| /* GIO - GLib Input, Output and Streaming Library |
| * |
| * Copyright (C) 2006-2007 Red Hat, Inc. |
| * |
| * 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, see <http://www.gnu.org/licenses/>. |
| * |
| * Author: Alexander Larsson <alexl@redhat.com> |
| */ |
| |
| #include "config.h" |
| #include "glib.h" |
| #include <gioerror.h> |
| #include "glib-private.h" |
| #include "gcancellable.h" |
| #include "glibintl.h" |
| #ifdef G_OS_UNIX |
| #include "glib-unix.h" |
| #endif |
| |
| #include <string.h> |
| #include <errno.h> |
| |
| |
| /** |
| * SECTION:gcancellable |
| * @short_description: Thread-safe Operation Cancellation Stack |
| * @include: gio/gio.h |
| * |
| * GCancellable is a thread-safe operation cancellation stack used |
| * throughout GIO to allow for cancellation of synchronous and |
| * asynchronous operations. |
| */ |
| |
| enum { |
| CANCELLED, |
| LAST_SIGNAL |
| }; |
| |
| struct _GCancellablePrivate |
| { |
| guint cancelled : 1; |
| guint cancelled_running : 1; |
| guint cancelled_running_waiting : 1; |
| |
| union { |
| GThread *one; |
| GThread **several; |
| } critical_threads; |
| guint n_critical_threads; |
| |
| guint fd_refcount; |
| GWakeup *wakeup; |
| }; |
| |
| static guint signals[LAST_SIGNAL] = { 0 }; |
| |
| G_DEFINE_TYPE_WITH_PRIVATE (GCancellable, g_cancellable, G_TYPE_OBJECT) |
| |
| static GPrivate current_cancellable; |
| static GMutex cancellable_mutex; |
| static GCond cancellable_cond; |
| |
| static void |
| g_cancellable_finalize (GObject *object) |
| { |
| GCancellable *cancellable = G_CANCELLABLE (object); |
| |
| if (cancellable->priv->wakeup) |
| GLIB_PRIVATE_CALL (g_wakeup_free) (cancellable->priv->wakeup); |
| |
| G_OBJECT_CLASS (g_cancellable_parent_class)->finalize (object); |
| } |
| |
| static void |
| g_cancellable_class_init (GCancellableClass *klass) |
| { |
| GObjectClass *gobject_class = G_OBJECT_CLASS (klass); |
| |
| gobject_class->finalize = g_cancellable_finalize; |
| |
| /** |
| * GCancellable::cancelled: |
| * @cancellable: a #GCancellable. |
| * |
| * Emitted when the operation has been cancelled. |
| * |
| * Can be used by implementations of cancellable operations. If the |
| * operation is cancelled from another thread, the signal will be |
| * emitted in the thread that cancelled the operation, not the |
| * thread that is running the operation. |
| * |
| * Note that disconnecting from this signal (or any signal) in a |
| * multi-threaded program is prone to race conditions. For instance |
| * it is possible that a signal handler may be invoked even after |
| * a call to g_signal_handler_disconnect() for that handler has |
| * already returned. |
| * |
| * There is also a problem when cancellation happens right before |
| * connecting to the signal. If this happens the signal will |
| * unexpectedly not be emitted, and checking before connecting to |
| * the signal leaves a race condition where this is still happening. |
| * |
| * In order to make it safe and easy to connect handlers there |
| * are two helper functions: g_cancellable_connect() and |
| * g_cancellable_disconnect() which protect against problems |
| * like this. |
| * |
| * An example of how to us this: |
| * |[<!-- language="C" --> |
| * // Make sure we don't do unnecessary work if already cancelled |
| * if (g_cancellable_set_error_if_cancelled (cancellable, error)) |
| * return; |
| * |
| * // Set up all the data needed to be able to handle cancellation |
| * // of the operation |
| * my_data = my_data_new (...); |
| * |
| * id = 0; |
| * if (cancellable) |
| * id = g_cancellable_connect (cancellable, |
| * G_CALLBACK (cancelled_handler) |
| * data, NULL); |
| * |
| * // cancellable operation here... |
| * |
| * g_cancellable_disconnect (cancellable, id); |
| * |
| * // cancelled_handler is never called after this, it is now safe |
| * // to free the data |
| * my_data_free (my_data); |
| * ]| |
| * |
| * Note that the cancelled signal is emitted in the thread that |
| * the user cancelled from, which may be the main thread. So, the |
| * cancellable signal should not do something that can block. |
| */ |
| signals[CANCELLED] = |
| g_signal_new (I_("cancelled"), |
| G_TYPE_FROM_CLASS (gobject_class), |
| G_SIGNAL_RUN_LAST, |
| G_STRUCT_OFFSET (GCancellableClass, cancelled), |
| NULL, NULL, |
| g_cclosure_marshal_VOID__VOID, |
| G_TYPE_NONE, 0); |
| |
| } |
| |
| static void |
| g_cancellable_init (GCancellable *cancellable) |
| { |
| cancellable->priv = g_cancellable_get_instance_private (cancellable); |
| } |
| |
| /** |
| * g_cancellable_new: |
| * |
| * Creates a new #GCancellable object. |
| * |
| * Applications that want to start one or more operations |
| * that should be cancellable should create a #GCancellable |
| * and pass it to the operations. |
| * |
| * One #GCancellable can be used in multiple consecutive |
| * operations or in multiple concurrent operations. |
| * |
| * Returns: a #GCancellable. |
| **/ |
| GCancellable * |
| g_cancellable_new (void) |
| { |
| return g_object_new (G_TYPE_CANCELLABLE, NULL); |
| } |
| |
| /** |
| * g_cancellable_push_current: |
| * @cancellable: a #GCancellable object |
| * |
| * Pushes @cancellable onto the cancellable stack. The current |
| * cancellable can then be received using g_cancellable_get_current(). |
| * |
| * This is useful when implementing cancellable operations in |
| * code that does not allow you to pass down the cancellable object. |
| * |
| * This is typically called automatically by e.g. #GFile operations, |
| * so you rarely have to call this yourself. |
| **/ |
| void |
| g_cancellable_push_current (GCancellable *cancellable) |
| { |
| GSList *l; |
| |
| g_return_if_fail (cancellable != NULL); |
| |
| l = g_private_get (¤t_cancellable); |
| l = g_slist_prepend (l, cancellable); |
| g_private_set (¤t_cancellable, l); |
| } |
| |
| /** |
| * g_cancellable_pop_current: |
| * @cancellable: a #GCancellable object |
| * |
| * Pops @cancellable off the cancellable stack (verifying that @cancellable |
| * is on the top of the stack). |
| **/ |
| void |
| g_cancellable_pop_current (GCancellable *cancellable) |
| { |
| GSList *l; |
| |
| l = g_private_get (¤t_cancellable); |
| |
| g_return_if_fail (l != NULL); |
| g_return_if_fail (l->data == cancellable); |
| |
| l = g_slist_delete_link (l, l); |
| g_private_set (¤t_cancellable, l); |
| } |
| |
| /** |
| * g_cancellable_get_current: |
| * |
| * Gets the top cancellable from the stack. |
| * |
| * Returns: (nullable) (transfer none): a #GCancellable from the top |
| * of the stack, or %NULL if the stack is empty. |
| **/ |
| GCancellable * |
| g_cancellable_get_current (void) |
| { |
| GSList *l; |
| |
| l = g_private_get (¤t_cancellable); |
| if (l == NULL) |
| return NULL; |
| |
| return G_CANCELLABLE (l->data); |
| } |
| |
| /** |
| * g_cancellable_reset: |
| * @cancellable: a #GCancellable object. |
| * |
| * Resets @cancellable to its uncancelled state. |
| * |
| * If cancellable is currently in use by any cancellable operation |
| * then the behavior of this function is undefined. |
| * |
| * Note that it is generally not a good idea to reuse an existing |
| * cancellable for more operations after it has been cancelled once, |
| * as this function might tempt you to do. The recommended practice |
| * is to drop the reference to a cancellable after cancelling it, |
| * and let it die with the outstanding async operations. You should |
| * create a fresh cancellable for further async operations. |
| **/ |
| void |
| g_cancellable_reset (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| g_return_if_fail (G_IS_CANCELLABLE (cancellable)); |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| priv = cancellable->priv; |
| |
| while (priv->cancelled_running) |
| { |
| priv->cancelled_running_waiting = TRUE; |
| g_cond_wait (&cancellable_cond, &cancellable_mutex); |
| } |
| |
| if (priv->cancelled) |
| { |
| if (priv->wakeup) |
| GLIB_PRIVATE_CALL (g_wakeup_acknowledge) (priv->wakeup); |
| |
| priv->cancelled = FALSE; |
| } |
| |
| g_mutex_unlock (&cancellable_mutex); |
| } |
| |
| /** |
| * g_cancellable_is_cancelled: |
| * @cancellable: (allow-none): a #GCancellable or %NULL |
| * |
| * Checks if a cancellable job has been cancelled. |
| * |
| * Returns: %TRUE if @cancellable is cancelled, |
| * FALSE if called with %NULL or if item is not cancelled. |
| **/ |
| gboolean |
| g_cancellable_is_cancelled (GCancellable *cancellable) |
| { |
| return cancellable != NULL && cancellable->priv->cancelled; |
| } |
| |
| static gboolean |
| g_cancellable_set_error (GError **error) |
| { |
| g_set_error_literal (error, |
| G_IO_ERROR, |
| G_IO_ERROR_CANCELLED, |
| _("Operation was cancelled")); |
| return FALSE; |
| } |
| |
| /** |
| * g_cancellable_set_error_if_cancelled: |
| * @cancellable: (allow-none): a #GCancellable or %NULL |
| * @error: #GError to append error state to |
| * |
| * If the @cancellable is cancelled, sets the error to notify |
| * that the operation was cancelled. |
| * |
| * Returns: %TRUE if @cancellable was cancelled, %FALSE if it was not |
| */ |
| gboolean |
| g_cancellable_set_error_if_cancelled (GCancellable *cancellable, |
| GError **error) |
| { |
| if (g_cancellable_is_cancelled (cancellable)) |
| return !g_cancellable_set_error (error); |
| |
| return FALSE; |
| } |
| |
| /** |
| * g_cancellable_get_fd: |
| * @cancellable: a #GCancellable. |
| * |
| * Gets the file descriptor for a cancellable job. This can be used to |
| * implement cancellable operations on Unix systems. The returned fd will |
| * turn readable when @cancellable is cancelled. |
| * |
| * You are not supposed to read from the fd yourself, just check for |
| * readable status. Reading to unset the readable status is done |
| * with g_cancellable_reset(). |
| * |
| * After a successful return from this function, you should use |
| * g_cancellable_release_fd() to free up resources allocated for |
| * the returned file descriptor. |
| * |
| * See also g_cancellable_make_pollfd(). |
| * |
| * Returns: A valid file descriptor. %-1 if the file descriptor |
| * is not supported, or on errors. |
| **/ |
| int |
| g_cancellable_get_fd (GCancellable *cancellable) |
| { |
| GPollFD pollfd; |
| |
| if (cancellable == NULL) |
| return -1; |
| |
| #ifdef G_OS_WIN32 |
| pollfd.fd = -1; |
| #else |
| g_cancellable_make_pollfd (cancellable, &pollfd); |
| #endif |
| |
| return pollfd.fd; |
| } |
| |
| /** |
| * g_cancellable_make_pollfd: |
| * @cancellable: (allow-none): a #GCancellable or %NULL |
| * @pollfd: a pointer to a #GPollFD |
| * |
| * Creates a #GPollFD corresponding to @cancellable; this can be passed |
| * to g_poll() and used to poll for cancellation. This is useful both |
| * for unix systems without a native poll and for portability to |
| * windows. |
| * |
| * When this function returns %TRUE, you should use |
| * g_cancellable_release_fd() to free up resources allocated for the |
| * @pollfd. After a %FALSE return, do not call g_cancellable_release_fd(). |
| * |
| * If this function returns %FALSE, either no @cancellable was given or |
| * resource limits prevent this function from allocating the necessary |
| * structures for polling. (On Linux, you will likely have reached |
| * the maximum number of file descriptors.) The suggested way to handle |
| * these cases is to ignore the @cancellable. |
| * |
| * You are not supposed to read from the fd yourself, just check for |
| * readable status. Reading to unset the readable status is done |
| * with g_cancellable_reset(). |
| * |
| * Returns: %TRUE if @pollfd was successfully initialized, %FALSE on |
| * failure to prepare the cancellable. |
| * |
| * Since: 2.22 |
| **/ |
| gboolean |
| g_cancellable_make_pollfd (GCancellable *cancellable, GPollFD *pollfd) |
| { |
| g_return_val_if_fail (pollfd != NULL, FALSE); |
| if (cancellable == NULL) |
| return FALSE; |
| g_return_val_if_fail (G_IS_CANCELLABLE (cancellable), FALSE); |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| cancellable->priv->fd_refcount++; |
| |
| if (cancellable->priv->wakeup == NULL) |
| { |
| cancellable->priv->wakeup = GLIB_PRIVATE_CALL (g_wakeup_new) (); |
| |
| if (cancellable->priv->cancelled) |
| GLIB_PRIVATE_CALL (g_wakeup_signal) (cancellable->priv->wakeup); |
| } |
| |
| GLIB_PRIVATE_CALL (g_wakeup_get_pollfd) (cancellable->priv->wakeup, pollfd); |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| return TRUE; |
| } |
| |
| /** |
| * g_cancellable_release_fd: |
| * @cancellable: a #GCancellable |
| * |
| * Releases a resources previously allocated by g_cancellable_get_fd() |
| * or g_cancellable_make_pollfd(). |
| * |
| * For compatibility reasons with older releases, calling this function |
| * is not strictly required, the resources will be automatically freed |
| * when the @cancellable is finalized. However, the @cancellable will |
| * block scarce file descriptors until it is finalized if this function |
| * is not called. This can cause the application to run out of file |
| * descriptors when many #GCancellables are used at the same time. |
| * |
| * Since: 2.22 |
| **/ |
| void |
| g_cancellable_release_fd (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| if (cancellable == NULL) |
| return; |
| |
| g_return_if_fail (G_IS_CANCELLABLE (cancellable)); |
| g_return_if_fail (cancellable->priv->fd_refcount > 0); |
| |
| priv = cancellable->priv; |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| priv->fd_refcount--; |
| if (priv->fd_refcount == 0) |
| { |
| GLIB_PRIVATE_CALL (g_wakeup_free) (priv->wakeup); |
| priv->wakeup = NULL; |
| } |
| |
| g_mutex_unlock (&cancellable_mutex); |
| } |
| |
| /** |
| * g_cancellable_wait_for_handle: |
| * @cancellable: (nullable): a #GCancellable object |
| * @handle: the handle to wait for, or %G_HANDLE_NULL |
| * @ready_time: the monotonic time past which to return |
| * @error: a pointer to a %NULL #GError, or %NULL |
| * |
| * Waits on @handle until @handle is ready, until the @ready_time is |
| * reached, or until @cancellable is cancelled. |
| * |
| * If @cancellable is cancelled or if polling returns an error then |
| * @error will be set and %FALSE will be returned. |
| * |
| * If the handle becomes ready then %TRUE will be returned. |
| * |
| * If @ready_time passes, %G_IO_ERROR_TIMED_OUT will be returned. A |
| * ready time in the past (ideally 0) means to return immediately and a |
| * ready time of -1 means to block indefinitely. |
| * |
| * Interruptions due to signal delivery on POSIX (`EINTR`), or async |
| * procedure calls or IO completion handlers on Windows |
| * (`WAIT_IO_COMPLETION`) are dealt with internally by rescheduling the |
| * wait. |
| * |
| * If you are on POSIX and need to check for specific IO conditions, use |
| * g_cancellable_wait_for_unix_fd(). |
| * |
| * If @handle is %G_HANDLE_NULL and ready_time is 0 then this function |
| * only checks for cancellation and returns immediately (successfully) |
| * otherwise. It is not valid to use %G_HANDLE_NULL with a non-zero |
| * @ready_time. |
| * |
| * Returns: %TRUE if @handle became ready, |
| * otherwise %FALSE with @error set |
| * |
| * Since: 2.44 |
| */ |
| gboolean |
| g_cancellable_wait_for_handle (GCancellable *cancellable, |
| ghandle handle, |
| gint64 ready_time, |
| GError **error) |
| { |
| ghandle handles[2]; |
| GThread *self; |
| gint result; |
| |
| g_return_val_if_fail (g_handle_is_valid (handle) || ready_time == 0, FALSE); |
| |
| /* save ourselves the trouble of entering the critical section */ |
| if (ready_time == 0) |
| { |
| if (g_cancellable_set_error_if_cancelled (cancellable, error)) |
| return FALSE; |
| |
| if (!g_handle_is_valid (handle)) |
| return TRUE; |
| } |
| |
| if (!cancellable) |
| return g_handle_wait_multiple (&handle, 1, ready_time, error); |
| |
| /* OK: now we do the "full strength version" */ |
| self = g_thread_self (); |
| handles[0] = g_cancellable_enter_critical_section_using_handle (cancellable, self, error); |
| if (!g_handle_is_valid (handles[0])) |
| return FALSE; |
| |
| handles[1] = handle; |
| |
| /* result will be -1, 0 or 1 */ |
| result = g_handle_wait_multiple (handles, 2, ready_time, error); |
| |
| /* This is the case where we had a cancellation from another thread */ |
| if (result == 0) |
| g_cancellable_set_error (error); |
| |
| /* Otherwise, for -1 we already have an error set and '1' is success */ |
| g_cancellable_leave_critical_section (cancellable, self, NULL); |
| |
| return (result == 1); |
| } |
| |
| /** |
| * g_cancellable_wait_for_unix_fd: |
| * @cancellable: (nullable): a #GCancellable object |
| * @fd: a file descriptor, or -1 |
| * @condition: the condition to wait for |
| * @ready_time: the monotonic time past which to return |
| * @error: a pointer to a %NULL #GError, or %NULL |
| * |
| * Waits on @handle until the requested condition is met, until the |
| * @ready_time is reached, or until @cancellable is cancelled. |
| * |
| * This function is equivalent to g_cancellable_wait_for_handle(). The |
| * only difference is that it takes @condition and that is is only |
| * available on POSIX. |
| * |
| * If @fd is -1 and ready_time is 0 then this function only checks for |
| * cancellation and returns immediately (successfully) otherwise. It is |
| * not valid to use an @fd of -1 with a non-zero @ready_time. |
| * |
| * Returns: %TRUE if @handle became ready, |
| * otherwise %FALSE with @error set |
| * |
| * Since: 2.44 |
| */ |
| #ifdef G_OS_UNIX |
| gboolean |
| g_cancellable_wait_for_unix_fd (GCancellable *cancellable, |
| gint fd, |
| GIOCondition condition, |
| gint64 ready_time, |
| GError **error) |
| { |
| GPollFD pollfds[2]; |
| GThread *self; |
| gint result; |
| |
| g_return_val_if_fail (fd != -1 || ready_time == 0, FALSE); |
| |
| /* save ourselves the trouble of entering the critical section */ |
| if (ready_time == 0) |
| { |
| if (g_cancellable_set_error_if_cancelled (cancellable, error)) |
| return FALSE; |
| |
| if (fd == -1) |
| return TRUE; |
| } |
| |
| pollfds[1].fd = fd; |
| pollfds[1].events = condition; |
| |
| if (!cancellable) |
| return g_unix_fd_wait_multiple (&pollfds[1], 1, ready_time, error); |
| |
| /* OK: now we do the "full strength version" */ |
| self = g_thread_self (); |
| pollfds[0].fd = g_cancellable_enter_critical_section_using_handle (cancellable, self, error); |
| pollfds[0].events = G_IO_IN; |
| |
| if (pollfds[0].fd == -1) |
| return FALSE; |
| |
| /* result will be -1, 0 or 1 */ |
| result = g_unix_fd_wait_multiple (pollfds, 2, ready_time, error); |
| |
| /* This is the case where we had a cancellation from another thread */ |
| if (result == 0) |
| g_cancellable_set_error (error); |
| |
| /* Otherwise, for -1 we already have an error set and '1' is success */ |
| g_cancellable_leave_critical_section (cancellable, self, NULL); |
| |
| return (result == 1); |
| } |
| #endif |
| |
| /** |
| * g_cancellable_cancel: |
| * @cancellable: a #GCancellable object. |
| * |
| * Will set @cancellable to cancelled, and will emit the |
| * #GCancellable::cancelled signal. (However, see the warning about |
| * race conditions in the documentation for that signal if you are |
| * planning to connect to it.) |
| * |
| * This function is thread-safe. In other words, you can safely call |
| * it from a thread other than the one running the operation that was |
| * passed the @cancellable. |
| * |
| * The convention within gio is that cancelling an asynchronous |
| * operation causes it to complete asynchronously. That is, if you |
| * cancel the operation from the same thread in which it is running, |
| * then the operation's #GAsyncReadyCallback will not be invoked until |
| * the application returns to the main loop. |
| **/ |
| void |
| g_cancellable_cancel (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| if (cancellable == NULL || |
| cancellable->priv->cancelled) |
| return; |
| |
| priv = cancellable->priv; |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| if (priv->cancelled) |
| { |
| g_mutex_unlock (&cancellable_mutex); |
| return; |
| } |
| |
| priv->cancelled = TRUE; |
| priv->cancelled_running = TRUE; |
| |
| /* wake threads in critical sections */ |
| if G_UNLIKELY (cancellable->priv->n_critical_threads > 1) |
| { |
| guint i; |
| |
| for (i = 0; i < cancellable->priv->n_critical_threads; i++) |
| g_thread_wakeup (cancellable->priv->critical_threads.several[i]); |
| } |
| else if (cancellable->priv->n_critical_threads) |
| g_thread_wakeup (cancellable->priv->critical_threads.one); |
| |
| if (priv->wakeup) |
| GLIB_PRIVATE_CALL (g_wakeup_signal) (priv->wakeup); |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| g_object_ref (cancellable); |
| g_signal_emit (cancellable, signals[CANCELLED], 0); |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| priv->cancelled_running = FALSE; |
| if (priv->cancelled_running_waiting) |
| g_cond_broadcast (&cancellable_cond); |
| priv->cancelled_running_waiting = FALSE; |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| g_object_unref (cancellable); |
| } |
| |
| /** |
| * g_cancellable_connect: |
| * @cancellable: A #GCancellable. |
| * @callback: The #GCallback to connect. |
| * @data: Data to pass to @callback. |
| * @data_destroy_func: (allow-none): Free function for @data or %NULL. |
| * |
| * Convenience function to connect to the #GCancellable::cancelled |
| * signal. Also handles the race condition that may happen |
| * if the cancellable is cancelled right before connecting. |
| * |
| * @callback is called at most once, either directly at the |
| * time of the connect if @cancellable is already cancelled, |
| * or when @cancellable is cancelled in some thread. |
| * |
| * @data_destroy_func will be called when the handler is |
| * disconnected, or immediately if the cancellable is already |
| * cancelled. |
| * |
| * See #GCancellable::cancelled for details on how to use this. |
| * |
| * Since GLib 2.40, the lock protecting @cancellable is not held when |
| * @callback is invoked. This lifts a restriction in place for |
| * earlier GLib versions which now makes it easier to write cleanup |
| * code that unconditionally invokes e.g. g_cancellable_cancel(). |
| * |
| * Returns: The id of the signal handler or 0 if @cancellable has already |
| * been cancelled. |
| * |
| * Since: 2.22 |
| */ |
| gulong |
| g_cancellable_connect (GCancellable *cancellable, |
| GCallback callback, |
| gpointer data, |
| GDestroyNotify data_destroy_func) |
| { |
| gulong id; |
| |
| g_return_val_if_fail (G_IS_CANCELLABLE (cancellable), 0); |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| if (cancellable->priv->cancelled) |
| { |
| void (*_callback) (GCancellable *cancellable, |
| gpointer user_data); |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| _callback = (void *)callback; |
| id = 0; |
| |
| _callback (cancellable, data); |
| |
| if (data_destroy_func) |
| data_destroy_func (data); |
| } |
| else |
| { |
| id = g_signal_connect_data (cancellable, "cancelled", |
| callback, data, |
| (GClosureNotify) data_destroy_func, |
| 0); |
| |
| g_mutex_unlock (&cancellable_mutex); |
| } |
| |
| |
| return id; |
| } |
| |
| /** |
| * g_cancellable_disconnect: |
| * @cancellable: (allow-none): A #GCancellable or %NULL. |
| * @handler_id: Handler id of the handler to be disconnected, or %0. |
| * |
| * Disconnects a handler from a cancellable instance similar to |
| * g_signal_handler_disconnect(). Additionally, in the event that a |
| * signal handler is currently running, this call will block until the |
| * handler has finished. Calling this function from a |
| * #GCancellable::cancelled signal handler will therefore result in a |
| * deadlock. |
| * |
| * This avoids a race condition where a thread cancels at the |
| * same time as the cancellable operation is finished and the |
| * signal handler is removed. See #GCancellable::cancelled for |
| * details on how to use this. |
| * |
| * If @cancellable is %NULL or @handler_id is %0 this function does |
| * nothing. |
| * |
| * Since: 2.22 |
| */ |
| void |
| g_cancellable_disconnect (GCancellable *cancellable, |
| gulong handler_id) |
| { |
| GCancellablePrivate *priv; |
| |
| if (handler_id == 0 || cancellable == NULL) |
| return; |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| priv = cancellable->priv; |
| |
| while (priv->cancelled_running) |
| { |
| priv->cancelled_running_waiting = TRUE; |
| g_cond_wait (&cancellable_cond, &cancellable_mutex); |
| } |
| |
| g_signal_handler_disconnect (cancellable, handler_id); |
| |
| g_mutex_unlock (&cancellable_mutex); |
| } |
| |
| typedef struct { |
| GSource source; |
| |
| GCancellable *cancellable; |
| guint cancelled_handler; |
| } GCancellableSource; |
| |
| static void |
| cancellable_source_cancelled (GCancellable *cancellable, |
| gpointer user_data) |
| { |
| GSource *source = user_data; |
| |
| if (!g_source_is_destroyed (source)) |
| g_source_set_ready_time (source, 0); |
| } |
| |
| static gboolean |
| cancellable_source_dispatch (GSource *source, |
| GSourceFunc callback, |
| gpointer user_data) |
| { |
| GCancellableSourceFunc func = (GCancellableSourceFunc)callback; |
| GCancellableSource *cancellable_source = (GCancellableSource *)source; |
| |
| g_source_set_ready_time (source, -1); |
| return (*func) (cancellable_source->cancellable, user_data); |
| } |
| |
| static void |
| cancellable_source_finalize (GSource *source) |
| { |
| GCancellableSource *cancellable_source = (GCancellableSource *)source; |
| |
| if (cancellable_source->cancellable) |
| { |
| g_cancellable_disconnect (cancellable_source->cancellable, |
| cancellable_source->cancelled_handler); |
| g_object_unref (cancellable_source->cancellable); |
| } |
| } |
| |
| static gboolean |
| cancellable_source_closure_callback (GCancellable *cancellable, |
| gpointer data) |
| { |
| GClosure *closure = data; |
| |
| GValue params = G_VALUE_INIT; |
| GValue result_value = G_VALUE_INIT; |
| gboolean result; |
| |
| g_value_init (&result_value, G_TYPE_BOOLEAN); |
| |
| g_value_init (¶ms, G_TYPE_CANCELLABLE); |
| g_value_set_object (¶ms, cancellable); |
| |
| g_closure_invoke (closure, &result_value, 1, ¶ms, NULL); |
| |
| result = g_value_get_boolean (&result_value); |
| g_value_unset (&result_value); |
| g_value_unset (¶ms); |
| |
| return result; |
| } |
| |
| static GSourceFuncs cancellable_source_funcs = |
| { |
| NULL, |
| NULL, |
| cancellable_source_dispatch, |
| cancellable_source_finalize, |
| (GSourceFunc)cancellable_source_closure_callback, |
| }; |
| |
| /** |
| * g_cancellable_source_new: (skip) |
| * @cancellable: (allow-none): a #GCancellable, or %NULL |
| * |
| * Creates a source that triggers if @cancellable is cancelled and |
| * calls its callback of type #GCancellableSourceFunc. This is |
| * primarily useful for attaching to another (non-cancellable) source |
| * with g_source_add_child_source() to add cancellability to it. |
| * |
| * For convenience, you can call this with a %NULL #GCancellable, |
| * in which case the source will never trigger. |
| * |
| * The new #GSource will hold a reference to the #GCancellable. |
| * |
| * Returns: (transfer full): the new #GSource. |
| * |
| * Since: 2.28 |
| */ |
| GSource * |
| g_cancellable_source_new (GCancellable *cancellable) |
| { |
| GSource *source; |
| GCancellableSource *cancellable_source; |
| |
| source = g_source_new (&cancellable_source_funcs, sizeof (GCancellableSource)); |
| g_source_set_name (source, "GCancellable"); |
| cancellable_source = (GCancellableSource *)source; |
| |
| if (cancellable) |
| { |
| cancellable_source->cancellable = g_object_ref (cancellable); |
| |
| /* We intentionally don't use g_cancellable_connect() here, |
| * because we don't want the "at most once" behavior. |
| */ |
| cancellable_source->cancelled_handler = |
| g_signal_connect (cancellable, "cancelled", |
| G_CALLBACK (cancellable_source_cancelled), |
| source); |
| if (g_cancellable_is_cancelled (cancellable)) |
| g_source_set_ready_time (source, 0); |
| } |
| |
| return source; |
| } |
| |
| static void |
| g_cancellable_add_critical_thread (GCancellable *cancellable, |
| GThread *thread) |
| { |
| g_thread_ref (thread); |
| |
| /* The vast majority case will be when there is only one thread, but |
| * we do support a single cancellable in use from multiple threads and |
| * they may all be using critical-section handling. |
| */ |
| if G_LIKELY (cancellable->priv->n_critical_threads == 0) |
| { |
| cancellable->priv->critical_threads.one = thread; |
| cancellable->priv->n_critical_threads = 1; |
| } |
| else if (cancellable->priv->n_critical_threads == 1) |
| { |
| GThread *other = cancellable->priv->critical_threads.one; |
| |
| cancellable->priv->critical_threads.several = g_new (GThread *, 2); |
| cancellable->priv->critical_threads.several[0] = other; |
| cancellable->priv->critical_threads.several[1] = thread; |
| cancellable->priv->n_critical_threads = 2; |
| } |
| else |
| { |
| GThread **threads; |
| guint i; |
| |
| threads = g_new (GThread *, cancellable->priv->n_critical_threads + 1); |
| |
| for (i = 0; i < cancellable->priv->n_critical_threads; i++) |
| { |
| g_assert (cancellable->priv->critical_threads.several[i] != thread); |
| threads[i] = cancellable->priv->critical_threads.several[i]; |
| } |
| |
| threads[i++] = thread; |
| |
| g_free (cancellable->priv->critical_threads.several); |
| cancellable->priv->critical_threads.several = threads; |
| cancellable->priv->n_critical_threads++; |
| } |
| } |
| |
| static void |
| g_cancellable_remove_critical_thread (GCancellable *cancellable, |
| GThread *thread) |
| { |
| if G_LIKELY (cancellable->priv->n_critical_threads == 1) |
| { |
| g_assert (cancellable->priv->critical_threads.one == thread); |
| cancellable->priv->n_critical_threads = 0; |
| } |
| else if (cancellable->priv->n_critical_threads == 2) |
| { |
| GThread *other; |
| |
| if (cancellable->priv->critical_threads.several[0] != thread) |
| { |
| g_assert (cancellable->priv->critical_threads.several[0] == thread); |
| other = cancellable->priv->critical_threads.several[0]; |
| } |
| else |
| other = cancellable->priv->critical_threads.several[1]; |
| |
| g_free (cancellable->priv->critical_threads.several); |
| cancellable->priv->critical_threads.one = other; |
| cancellable->priv->n_critical_threads = 1; |
| } |
| else |
| { |
| guint i; |
| |
| for (i = 0; i < cancellable->priv->n_critical_threads; i++) |
| if (cancellable->priv->critical_threads.several[i] == thread) |
| break; |
| |
| g_assert (i != cancellable->priv->n_critical_threads); |
| cancellable->priv->n_critical_threads--; |
| |
| for (; i < cancellable->priv->n_critical_threads; i++) |
| /* move from the right */ |
| cancellable->priv->critical_threads.several[i] = cancellable->priv->critical_threads.several[i + 1]; |
| } |
| |
| g_thread_unref (thread); |
| } |
| |
| /** |
| * g_cancellable_enter_critical_section_using_handle: |
| * @cancellable: (nullable): a #GCancellable, or %NULL |
| * @thread: the current #GThread |
| * @error: a pointer to a %NULL #GError, or %NULL |
| * |
| * Attempts to enter a critical section that can be cancelled by |
| * @cancellable. |
| * |
| * See g_thread_enter_critical_section_using_handle() for a conceptual |
| * introduction. |
| * |
| * @thread absolutely must be equal to the current thread as returned by |
| * g_thread_self(). The behaviour is completely undefined otherwise. |
| * |
| * This function is essentially a convenience wrapper. First, it |
| * atomically checks for cancellation and returns %G_HANDLE_NULL with |
| * @error appropriately set if the cancellable is already cancelled. |
| * Then it sets up @cancellable so that a cancellation in another thread |
| * will result in g_thread_wakeup() being called on @thread. Finally, |
| * g_thread_enter_critical_section_using_handle() is called and the |
| * result is returned. |
| * |
| * You cannot call g_thread_wakeup() on @thread for yourself because you |
| * cannot acquire the lock that this function will use the establish the |
| * critical section. |
| * |
| * The overall result is that the returned handle will poll as ready if |
| * @cancellable is triggered. |
| * |
| * You must call g_cancellable_leave_critical_section() when you are |
| * done. |
| * |
| * If @cancellable is %NULL then this function will still enter the |
| * critical section and return a valid handle, but that handle will |
| * never become ready. This is relatively low-overhead but you could |
| * save yourself the trouble of polling on an extra object by checking |
| * for @cancellable being %NULL before calling this function. |
| * |
| * The example in the documentation for |
| * g_thread_enter_critical_section_using_handle() could be written |
| * using GCancellable as follows: |
| * |
| * |[ |
| * static gpointer worker (gpointer user_data) { |
| * GCancellable *cancellable = user_data; |
| * GThread *self = g_thread_self (); |
| * |
| * while (TRUE) |
| * { |
| * ghandle handle; |
| * |
| * handle = g_cancellable_enter_critical_section_using_handle (cancellable, self, NULL); |
| * if (!g_handle_is_valid (handle)) |
| * break; |
| * |
| * do_blocking_work (handle); |
| * |
| * g_cancellable_leave_critical_section (cancellable, self, NULL); |
| * } |
| * |
| * return NULL; |
| * } |
| * |
| * void start_cancellable_worker (GCancellable *cancellable) { |
| * g_thread_unref (g_thread_new ("worker", worker, cancellable)); |
| * } |
| * ]| |
| * |
| * Returns: a valid #ghandle if the critical section was entered or |
| * %G_HANDLE_NULL (and @error set) if not. Use g_handle_is_valid() to |
| * check. |
| * |
| * Since: 2.44 |
| */ |
| ghandle |
| g_cancellable_enter_critical_section_using_handle (GCancellable *cancellable, |
| GThread *thread, |
| GError **error) |
| { |
| ghandle result = G_HANDLE_NULL; |
| |
| /* We're about to call a function that is documented as requiring a |
| * lock to be held... without holding a lock. |
| * |
| * That's actually OK because we're operating on thread-local data and |
| * there is no chance that g_thread_wakeup() can be called if the |
| * cancellable is %NULL. |
| */ |
| if (!cancellable) |
| return g_thread_enter_critical_section_using_handle (thread); |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| if (!cancellable->priv->cancelled) |
| { |
| result = g_thread_enter_critical_section_using_handle (thread); |
| g_cancellable_add_critical_thread (cancellable, thread); |
| } |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| if (!g_handle_is_valid (result)) |
| g_cancellable_set_error (error); |
| |
| return result; |
| } |
| |
| /** |
| * g_cancellable_leave_critical_section: |
| * @cancellable: (nullable): a #GCancellable, or %NULL |
| * @thread: the current #GThread |
| * @error: a pointer to a %NULL #GError, or %NULL |
| * |
| * Leaves the critical section entered by |
| * g_cancellable_enter_critical_section_using_handle(). |
| * |
| * This will also check @cancellable again for having been cancelled |
| * (which may very well be the reason for the operating in the critical |
| * section having finished). This provides a convenient chance to |
| * recheck @cancellable, but you may safely ignore the result if you |
| * will be checking it again soon anyway. |
| * |
| * Returns: %TRUE if @cancellable was not cancelled. Returns %FALSE |
| * (with @error set appropriately) in case of cancellation. |
| * |
| * Since: 2.44 |
| */ |
| gboolean |
| g_cancellable_leave_critical_section (GCancellable *cancellable, |
| GThread *thread, |
| GError **error) |
| { |
| gboolean success = TRUE; |
| |
| /* See comment above */ |
| if (!cancellable) |
| { |
| g_thread_leave_critical_section (thread); |
| return TRUE; |
| } |
| |
| g_mutex_lock (&cancellable_mutex); |
| |
| g_cancellable_remove_critical_thread (cancellable, thread); |
| g_thread_leave_critical_section (thread); |
| success = !cancellable->priv->cancelled; |
| |
| g_mutex_unlock (&cancellable_mutex); |
| |
| if (!success) |
| return g_cancellable_set_error (error); |
| |
| return TRUE; |
| } |