* Author: Alexander Larsson <alexl@redhat.com>
*/
-#include <config.h>
+#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>
-#ifndef pipe
-#define pipe(fds) _pipe(fds, 4096, _O_BINARY)
-#endif
#endif
#include "gcancellable.h"
#include "glibintl.h"
-#include "gioalias.h"
/**
* SECTION:gcancellable
* @short_description: Thread-safe Operation Cancellation Stack
- * @include: gio.h
+ * @include: gio/gio.h
*
* GCancellable is a thread-safe operation cancellation stack used
* throughout GIO to allow for cancellation of synchronous and
LAST_SIGNAL
};
-struct _GCancellable
+struct _GCancellablePrivate
{
- GObject parent_instance;
-
guint cancelled : 1;
- guint allocated_pipe : 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 };
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);
- if (cancellable->cancel_pipe[0] != -1)
- close (cancellable->cancel_pipe[0]);
-
- if (cancellable->cancel_pipe[1] != -1)
- close (cancellable->cancel_pipe[1]);
-
- if (G_OBJECT_CLASS (g_cancellable_parent_class)->finalize)
- (*G_OBJECT_CLASS (g_cancellable_parent_class)->finalize) (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 from another thread.
+ * 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.
*
- * Can be used by implementations of cancellable operations. This will
- * be emitted in the thread that tried to cancel the operation, not the
- * thread the is running the operation.
+ * 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"),
}
+#ifndef G_OS_WIN32
static void
set_fd_nonblocking (int fd)
{
}
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)
{
- if (pipe (cancellable->cancel_pipe) == 0)
+ 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 (cancellable->cancel_pipe[0]);
- set_fd_nonblocking (cancellable->cancel_pipe[1]);
+ 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);
+ }
}
- else
- g_warning ("Failed to create pipe for GCancellable. Out of file descriptors?");
}
+#endif
static void
g_cancellable_init (GCancellable *cancellable)
{
- cancellable->cancel_pipe[0] = -1;
- cancellable->cancel_pipe[1] = -1;
+ 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_push_current:
- * @cancellable: optional #GCancellable object, %NULL to ignore.
- *
+ * @cancellable: a #GCancellable object
+ *
* Pushes @cancellable onto the cancellable stack. The current
* cancllable can then be recieved using g_cancellable_get_current().
*
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: optional #GCancellable object, %NULL to ignore.
+ * @cancellable: a #GCancellable object
*
- * Pops @cancellable off the cancellable stack (verifying that @cancellable
+ * 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);
/**
* 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.
+ *
+ * Returns: (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_static_private_get (¤t_cancellable);
if (l == NULL)
return NULL;
void
g_cancellable_reset (GCancellable *cancellable)
{
+ GCancellablePrivate *priv;
+
g_return_if_fail (G_IS_CANCELLABLE (cancellable));
G_LOCK(cancellable);
- /* Make sure we're not leaving old cancel state around */
- if (cancellable->cancelled)
+
+ priv = cancellable->priv;
+
+ while (priv->cancelled_running)
{
- char ch;
- if (cancellable->cancel_pipe[0] != -1)
- read (cancellable->cancel_pipe[0], &ch, 1);
- cancellable->cancelled = FALSE;
+ 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);
}
gboolean
g_cancellable_is_cancelled (GCancellable *cancellable)
{
- return cancellable != NULL && cancellable->cancelled;
+ return cancellable != NULL && cancellable->priv->cancelled;
}
/**
* @cancellable: a #GCancellable object.
* @error: #GError to append error state to.
*
- * If the @cancelalble is cancelled, sets the error to notify
+ * 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.
{
if (g_cancellable_is_cancelled (cancellable))
{
- g_set_error (error,
- G_IO_ERROR,
- G_IO_ERROR_CANCELLED,
- _("Operation was cancelled"));
+ g_set_error_literal (error,
+ G_IO_ERROR,
+ G_IO_ERROR_CANCELLED,
+ _("Operation was cancelled"));
return TRUE;
}
* 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 (!cancellable->allocated_pipe)
- {
- cancellable->allocated_pipe = TRUE;
- g_cancellable_open_pipe (cancellable);
- }
-
- fd = cancellable->cancel_pipe[0];
+ 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 CANCELLED
- * signal.
+ * 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.
*
- * This function is thread-safe. In other words, you can safely call it from
- * another thread than the one running an 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)
{
- gboolean cancel;
+ GCancellablePrivate *priv;
+
+ if (cancellable == NULL ||
+ cancellable->priv->cancelled)
+ return;
+
+ priv = cancellable->priv;
- cancel = FALSE;
-
G_LOCK(cancellable);
- if (cancellable != NULL &&
- !cancellable->cancelled)
+ 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)
{
- char ch = 'x';
- cancel = TRUE;
- cancellable->cancelled = TRUE;
- if (cancellable->cancel_pipe[1] != -1)
- write (cancellable->cancel_pipe[1], &ch, 1);
+ const char ch = 'x';
+ gssize c;
+
+ do
+ c = write (priv->cancel_pipe[1], &ch, 1);
+ while (c == -1 && errno == EINTR);
}
G_UNLOCK(cancellable);
- if (cancel)
+ 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
{
- g_object_ref (cancellable);
- g_signal_emit (cancellable, signals[CANCELLED], 0);
- g_object_unref (cancellable);
+ id = g_signal_connect_data (cancellable, "cancelled",
+ callback, data,
+ (GClosureNotify) data_destroy_func,
+ 0);
}
+ G_UNLOCK (cancellable);
+
+ return id;
}
-#define __G_CANCELLABLE_C__
-#include "gioaliasdef.c"
+/**
+ * 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);
+}
projects / platform / upstream / glib.git / blobdiff