| /* 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, write to the |
| * Free Software Foundation, Inc., 59 Temple Place, Suite 330, |
| * Boston, MA 02111-1307, USA. |
| * |
| * Author: Alexander Larsson <alexl@redhat.com> |
| */ |
| |
| #include "config.h" |
| #ifdef HAVE_UNISTD_H |
| #include <unistd.h> |
| #endif |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <gioerror.h> |
| #ifdef G_OS_WIN32 |
| #include <windows.h> |
| #include <io.h> |
| #endif |
| #include "gcancellable.h" |
| #include "glibintl.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; |
| |
| guint fd_refcount; |
| int cancel_pipe[2]; |
| |
| #ifdef G_OS_WIN32 |
| HANDLE event; |
| #endif |
| }; |
| |
| static guint signals[LAST_SIGNAL] = { 0 }; |
| |
| G_DEFINE_TYPE (GCancellable, g_cancellable, G_TYPE_OBJECT); |
| |
| static GStaticPrivate current_cancellable = G_STATIC_PRIVATE_INIT; |
| G_LOCK_DEFINE_STATIC(cancellable); |
| static GCond *cancellable_cond = NULL; |
| |
| static void |
| g_cancellable_close_pipe (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| priv = cancellable->priv; |
| |
| if (priv->cancel_pipe[0] != -1) |
| { |
| close (priv->cancel_pipe[0]); |
| priv->cancel_pipe[0] = -1; |
| } |
| |
| if (priv->cancel_pipe[1] != -1) |
| { |
| close (priv->cancel_pipe[1]); |
| priv->cancel_pipe[1] = -1; |
| } |
| |
| #ifdef G_OS_WIN32 |
| if (priv->event) |
| { |
| CloseHandle (priv->event); |
| priv->event = NULL; |
| } |
| #endif |
| } |
| |
| static void |
| g_cancellable_finalize (GObject *object) |
| { |
| GCancellable *cancellable = G_CANCELLABLE (object); |
| |
| g_cancellable_close_pipe (cancellable); |
| |
| G_OBJECT_CLASS (g_cancellable_parent_class)->finalize (object); |
| } |
| |
| static void |
| g_cancellable_class_init (GCancellableClass *klass) |
| { |
| GObjectClass *gobject_class = G_OBJECT_CLASS (klass); |
| |
| g_type_class_add_private (klass, sizeof (GCancellablePrivate)); |
| |
| if (cancellable_cond == NULL && g_thread_supported ()) |
| cancellable_cond = g_cond_new (); |
| |
| 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 |
| * <emphasis>after</emphasis> a call to |
| * g_signal_handler_disconnect() for that handler has already |
| * returned. |
| * |
| * There is also a problem when cancellation happen |
| * 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: |
| * |[ |
| * /<!-- -->* Make sure we don't do any unnecessary work if already cancelled *<!-- -->/ |
| * if (g_cancellable_set_error_if_cancelled (cancellable)) |
| * 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); |
| |
| } |
| |
| #ifndef G_OS_WIN32 |
| static void |
| set_fd_nonblocking (int fd) |
| { |
| #ifdef F_GETFL |
| glong fcntl_flags; |
| fcntl_flags = fcntl (fd, F_GETFL); |
| |
| #ifdef O_NONBLOCK |
| fcntl_flags |= O_NONBLOCK; |
| #else |
| fcntl_flags |= O_NDELAY; |
| #endif |
| |
| fcntl (fd, F_SETFL, fcntl_flags); |
| #endif |
| } |
| |
| static void |
| set_fd_close_exec (int fd) |
| { |
| int flags; |
| |
| flags = fcntl (fd, F_GETFD, 0); |
| if (flags != -1 && (flags & FD_CLOEXEC) == 0) |
| { |
| flags |= FD_CLOEXEC; |
| fcntl (fd, F_SETFD, flags); |
| } |
| } |
| |
| |
| static void |
| g_cancellable_open_pipe (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| priv = cancellable->priv; |
| if (pipe (priv->cancel_pipe) == 0) |
| { |
| /* Make them nonblocking, just to be sure we don't block |
| * on errors and stuff |
| */ |
| set_fd_nonblocking (priv->cancel_pipe[0]); |
| set_fd_nonblocking (priv->cancel_pipe[1]); |
| set_fd_close_exec (priv->cancel_pipe[0]); |
| set_fd_close_exec (priv->cancel_pipe[1]); |
| |
| if (priv->cancelled) |
| { |
| const char ch = 'x'; |
| gssize c; |
| |
| do |
| c = write (priv->cancel_pipe[1], &ch, 1); |
| while (c == -1 && errno == EINTR); |
| } |
| } |
| } |
| #endif |
| |
| static void |
| g_cancellable_init (GCancellable *cancellable) |
| { |
| cancellable->priv = G_TYPE_INSTANCE_GET_PRIVATE (cancellable, |
| G_TYPE_CANCELLABLE, |
| GCancellablePrivate); |
| cancellable->priv->cancel_pipe[0] = -1; |
| cancellable->priv->cancel_pipe[1] = -1; |
| } |
| |
| /** |
| * 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, but not 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 |
| * cancllable can then be recieved 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_static_private_get (¤t_cancellable); |
| l = g_slist_prepend (l, cancellable); |
| g_static_private_set (¤t_cancellable, l, NULL); |
| } |
| |
| /** |
| * 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_static_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_static_private_set (¤t_cancellable, l, NULL); |
| } |
| |
| /** |
| * g_cancellable_get_current: |
| * |
| * Gets the top cancellable from the stack. |
| * |
| * Returns: 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_static_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. |
| **/ |
| void |
| g_cancellable_reset (GCancellable *cancellable) |
| { |
| GCancellablePrivate *priv; |
| |
| g_return_if_fail (G_IS_CANCELLABLE (cancellable)); |
| |
| G_LOCK(cancellable); |
| |
| priv = cancellable->priv; |
| |
| while (priv->cancelled_running) |
| { |
| priv->cancelled_running_waiting = TRUE; |
| g_cond_wait (cancellable_cond, |
| g_static_mutex_get_mutex (& G_LOCK_NAME (cancellable))); |
| } |
| |
| if (priv->cancelled) |
| { |
| /* Make sure we're not leaving old cancel state around */ |
| |
| #ifdef G_OS_WIN32 |
| if (priv->event) |
| ResetEvent (priv->event); |
| #endif |
| if (priv->cancel_pipe[0] != -1) |
| { |
| gssize c; |
| char ch; |
| |
| do |
| c = read (priv->cancel_pipe[0], &ch, 1); |
| while (c == -1 && errno == EINTR); |
| } |
| |
| priv->cancelled = FALSE; |
| } |
| G_UNLOCK(cancellable); |
| } |
| |
| /** |
| * g_cancellable_is_cancelled: |
| * @cancellable: 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; |
| } |
| |
| /** |
| * g_cancellable_set_error_if_cancelled: |
| * @cancellable: a #GCancellable object. |
| * @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)) |
| { |
| g_set_error_literal (error, |
| G_IO_ERROR, |
| G_IO_ERROR_CANCELLED, |
| _("Operation was cancelled")); |
| return TRUE; |
| } |
| |
| 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) |
| { |
| GCancellablePrivate *priv; |
| int fd; |
| |
| if (cancellable == NULL) |
| return -1; |
| |
| priv = cancellable->priv; |
| |
| #ifdef G_OS_WIN32 |
| return -1; |
| #else |
| G_LOCK(cancellable); |
| if (priv->cancel_pipe[0] == -1) |
| g_cancellable_open_pipe (cancellable); |
| fd = priv->cancel_pipe[0]; |
| if (fd != -1) |
| priv->fd_refcount++; |
| G_UNLOCK(cancellable); |
| #endif |
| |
| return fd; |
| } |
| |
| /** |
| * g_cancellable_make_pollfd: |
| * @cancellable: 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); |
| |
| { |
| #ifdef G_OS_WIN32 |
| GCancellablePrivate *priv; |
| |
| priv = cancellable->priv; |
| G_LOCK(cancellable); |
| if (priv->event == NULL) |
| { |
| /* A manual reset anonymous event, starting unset */ |
| priv->event = CreateEvent (NULL, TRUE, FALSE, NULL); |
| if (priv->event == NULL) |
| { |
| G_UNLOCK(cancellable); |
| return FALSE; |
| } |
| if (priv->cancelled) |
| SetEvent(priv->event); |
| } |
| priv->fd_refcount++; |
| G_UNLOCK(cancellable); |
| |
| pollfd->fd = (gintptr)priv->event; |
| #else /* !G_OS_WIN32 */ |
| int fd = g_cancellable_get_fd (cancellable); |
| |
| if (fd == -1) |
| return FALSE; |
| pollfd->fd = fd; |
| #endif /* G_OS_WIN32 */ |
| } |
| |
| pollfd->events = G_IO_IN; |
| pollfd->revents = 0; |
| |
| 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_LOCK (cancellable); |
| priv->fd_refcount--; |
| if (priv->fd_refcount == 0) |
| g_cancellable_close_pipe (cancellable); |
| G_UNLOCK (cancellable); |
| } |
| |
| /** |
| * 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_LOCK(cancellable); |
| if (priv->cancelled) |
| { |
| G_UNLOCK (cancellable); |
| return; |
| } |
| |
| priv->cancelled = TRUE; |
| priv->cancelled_running = TRUE; |
| #ifdef G_OS_WIN32 |
| if (priv->event) |
| SetEvent (priv->event); |
| #endif |
| if (priv->cancel_pipe[1] != -1) |
| { |
| const char ch = 'x'; |
| gssize c; |
| |
| do |
| c = write (priv->cancel_pipe[1], &ch, 1); |
| while (c == -1 && errno == EINTR); |
| } |
| G_UNLOCK(cancellable); |
| |
| g_object_ref (cancellable); |
| g_signal_emit (cancellable, signals[CANCELLED], 0); |
| |
| G_LOCK(cancellable); |
| |
| priv->cancelled_running = FALSE; |
| if (priv->cancelled_running_waiting) |
| g_cond_broadcast (cancellable_cond); |
| priv->cancelled_running_waiting = FALSE; |
| |
| G_UNLOCK(cancellable); |
| |
| g_object_unref (cancellable); |
| } |
| |
| /** |
| * g_cancellable_connect: |
| * @cancellable: A #GCancellable. |
| * @callback: The #GCallback to connect. |
| * @data: Data to pass to @callback. |
| * @data_destroy_func: 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. |
| * |
| * 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_LOCK (cancellable); |
| |
| if (cancellable->priv->cancelled) |
| { |
| void (*_callback) (GCancellable *cancellable, |
| gpointer user_data); |
| |
| _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_UNLOCK (cancellable); |
| |
| return id; |
| } |
| |
| /** |
| * g_cancellable_disconnect: |
| * @cancellable: 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_LOCK (cancellable); |
| |
| priv = cancellable->priv; |
| |
| while (priv->cancelled_running) |
| { |
| priv->cancelled_running_waiting = TRUE; |
| g_cond_wait (cancellable_cond, |
| g_static_mutex_get_mutex (& G_LOCK_NAME (cancellable))); |
| } |
| |
| g_signal_handler_disconnect (cancellable, handler_id); |
| G_UNLOCK (cancellable); |
| } |