1 /* GIO - GLib Input, Output and Streaming Library
3 * Copyright (C) 2006-2007 Red Hat, Inc.
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.
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.
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.
20 * Author: Alexander Larsson <alexl@redhat.com>
34 #include "gcancellable.h"
35 #include "gio-marshal.h"
40 * SECTION:gcancellable
41 * @short_description: Thread-safe Operation Cancellation Stack
44 * GCancellable is a thread-safe operation cancellation stack used
45 * throughout GIO to allow for cancellation of synchronous and
46 * asynchronous operations.
54 struct _GCancellablePrivate
57 guint cancelled_running
: 1;
58 guint cancelled_running_waiting
: 1;
68 static guint signals
[LAST_SIGNAL
] = { 0 };
70 G_DEFINE_TYPE (GCancellable
, g_cancellable
, G_TYPE_OBJECT
);
72 static GStaticPrivate current_cancellable
= G_STATIC_PRIVATE_INIT
;
73 G_LOCK_DEFINE_STATIC(cancellable
);
74 static GCond
*cancellable_cond
= NULL
;
77 g_cancellable_close_pipe (GCancellable
*cancellable
)
79 GCancellablePrivate
*priv
;
81 priv
= cancellable
->priv
;
83 if (priv
->cancel_pipe
[0] != -1)
85 close (priv
->cancel_pipe
[0]);
86 priv
->cancel_pipe
[0] = -1;
89 if (priv
->cancel_pipe
[1] != -1)
91 close (priv
->cancel_pipe
[1]);
92 priv
->cancel_pipe
[1] = -1;
98 CloseHandle (priv
->event
);
105 g_cancellable_finalize (GObject
*object
)
107 GCancellable
*cancellable
= G_CANCELLABLE (object
);
109 g_cancellable_close_pipe (cancellable
);
111 G_OBJECT_CLASS (g_cancellable_parent_class
)->finalize (object
);
115 g_cancellable_class_init (GCancellableClass
*klass
)
117 GObjectClass
*gobject_class
= G_OBJECT_CLASS (klass
);
119 g_type_class_add_private (klass
, sizeof (GCancellablePrivate
));
121 if (cancellable_cond
== NULL
&& g_thread_supported ())
122 cancellable_cond
= g_cond_new ();
124 gobject_class
->finalize
= g_cancellable_finalize
;
127 * GCancellable::cancelled:
128 * @cancellable: a #GCancellable.
130 * Emitted when the operation has been cancelled.
132 * Can be used by implementations of cancellable operations. If the
133 * operation is cancelled from another thread, the signal will be
134 * emitted in the thread that cancelled the operation, not the
135 * thread that is running the operation.
137 * Note that disconnecting from this signal (or any signal) in a
138 * multi-threaded program is prone to race conditions. For instance
139 * it is possible that a signal handler may be invoked even
140 * <emphasis>after</emphasis> a call to
141 * g_signal_handler_disconnect() for that handler has already
144 * There is also a problem when cancellation happen
145 * right before connecting to the signal. If this happens the
146 * signal will unexpectedly not be emitted, and checking before
147 * connecting to the signal leaves a race condition where this is
150 * In order to make it safe and easy to connect handlers there
151 * are two helper functions: g_cancellable_connect() and
152 * g_cancellable_disconnect() which protect against problems
155 * An example of how to us this:
157 * /<!-- -->* Make sure we don't do any unnecessary work if already cancelled *<!-- -->/
158 * if (g_cancellable_set_error_if_cancelled (cancellable))
161 * /<!-- -->* Set up all the data needed to be able to
162 * * handle cancellation of the operation *<!-- -->/
163 * my_data = my_data_new (...);
167 * id = g_cancellable_connect (cancellable,
168 * G_CALLBACK (cancelled_handler)
171 * /<!-- -->* cancellable operation here... *<!-- -->/
173 * g_cancellable_disconnect (cancellable, id);
175 * /<!-- -->* cancelled_handler is never called after this, it
176 * * is now safe to free the data *<!-- -->/
177 * my_data_free (my_data);
180 * Note that the cancelled signal is emitted in the thread that
181 * the user cancelled from, which may be the main thread. So, the
182 * cancellable signal should not do something that can block.
185 g_signal_new (I_("cancelled"),
186 G_TYPE_FROM_CLASS (gobject_class
),
188 G_STRUCT_OFFSET (GCancellableClass
, cancelled
),
190 g_cclosure_marshal_VOID__VOID
,
197 set_fd_nonblocking (int fd
)
201 fcntl_flags
= fcntl (fd
, F_GETFL
);
204 fcntl_flags
|= O_NONBLOCK
;
206 fcntl_flags
|= O_NDELAY
;
209 fcntl (fd
, F_SETFL
, fcntl_flags
);
214 set_fd_close_exec (int fd
)
218 flags
= fcntl (fd
, F_GETFD
, 0);
219 if (flags
!= -1 && (flags
& FD_CLOEXEC
) == 0)
222 fcntl (fd
, F_SETFD
, flags
);
228 g_cancellable_open_pipe (GCancellable
*cancellable
)
230 GCancellablePrivate
*priv
;
232 priv
= cancellable
->priv
;
233 if (pipe (priv
->cancel_pipe
) == 0)
235 /* Make them nonblocking, just to be sure we don't block
236 * on errors and stuff
238 set_fd_nonblocking (priv
->cancel_pipe
[0]);
239 set_fd_nonblocking (priv
->cancel_pipe
[1]);
240 set_fd_close_exec (priv
->cancel_pipe
[0]);
241 set_fd_close_exec (priv
->cancel_pipe
[1]);
249 c
= write (priv
->cancel_pipe
[1], &ch
, 1);
250 while (c
== -1 && errno
== EINTR
);
257 g_cancellable_init (GCancellable
*cancellable
)
259 cancellable
->priv
= G_TYPE_INSTANCE_GET_PRIVATE (cancellable
,
261 GCancellablePrivate
);
262 cancellable
->priv
->cancel_pipe
[0] = -1;
263 cancellable
->priv
->cancel_pipe
[1] = -1;
269 * Creates a new #GCancellable object.
271 * Applications that want to start one or more operations
272 * that should be cancellable should create a #GCancellable
273 * and pass it to the operations.
275 * One #GCancellable can be used in multiple consecutive
276 * operations, but not in multiple concurrent operations.
278 * Returns: a #GCancellable.
281 g_cancellable_new (void)
283 return g_object_new (G_TYPE_CANCELLABLE
, NULL
);
287 * g_cancellable_push_current:
288 * @cancellable: a #GCancellable object
290 * Pushes @cancellable onto the cancellable stack. The current
291 * cancellable can then be recieved using g_cancellable_get_current().
293 * This is useful when implementing cancellable operations in
294 * code that does not allow you to pass down the cancellable object.
296 * This is typically called automatically by e.g. #GFile operations,
297 * so you rarely have to call this yourself.
300 g_cancellable_push_current (GCancellable
*cancellable
)
304 g_return_if_fail (cancellable
!= NULL
);
306 l
= g_static_private_get (¤t_cancellable
);
307 l
= g_slist_prepend (l
, cancellable
);
308 g_static_private_set (¤t_cancellable
, l
, NULL
);
312 * g_cancellable_pop_current:
313 * @cancellable: a #GCancellable object
315 * Pops @cancellable off the cancellable stack (verifying that @cancellable
316 * is on the top of the stack).
319 g_cancellable_pop_current (GCancellable
*cancellable
)
323 l
= g_static_private_get (¤t_cancellable
);
325 g_return_if_fail (l
!= NULL
);
326 g_return_if_fail (l
->data
== cancellable
);
328 l
= g_slist_delete_link (l
, l
);
329 g_static_private_set (¤t_cancellable
, l
, NULL
);
333 * g_cancellable_get_current:
335 * Gets the top cancellable from the stack.
337 * Returns: (transfer none): a #GCancellable from the top of the stack, or %NULL
338 * if the stack is empty.
341 g_cancellable_get_current (void)
345 l
= g_static_private_get (¤t_cancellable
);
349 return G_CANCELLABLE (l
->data
);
353 * g_cancellable_reset:
354 * @cancellable: a #GCancellable object.
356 * Resets @cancellable to its uncancelled state.
359 g_cancellable_reset (GCancellable
*cancellable
)
361 GCancellablePrivate
*priv
;
363 g_return_if_fail (G_IS_CANCELLABLE (cancellable
));
367 priv
= cancellable
->priv
;
369 while (priv
->cancelled_running
)
371 priv
->cancelled_running_waiting
= TRUE
;
372 g_cond_wait (cancellable_cond
,
373 g_static_mutex_get_mutex (& G_LOCK_NAME (cancellable
)));
378 /* Make sure we're not leaving old cancel state around */
382 ResetEvent (priv
->event
);
384 if (priv
->cancel_pipe
[0] != -1)
390 c
= read (priv
->cancel_pipe
[0], &ch
, 1);
391 while (c
== -1 && errno
== EINTR
);
394 priv
->cancelled
= FALSE
;
396 G_UNLOCK(cancellable
);
400 * g_cancellable_is_cancelled:
401 * @cancellable: a #GCancellable or NULL.
403 * Checks if a cancellable job has been cancelled.
405 * Returns: %TRUE if @cancellable is cancelled,
406 * FALSE if called with %NULL or if item is not cancelled.
409 g_cancellable_is_cancelled (GCancellable
*cancellable
)
411 return cancellable
!= NULL
&& cancellable
->priv
->cancelled
;
415 * g_cancellable_set_error_if_cancelled:
416 * @cancellable: a #GCancellable object.
417 * @error: #GError to append error state to.
419 * If the @cancellable is cancelled, sets the error to notify
420 * that the operation was cancelled.
422 * Returns: %TRUE if @cancellable was cancelled, %FALSE if it was not.
425 g_cancellable_set_error_if_cancelled (GCancellable
*cancellable
,
428 if (g_cancellable_is_cancelled (cancellable
))
430 g_set_error_literal (error
,
432 G_IO_ERROR_CANCELLED
,
433 _("Operation was cancelled"));
441 * g_cancellable_get_fd:
442 * @cancellable: a #GCancellable.
444 * Gets the file descriptor for a cancellable job. This can be used to
445 * implement cancellable operations on Unix systems. The returned fd will
446 * turn readable when @cancellable is cancelled.
448 * You are not supposed to read from the fd yourself, just check for
449 * readable status. Reading to unset the readable status is done
450 * with g_cancellable_reset().
452 * After a successful return from this function, you should use
453 * g_cancellable_release_fd() to free up resources allocated for
454 * the returned file descriptor.
456 * See also g_cancellable_make_pollfd().
458 * Returns: A valid file descriptor. %-1 if the file descriptor
459 * is not supported, or on errors.
462 g_cancellable_get_fd (GCancellable
*cancellable
)
464 GCancellablePrivate
*priv
;
467 if (cancellable
== NULL
)
470 priv
= cancellable
->priv
;
476 if (priv
->cancel_pipe
[0] == -1)
477 g_cancellable_open_pipe (cancellable
);
478 fd
= priv
->cancel_pipe
[0];
481 G_UNLOCK(cancellable
);
488 * g_cancellable_make_pollfd:
489 * @cancellable: a #GCancellable or %NULL
490 * @pollfd: a pointer to a #GPollFD
492 * Creates a #GPollFD corresponding to @cancellable; this can be passed
493 * to g_poll() and used to poll for cancellation. This is useful both
494 * for unix systems without a native poll and for portability to
497 * When this function returns %TRUE, you should use
498 * g_cancellable_release_fd() to free up resources allocated for the
499 * @pollfd. After a %FALSE return, do not call g_cancellable_release_fd().
501 * If this function returns %FALSE, either no @cancellable was given or
502 * resource limits prevent this function from allocating the necessary
503 * structures for polling. (On Linux, you will likely have reached
504 * the maximum number of file descriptors.) The suggested way to handle
505 * these cases is to ignore the @cancellable.
507 * You are not supposed to read from the fd yourself, just check for
508 * readable status. Reading to unset the readable status is done
509 * with g_cancellable_reset().
511 * Returns: %TRUE if @pollfd was successfully initialized, %FALSE on
512 * failure to prepare the cancellable.
517 g_cancellable_make_pollfd (GCancellable
*cancellable
, GPollFD
*pollfd
)
519 g_return_val_if_fail (pollfd
!= NULL
, FALSE
);
520 if (cancellable
== NULL
)
522 g_return_val_if_fail (G_IS_CANCELLABLE (cancellable
), FALSE
);
526 GCancellablePrivate
*priv
;
528 priv
= cancellable
->priv
;
530 if (priv
->event
== NULL
)
532 /* A manual reset anonymous event, starting unset */
533 priv
->event
= CreateEvent (NULL
, TRUE
, FALSE
, NULL
);
534 if (priv
->event
== NULL
)
536 G_UNLOCK(cancellable
);
540 SetEvent(priv
->event
);
543 G_UNLOCK(cancellable
);
545 pollfd
->fd
= (gintptr
)priv
->event
;
546 #else /* !G_OS_WIN32 */
547 int fd
= g_cancellable_get_fd (cancellable
);
552 #endif /* G_OS_WIN32 */
555 pollfd
->events
= G_IO_IN
;
562 * g_cancellable_release_fd:
563 * @cancellable: a #GCancellable
565 * Releases a resources previously allocated by g_cancellable_get_fd()
566 * or g_cancellable_make_pollfd().
568 * For compatibility reasons with older releases, calling this function
569 * is not strictly required, the resources will be automatically freed
570 * when the @cancellable is finalized. However, the @cancellable will
571 * block scarce file descriptors until it is finalized if this function
572 * is not called. This can cause the application to run out of file
573 * descriptors when many #GCancellables are used at the same time.
578 g_cancellable_release_fd (GCancellable
*cancellable
)
580 GCancellablePrivate
*priv
;
582 if (cancellable
== NULL
)
585 g_return_if_fail (G_IS_CANCELLABLE (cancellable
));
586 g_return_if_fail (cancellable
->priv
->fd_refcount
> 0);
588 priv
= cancellable
->priv
;
590 G_LOCK (cancellable
);
592 if (priv
->fd_refcount
== 0)
593 g_cancellable_close_pipe (cancellable
);
594 G_UNLOCK (cancellable
);
598 * g_cancellable_cancel:
599 * @cancellable: a #GCancellable object.
601 * Will set @cancellable to cancelled, and will emit the
602 * #GCancellable::cancelled signal. (However, see the warning about
603 * race conditions in the documentation for that signal if you are
604 * planning to connect to it.)
606 * This function is thread-safe. In other words, you can safely call
607 * it from a thread other than the one running the operation that was
608 * passed the @cancellable.
610 * The convention within gio is that cancelling an asynchronous
611 * operation causes it to complete asynchronously. That is, if you
612 * cancel the operation from the same thread in which it is running,
613 * then the operation's #GAsyncReadyCallback will not be invoked until
614 * the application returns to the main loop.
617 g_cancellable_cancel (GCancellable
*cancellable
)
619 GCancellablePrivate
*priv
;
621 if (cancellable
== NULL
||
622 cancellable
->priv
->cancelled
)
625 priv
= cancellable
->priv
;
630 G_UNLOCK (cancellable
);
634 priv
->cancelled
= TRUE
;
635 priv
->cancelled_running
= TRUE
;
638 SetEvent (priv
->event
);
640 if (priv
->cancel_pipe
[1] != -1)
646 c
= write (priv
->cancel_pipe
[1], &ch
, 1);
647 while (c
== -1 && errno
== EINTR
);
649 G_UNLOCK(cancellable
);
651 g_object_ref (cancellable
);
652 g_signal_emit (cancellable
, signals
[CANCELLED
], 0);
656 priv
->cancelled_running
= FALSE
;
657 if (priv
->cancelled_running_waiting
)
658 g_cond_broadcast (cancellable_cond
);
659 priv
->cancelled_running_waiting
= FALSE
;
661 G_UNLOCK(cancellable
);
663 g_object_unref (cancellable
);
667 * g_cancellable_connect:
668 * @cancellable: A #GCancellable.
669 * @callback: The #GCallback to connect.
670 * @data: Data to pass to @callback.
671 * @data_destroy_func: Free function for @data or %NULL.
673 * Convenience function to connect to the #GCancellable::cancelled
674 * signal. Also handles the race condition that may happen
675 * if the cancellable is cancelled right before connecting.
677 * @callback is called at most once, either directly at the
678 * time of the connect if @cancellable is already cancelled,
679 * or when @cancellable is cancelled in some thread.
681 * @data_destroy_func will be called when the handler is
682 * disconnected, or immediately if the cancellable is already
685 * See #GCancellable::cancelled for details on how to use this.
687 * Returns: The id of the signal handler or 0 if @cancellable has already
693 g_cancellable_connect (GCancellable
*cancellable
,
696 GDestroyNotify data_destroy_func
)
700 g_return_val_if_fail (G_IS_CANCELLABLE (cancellable
), 0);
702 G_LOCK (cancellable
);
704 if (cancellable
->priv
->cancelled
)
706 void (*_callback
) (GCancellable
*cancellable
,
709 _callback
= (void *)callback
;
712 _callback (cancellable
, data
);
714 if (data_destroy_func
)
715 data_destroy_func (data
);
719 id
= g_signal_connect_data (cancellable
, "cancelled",
721 (GClosureNotify
) data_destroy_func
,
724 G_UNLOCK (cancellable
);
730 * g_cancellable_disconnect:
731 * @cancellable: A #GCancellable or %NULL.
732 * @handler_id: Handler id of the handler to be disconnected, or %0.
734 * Disconnects a handler from a cancellable instance similar to
735 * g_signal_handler_disconnect(). Additionally, in the event that a
736 * signal handler is currently running, this call will block until the
737 * handler has finished. Calling this function from a
738 * #GCancellable::cancelled signal handler will therefore result in a
741 * This avoids a race condition where a thread cancels at the
742 * same time as the cancellable operation is finished and the
743 * signal handler is removed. See #GCancellable::cancelled for
744 * details on how to use this.
746 * If @cancellable is %NULL or @handler_id is %0 this function does
752 g_cancellable_disconnect (GCancellable
*cancellable
,
755 GCancellablePrivate
*priv
;
757 if (handler_id
== 0 || cancellable
== NULL
)
760 G_LOCK (cancellable
);
762 priv
= cancellable
->priv
;
764 while (priv
->cancelled_running
)
766 priv
->cancelled_running_waiting
= TRUE
;
767 g_cond_wait (cancellable_cond
,
768 g_static_mutex_get_mutex (& G_LOCK_NAME (cancellable
)));
771 g_signal_handler_disconnect (cancellable
, handler_id
);
772 G_UNLOCK (cancellable
);
778 GCancellable
*cancellable
;
780 } GCancellableSource
;
783 cancellable_source_prepare (GSource
*source
,
786 GCancellableSource
*cancellable_source
= (GCancellableSource
*)source
;
789 return g_cancellable_is_cancelled (cancellable_source
->cancellable
);
793 cancellable_source_check (GSource
*source
)
795 GCancellableSource
*cancellable_source
= (GCancellableSource
*)source
;
797 return g_cancellable_is_cancelled (cancellable_source
->cancellable
);
801 cancellable_source_dispatch (GSource
*source
,
802 GSourceFunc callback
,
805 GCancellableSourceFunc func
= (GCancellableSourceFunc
)callback
;
806 GCancellableSource
*cancellable_source
= (GCancellableSource
*)source
;
808 return (*func
) (cancellable_source
->cancellable
, user_data
);
812 cancellable_source_finalize (GSource
*source
)
814 GCancellableSource
*cancellable_source
= (GCancellableSource
*)source
;
816 if (cancellable_source
->cancellable
)
817 g_object_unref (cancellable_source
->cancellable
);
821 cancellable_source_closure_callback (GCancellable
*cancellable
,
824 GClosure
*closure
= data
;
826 GValue params
= { 0, };
827 GValue result_value
= { 0, };
830 g_value_init (&result_value
, G_TYPE_BOOLEAN
);
832 g_value_init (¶ms
, G_TYPE_CANCELLABLE
);
833 g_value_set_object (¶ms
, cancellable
);
835 g_closure_invoke (closure
, &result_value
, 1, ¶ms
, NULL
);
837 result
= g_value_get_boolean (&result_value
);
838 g_value_unset (&result_value
);
839 g_value_unset (¶ms
);
844 static GSourceFuncs cancellable_source_funcs
=
846 cancellable_source_prepare
,
847 cancellable_source_check
,
848 cancellable_source_dispatch
,
849 cancellable_source_finalize
,
850 (GSourceFunc
)cancellable_source_closure_callback
,
851 (GSourceDummyMarshal
)_gio_marshal_BOOLEAN__VOID
,
855 * g_cancellable_source_new: (skip)
856 * @cancellable: a #GCancellable, or %NULL
858 * Creates a source that triggers if @cancellable is cancelled and
859 * calls its callback of type #GCancellableSourceFunc. This is
860 * primarily useful for attaching to another (non-cancellable) source
861 * with g_source_add_child_source() to add cancellability to it.
863 * For convenience, you can call this with a %NULL #GCancellable,
864 * in which case the source will never trigger.
866 * Return value: (transfer full): the new #GSource.
871 g_cancellable_source_new (GCancellable
*cancellable
)
874 GCancellableSource
*cancellable_source
;
876 source
= g_source_new (&cancellable_source_funcs
, sizeof (GCancellableSource
));
877 g_source_set_name (source
, "GCancellable");
878 cancellable_source
= (GCancellableSource
*)source
;
880 if (g_cancellable_make_pollfd (cancellable
,
881 &cancellable_source
->pollfd
))
883 cancellable_source
->cancellable
= g_object_ref (cancellable
);
884 g_source_add_poll (source
, &cancellable_source
->pollfd
);