job was cancelled or has run to completion.
219 *
220 * If @cancellable is not %NULL, it can be used to cancel the I/O job
221 * by calling g_cancellable_cancel() or by calling
222 * g_io_scheduler_cancel_all_jobs().
223 **/
224void
225g_io_scheduler_push_job (GIOSchedulerJobFunc  job_func,
226			 gpointer             user_data,
227			 GDestroyNotify       notify,
228			 gint                 io_priority,
229			 GCancellable        *cancellable)
230{
231  static GOnce once_init = G_ONCE_INIT;
232  GIOSchedulerJob *job;
233
234  g_return_if_fail (job_func != NULL);
235
236  job = g_new0 (GIOSchedulerJob, 1);
237  job->job_func = job_func;
238  job->data = user_data;
239  job->destroy_notify = notify;
240  job->io_priority = io_priority;
241
242  if (cancellable)
243    job->cancellable = g_object_ref (cancellable);
244
245  G_LOCK (active_jobs);
246  active_jobs = g_slist_prepend (active_jobs, job);
247  job->active_link = active_jobs;
248  G_UNLOCK (active_jobs);
249
250  if (g_thread_supported())
251    {
252      g_once (&once_init, init_scheduler, NULL);
253      g_thread_pool_push (job_thread_pool, job, NULL);
254    }
255  else
256    {
257      /* Threads not available, instead do the i/o sync inside a
258       * low prio idle handler
259       */
260      job->idle_tag = g_idle_add_full (G_PRIORITY_DEFAULT_IDLE + 1 + io_priority / 10,
261				       run_job_at_idle,
262				       job, job_destroy);
263    }
264}
265
266/**
267 * g_io_scheduler_cancel_all_jobs:
268 *
269 * Cancels all cancellable I/O jobs.
270 *
271 * A job is cancellable if a #GCancellable was passed into
272 * g_io_scheduler_push_job().
273 **/
274void
275g_io_scheduler_cancel_all_jobs (void)
276{
277  GSList *cancellable_list, *l;
278
279  G_LOCK (active_jobs);
280  cancellable_list = NULL;
281  for (l = active_jobs; l != NULL; l = l->next)
282    {
283      GIOSchedulerJob *job = l->data;
284      if (job->cancellable)
285	cancellable_list = g_slist_prepend (cancellable_list,
286					    g_object_ref (job->cancellable));
287    }
288  G_UNLOCK (active_jobs);
289
290  for (l = cancellable_list; l != NULL; l = l->next)
291    {
292      GCancellable *c = l->data;
293      g_cancellable_cancel (c);
294      g_object_unref (c);
295    }
296  g_slist_free (cancellable_list);
297}
298
299typedef struct {
300  GSourceFunc func;
301  gboolean ret_val;
302  gpointer data;
303  GDestroyNotify notify;
304
305  GMutex *ack_lock;
306  GCond *ack_condition;
307} MainLoopProxy;
308
309static gboolean
310mainloop_proxy_func (gpointer data)
311{
312  MainLoopProxy *proxy = data;
313
314  proxy->ret_val = proxy->func (proxy->data);
315
316  if (proxy->notify)
317    proxy->notify (proxy->data);
318
319  if (proxy->ack_lock)
320    {
321      g_mutex_lock (proxy->ack_lock);
322      g_cond_signal (proxy->ack_condition);
323      g_mutex_unlock (proxy->ack_lock);
324    }
325
326  return FALSE;
327}
328
329static void
330mainloop_proxy_free (MainLoopProxy *proxy)
331{
332  if (proxy->ack_lock)
333    {
334      g_mutex_free (proxy->ack_lock);
335      g_cond_free (proxy->ack_condition);
336    }
337
338  g_free (proxy);
339}
340
341/**
342 * g_io_scheduler_job_send_to_mainloop:
343 * @job: a #GIOSchedulerJob
344 * @func: a #GSourceFunc callback that will be called in the main thread
345 * @user_data: data to pass to @func
346 * @notify: a #GDestroyNotify for @user_data, or %NULL
347 *
348 * Used from an I/O job to send a callback to be run in the
349 * main loop (main thread), waiting for the result (and thus
350 * blocking the I/O job).
351 *
352 * Returns: The return value of @func
353 **/
354gboolean
355g_io_scheduler_job_send_to_mainloop (GIOSchedulerJob *job,
356				     GSourceFunc      func,
357				     gpointer         user_data,
358				     GDestroyNotify   notify)
359{
360  GSource *source;
361  MainLoopProxy *proxy;
362  guint id;
363  gboolean ret_val;
364
365  g_return_val_if_fail (job != NULL, FALSE);
366  g_return_val_if_fail (func != NULL, FALSE);
367
368  if (job->idle_tag)
369    {
370      /* We just immediately re-enter in the case of idles (non-threads)
371       * Anything else would just deadlock. If you can't handle this, enable threads.
372       */
373      ret_val = func (user_data);
374      if (notify)
375	notify (user_data);
376      return ret_val;
377    }
378
379  proxy = g_new0 (MainLoopProxy, 1);
380  proxy->func = func;
381  proxy->data = user_data;
382  proxy->notify = notify;
383  proxy->ack_lock = g_mutex_new ();
384  proxy->ack_condition = g_cond_new ();
385  g_mutex_lock (proxy->ack_lock);
386
387  source = g_idle_source_new ();
388  g_source_set_priority (source, G_PRIORITY_DEFAULT);
389  g_source_set_callback (source, mainloop_proxy_func, proxy,
390			 NULL);
391
392  id = g_source_attach (source, NULL);
393  g_source_unref (source);
394
395  g_cond_wait (proxy->ack_condition, proxy->ack_lock);
396  g_mutex_unlock (proxy->ack_lock);
397
398  ret_val = proxy->ret_val;
399  mainloop_proxy_free (proxy);
400
401  return ret_val;
402}
403
404/**
405 * g_io_scheduler_job_send_to_mainloop_async:
406 * @job: a #GIOSchedulerJob
407 * @func: a #GSourceFunc callback that will be called in the main thread
408 * @user_data: data to pass to @func
409 * @notify: a #GDestroyNotify for @user_data, or %NULL
410 *
411 * Used from an I/O job to send a callback to be run asynchronously
412 * in the main loop (main thread). The callback will be run when the
413 * main loop is available, but at that time the I/O job might have
414 * finished. The return value from the callback is ignored.
415 *
416 * Note that if you are passing the @user_data from g_io_scheduler_push_job()
417 * on to this function you have to ensure that it is not freed before
418 * @func is called, either by passing %NULL as @notify to
419 * g_io_scheduler_push_job() or by using refcounting for @user_data.
420 **/
421void
422g_io_scheduler_job_send_to_mainloop_async (GIOSchedulerJob *job,
423					   GSourceFunc      func,
424					   gpointer         user_data,
425					   GDestroyNotify   notify)
426{
427  GSource *source;
428  MainLoopProxy *proxy;
429  guint id;
430
431  g_return_if_fail (job != NULL);
432  g_return_if_fail (func != NULL);
433
434  if (job->idle_tag)
435    {
436      /* We just immediately re-enter in the case of idles (non-threads)
437       * Anything else would just deadlock. If you can't handle this, enable threads.
438       */
439      func (user_data);
440      if (notify)
441	notify (user_data);
442      return;
443    }
444
445  proxy = g_new0 (MainLoopProxy, 1);
446  proxy->func = func;
447  proxy->data = user_data;
448  proxy->notify = notify;
449
450  source = g_idle_source_new ();
451  g_source_set_priority (source, G_PRIORITY_DEFAULT);
452  g_source_set_callback (source, mainloop_proxy_func, proxy,
453			 (GDestroyNotify)mainloop_proxy_free);
454
455  id = g_source_attach (source, NULL);
456  g_source_unref (source);
457}
458
459
460#define __G_IO_SCHEDULER_C__
461#include "gioaliasdef.c"
462