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glib/gio/gtask.c
Philip Withnall f41ebebd34 gtask: Ignore errors from g_thread_pool_push() 
g_thread_pool_push() only returns an error if it fails to spawn a new
thread. However, it unconditionally adds the task to its worker queue,
so:
 • if _any_ threads exist in the pool, the task will eventually be
   handled; and
 • if _no_ threads exist in the pool, the task will be handled if one
   is eventually successfully spawned.
If no more threads are ever spawned, the process probably has bigger
problems than a single GTask which is taking forever to complete.

https://bugzilla.gnome.org/show_bug.cgi?id=736806
2014-09-23 08:08:45 +01:00

1821 lines
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/* GIO - GLib Input, Output and Streaming Library
*
* Copyright 2011 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/>.
*/
#include "config.h"
#include "gtask.h"
#include "gasyncresult.h"
#include "gcancellable.h"
/**
* SECTION:gtask
* @short_description: Cancellable synchronous or asynchronous task
* and result
* @include: gio/gio.h
* @see_also: #GAsyncResult
*
* A #GTask represents and manages a cancellable "task".
*
* ## Asynchronous operations
*
* The most common usage of #GTask is as a #GAsyncResult, to
* manage data during an asynchronous operation. You call
* g_task_new() in the "start" method, followed by
* g_task_set_task_data() and the like if you need to keep some
* additional data associated with the task, and then pass the
* task object around through your asynchronous operation.
* Eventually, you will call a method such as
* g_task_return_pointer() or g_task_return_error(), which will
* save the value you give it and then invoke the task's callback
* function (waiting until the next iteration of the main
* loop first, if necessary). The caller will pass the #GTask back
* to the operation's finish function (as a #GAsyncResult), and
* you can use g_task_propagate_pointer() or the like to extract
* the return value.
*
* Here is an example for using GTask as a GAsyncResult:
* |[<!-- language="C" -->
* typedef struct {
* CakeFrostingType frosting;
* char *message;
* } DecorationData;
*
* static void
* decoration_data_free (DecorationData *decoration)
* {
* g_free (decoration->message);
* g_slice_free (DecorationData, decoration);
* }
*
* static void
* baked_cb (Cake *cake,
* gpointer user_data)
* {
* GTask *task = user_data;
* DecorationData *decoration = g_task_get_task_data (task);
* GError *error = NULL;
*
* if (cake == NULL)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
* "Go to the supermarket");
* g_object_unref (task);
* return;
* }
*
* if (!cake_decorate (cake, decoration->frosting, decoration->message, &error))
* {
* g_object_unref (cake);
* // g_task_return_error() takes ownership of error
* g_task_return_error (task, error);
* g_object_unref (task);
* return;
* }
*
* g_task_return_pointer (task, cake, g_object_unref);
* g_object_unref (task);
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* GTask *task;
* DecorationData *decoration;
* Cake *cake;
*
* task = g_task_new (self, cancellable, callback, user_data);
* if (radius < 3)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_TOO_SMALL,
* "%ucm radius cakes are silly",
* radius);
* g_object_unref (task);
* return;
* }
*
* cake = _baker_get_cached_cake (self, radius, flavor, frosting, message);
* if (cake != NULL)
* {
* // _baker_get_cached_cake() returns a reffed cake
* g_task_return_pointer (task, cake, g_object_unref);
* g_object_unref (task);
* return;
* }
*
* decoration = g_slice_new (DecorationData);
* decoration->frosting = frosting;
* decoration->message = g_strdup (message);
* g_task_set_task_data (task, decoration, (GDestroyNotify) decoration_data_free);
*
* _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
* ]|
*
* ## Chained asynchronous operations
*
* #GTask also tries to simplify asynchronous operations that
* internally chain together several smaller asynchronous
* operations. g_task_get_cancellable(), g_task_get_context(),
* and g_task_get_priority() allow you to get back the task's
* #GCancellable, #GMainContext, and [I/O priority][io-priority]
* when starting a new subtask, so you don't have to keep track
* of them yourself. g_task_attach_source() simplifies the case
* of waiting for a source to fire (automatically using the correct
* #GMainContext and priority).
*
* Here is an example for chained asynchronous operations:
* |[<!-- language="C" -->
* typedef struct {
* Cake *cake;
* CakeFrostingType frosting;
* char *message;
* } BakingData;
*
* static void
* decoration_data_free (BakingData *bd)
* {
* if (bd->cake)
* g_object_unref (bd->cake);
* g_free (bd->message);
* g_slice_free (BakingData, bd);
* }
*
* static void
* decorated_cb (Cake *cake,
* GAsyncResult *result,
* gpointer user_data)
* {
* GTask *task = user_data;
* GError *error = NULL;
*
* if (!cake_decorate_finish (cake, result, &error))
* {
* g_object_unref (cake);
* g_task_return_error (task, error);
* g_object_unref (task);
* return;
* }
*
* // baking_data_free() will drop its ref on the cake, so we have to
* // take another here to give to the caller.
* g_task_return_pointer (result, g_object_ref (cake), g_object_unref);
* g_object_unref (task);
* }
*
* static void
* decorator_ready (gpointer user_data)
* {
* GTask *task = user_data;
* BakingData *bd = g_task_get_task_data (task);
*
* cake_decorate_async (bd->cake, bd->frosting, bd->message,
* g_task_get_cancellable (task),
* decorated_cb, task);
* }
*
* static void
* baked_cb (Cake *cake,
* gpointer user_data)
* {
* GTask *task = user_data;
* BakingData *bd = g_task_get_task_data (task);
* GError *error = NULL;
*
* if (cake == NULL)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
* "Go to the supermarket");
* g_object_unref (task);
* return;
* }
*
* bd->cake = cake;
*
* // Bail out now if the user has already cancelled
* if (g_task_return_error_if_cancelled (task))
* {
* g_object_unref (task);
* return;
* }
*
* if (cake_decorator_available (cake))
* decorator_ready (task);
* else
* {
* GSource *source;
*
* source = cake_decorator_wait_source_new (cake);
* // Attach @source to @task's GMainContext and have it call
* // decorator_ready() when it is ready.
* g_task_attach_source (task, source,
* G_CALLBACK (decorator_ready));
* g_source_unref (source);
* }
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* gint priority,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* GTask *task;
* BakingData *bd;
*
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_priority (task, priority);
*
* bd = g_slice_new0 (BakingData);
* bd->frosting = frosting;
* bd->message = g_strdup (message);
* g_task_set_task_data (task, bd, (GDestroyNotify) baking_data_free);
*
* _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
* ]|
*
* ## Asynchronous operations from synchronous ones
*
* You can use g_task_run_in_thread() to turn a synchronous
* operation into an asynchronous one, by running it in a thread
* which will then dispatch the result back to the caller's
* #GMainContext when it completes.
*
* Running a task in a thread:
* |[<!-- language="C" -->
* typedef struct {
* guint radius;
* CakeFlavor flavor;
* CakeFrostingType frosting;
* char *message;
* } CakeData;
*
* static void
* cake_data_free (CakeData *cake_data)
* {
* g_free (cake_data->message);
* g_slice_free (CakeData, cake_data);
* }
*
* static void
* bake_cake_thread (GTask *task,
* gpointer source_object,
* gpointer task_data,
* GCancellable *cancellable)
* {
* Baker *self = source_object;
* CakeData *cake_data = task_data;
* Cake *cake;
* GError *error = NULL;
*
* cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
* cake_data->frosting, cake_data->message,
* cancellable, &error);
* if (cake)
* g_task_return_pointer (task, cake, g_object_unref);
* else
* g_task_return_error (task, error);
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* CakeData *cake_data;
* GTask *task;
*
* cake_data = g_slice_new (CakeData);
* cake_data->radius = radius;
* cake_data->flavor = flavor;
* cake_data->frosting = frosting;
* cake_data->message = g_strdup (message);
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_run_in_thread (task, bake_cake_thread);
* g_object_unref (task);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
* ]|
*
* ## Adding cancellability to uncancellable tasks
*
* Finally, g_task_run_in_thread() and g_task_run_in_thread_sync()
* can be used to turn an uncancellable operation into a
* cancellable one. If you call g_task_set_return_on_cancel(),
* passing %TRUE, then if the task's #GCancellable is cancelled,
* it will return control back to the caller immediately, while
* allowing the task thread to continue running in the background
* (and simply discarding its result when it finally does finish).
* Provided that the task thread is careful about how it uses
* locks and other externally-visible resources, this allows you
* to make "GLib-friendly" asynchronous and cancellable
* synchronous variants of blocking APIs.
*
* Cancelling a task:
* |[<!-- language="C" -->
* static void
* bake_cake_thread (GTask *task,
* gpointer source_object,
* gpointer task_data,
* GCancellable *cancellable)
* {
* Baker *self = source_object;
* CakeData *cake_data = task_data;
* Cake *cake;
* GError *error = NULL;
*
* cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
* cake_data->frosting, cake_data->message,
* &error);
* if (error)
* {
* g_task_return_error (task, error);
* return;
* }
*
* // If the task has already been cancelled, then we don't want to add
* // the cake to the cake cache. Likewise, we don't want to have the
* // task get cancelled in the middle of updating the cache.
* // g_task_set_return_on_cancel() will return %TRUE here if it managed
* // to disable return-on-cancel, or %FALSE if the task was cancelled
* // before it could.
* if (g_task_set_return_on_cancel (task, FALSE))
* {
* // If the caller cancels at this point, their
* // GAsyncReadyCallback won't be invoked until we return,
* // so we don't have to worry that this code will run at
* // the same time as that code does. But if there were
* // other functions that might look at the cake cache,
* // then we'd probably need a GMutex here as well.
* baker_add_cake_to_cache (baker, cake);
* g_task_return_pointer (task, cake, g_object_unref);
* }
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* CakeData *cake_data;
* GTask *task;
*
* cake_data = g_slice_new (CakeData);
*
* ...
*
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_set_return_on_cancel (task, TRUE);
* g_task_run_in_thread (task, bake_cake_thread);
* }
*
* Cake *
* baker_bake_cake_sync (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GError **error)
* {
* CakeData *cake_data;
* GTask *task;
* Cake *cake;
*
* cake_data = g_slice_new (CakeData);
*
* ...
*
* task = g_task_new (self, cancellable, NULL, NULL);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_set_return_on_cancel (task, TRUE);
* g_task_run_in_thread_sync (task, bake_cake_thread);
*
* cake = g_task_propagate_pointer (task, error);
* g_object_unref (task);
* return cake;
* }
* ]|
*
* ## Porting from GSimpleAsyncResult
*
* #GTask's API attempts to be simpler than #GSimpleAsyncResult's
* in several ways:
* - You can save task-specific data with g_task_set_task_data(), and
* retrieve it later with g_task_get_task_data(). This replaces the
* abuse of g_simple_async_result_set_op_res_gpointer() for the same
* purpose with #GSimpleAsyncResult.
* - In addition to the task data, #GTask also keeps track of the
* [priority][io-priority], #GCancellable, and
* #GMainContext associated with the task, so tasks that consist of
* a chain of simpler asynchronous operations will have easy access
* to those values when starting each sub-task.
* - g_task_return_error_if_cancelled() provides simplified
* handling for cancellation. In addition, cancellation
* overrides any other #GTask return value by default, like
* #GSimpleAsyncResult does when
* g_simple_async_result_set_check_cancellable() is called.
* (You can use g_task_set_check_cancellable() to turn off that
* behavior.) On the other hand, g_task_run_in_thread()
* guarantees that it will always run your
* `task_func`, even if the task's #GCancellable
* is already cancelled before the task gets a chance to run;
* you can start your `task_func` with a
* g_task_return_error_if_cancelled() check if you need the
* old behavior.
* - The "return" methods (eg, g_task_return_pointer())
* automatically cause the task to be "completed" as well, and
* there is no need to worry about the "complete" vs "complete
* in idle" distinction. (#GTask automatically figures out
* whether the task's callback can be invoked directly, or
* if it needs to be sent to another #GMainContext, or delayed
* until the next iteration of the current #GMainContext.)
* - The "finish" functions for #GTask-based operations are generally
* much simpler than #GSimpleAsyncResult ones, normally consisting
* of only a single call to g_task_propagate_pointer() or the like.
* Since g_task_propagate_pointer() "steals" the return value from
* the #GTask, it is not necessary to juggle pointers around to
* prevent it from being freed twice.
* - With #GSimpleAsyncResult, it was common to call
* g_simple_async_result_propagate_error() from the
* `_finish()` wrapper function, and have
* virtual method implementations only deal with successful
* returns. This behavior is deprecated, because it makes it
* difficult for a subclass to chain to a parent class's async
* methods. Instead, the wrapper function should just be a
* simple wrapper, and the virtual method should call an
* appropriate `g_task_propagate_` function.
* Note that wrapper methods can now use
* g_async_result_legacy_propagate_error() to do old-style
* #GSimpleAsyncResult error-returning behavior, and
* g_async_result_is_tagged() to check if a result is tagged as
* having come from the `_async()` wrapper
* function (for "short-circuit" results, such as when passing
* 0 to g_input_stream_read_async()).
*/
/**
* GTask:
*
* The opaque object representing a synchronous or asynchronous task
* and its result.
*/
struct _GTask {
GObject parent_instance;
gpointer source_object;
gpointer source_tag;
gpointer task_data;
GDestroyNotify task_data_destroy;
GMainContext *context;
gint64 creation_time;
gint priority;
GCancellable *cancellable;
gboolean check_cancellable;
GAsyncReadyCallback callback;
gpointer callback_data;
GTaskThreadFunc task_func;
GMutex lock;
GCond cond;
gboolean return_on_cancel;
gboolean thread_cancelled;
gboolean synchronous;
gboolean thread_complete;
gboolean blocking_other_task;
GError *error;
union {
gpointer pointer;
gssize size;
gboolean boolean;
} result;
GDestroyNotify result_destroy;
gboolean result_set;
};
#define G_TASK_IS_THREADED(task) ((task)->task_func != NULL)
struct _GTaskClass
{
GObjectClass parent_class;
};
static void g_task_thread_pool_resort (void);
static void g_task_async_result_iface_init (GAsyncResultIface *iface);
static void g_task_thread_pool_init (void);
G_DEFINE_TYPE_WITH_CODE (GTask, g_task, G_TYPE_OBJECT,
G_IMPLEMENT_INTERFACE (G_TYPE_ASYNC_RESULT,
g_task_async_result_iface_init);
g_task_thread_pool_init ();)
static GThreadPool *task_pool;
static GMutex task_pool_mutex;
static GPrivate task_private = G_PRIVATE_INIT (NULL);
static void
g_task_init (GTask *task)
{
task->check_cancellable = TRUE;
}
static void
g_task_finalize (GObject *object)
{
GTask *task = G_TASK (object);
g_clear_object (&task->source_object);
g_clear_object (&task->cancellable);
if (task->context)
g_main_context_unref (task->context);
if (task->task_data_destroy)
task->task_data_destroy (task->task_data);
if (task->result_destroy && task->result.pointer)
task->result_destroy (task->result.pointer);
if (task->error)
g_error_free (task->error);
if (G_TASK_IS_THREADED (task))
{
g_mutex_clear (&task->lock);
g_cond_clear (&task->cond);
}
G_OBJECT_CLASS (g_task_parent_class)->finalize (object);
}
/**
* g_task_new:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @cancellable: (allow-none): optional #GCancellable object, %NULL to ignore.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
*
* Creates a #GTask acting on @source_object, which will eventually be
* used to invoke @callback in the current
* [thread-default main context][g-main-context-push-thread-default].
*
* Call this in the "start" method of your asynchronous method, and
* pass the #GTask around throughout the asynchronous operation. You
* can use g_task_set_task_data() to attach task-specific data to the
* object, which you can retrieve later via g_task_get_task_data().
*
* By default, if @cancellable is cancelled, then the return value of
* the task will always be %G_IO_ERROR_CANCELLED, even if the task had
* already completed before the cancellation. This allows for
* simplified handling in cases where cancellation may imply that
* other objects that the task depends on have been destroyed. If you
* do not want this behavior, you can use
* g_task_set_check_cancellable() to change it.
*
* Returns: a #GTask.
*
* Since: 2.36
*/
GTask *
g_task_new (gpointer source_object,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gpointer callback_data)
{
GTask *task;
GSource *source;
task = g_object_new (G_TYPE_TASK, NULL);
task->source_object = source_object ? g_object_ref (source_object) : NULL;
task->cancellable = cancellable ? g_object_ref (cancellable) : NULL;
task->callback = callback;
task->callback_data = callback_data;
task->context = g_main_context_ref_thread_default ();
source = g_main_current_source ();
if (source)
task->creation_time = g_source_get_time (source);
return task;
}
/**
* g_task_report_error:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
* @source_tag: an opaque pointer indicating the source of this task
* @error: (transfer full): error to report
*
* Creates a #GTask and then immediately calls g_task_return_error()
* on it. Use this in the wrapper function of an asynchronous method
* when you want to avoid even calling the virtual method. You can
* then use g_async_result_is_tagged() in the finish method wrapper to
* check if the result there is tagged as having been created by the
* wrapper method, and deal with it appropriately if so.
*
* See also g_task_report_new_error().
*
* Since: 2.36
*/
void
g_task_report_error (gpointer source_object,
GAsyncReadyCallback callback,
gpointer callback_data,
gpointer source_tag,
GError *error)
{
GTask *task;
task = g_task_new (source_object, NULL, callback, callback_data);
g_task_set_source_tag (task, source_tag);
g_task_return_error (task, error);
g_object_unref (task);
}
/**
* g_task_report_new_error:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
* @source_tag: an opaque pointer indicating the source of this task
* @domain: a #GQuark.
* @code: an error code.
* @format: a string with format characters.
* @...: a list of values to insert into @format.
*
* Creates a #GTask and then immediately calls
* g_task_return_new_error() on it. Use this in the wrapper function
* of an asynchronous method when you want to avoid even calling the
* virtual method. You can then use g_async_result_is_tagged() in the
* finish method wrapper to check if the result there is tagged as
* having been created by the wrapper method, and deal with it
* appropriately if so.
*
* See also g_task_report_error().
*
* Since: 2.36
*/
void
g_task_report_new_error (gpointer source_object,
GAsyncReadyCallback callback,
gpointer callback_data,
gpointer source_tag,
GQuark domain,
gint code,
const char *format,
...)
{
GError *error;
va_list ap;
va_start (ap, format);
error = g_error_new_valist (domain, code, format, ap);
va_end (ap);
g_task_report_error (source_object, callback, callback_data,
source_tag, error);
}
/**
* g_task_set_task_data:
* @task: the #GTask
* @task_data: (allow-none): task-specific data
* @task_data_destroy: (allow-none): #GDestroyNotify for @task_data
*
* Sets @task's task data (freeing the existing task data, if any).
*
* Since: 2.36
*/
void
g_task_set_task_data (GTask *task,
gpointer task_data,
GDestroyNotify task_data_destroy)
{
if (task->task_data_destroy)
task->task_data_destroy (task->task_data);
task->task_data = task_data;
task->task_data_destroy = task_data_destroy;
}
/**
* g_task_set_priority:
* @task: the #GTask
* @priority: the [priority][io-priority] of the request
*
* Sets @task's priority. If you do not call this, it will default to
* %G_PRIORITY_DEFAULT.
*
* This will affect the priority of #GSources created with
* g_task_attach_source() and the scheduling of tasks run in threads,
* and can also be explicitly retrieved later via
* g_task_get_priority().
*
* Since: 2.36
*/
void
g_task_set_priority (GTask *task,
gint priority)
{
task->priority = priority;
}
/**
* g_task_set_check_cancellable:
* @task: the #GTask
* @check_cancellable: whether #GTask will check the state of
* its #GCancellable for you.
*
* Sets or clears @task's check-cancellable flag. If this is %TRUE
* (the default), then g_task_propagate_pointer(), etc, and
* g_task_had_error() will check the task's #GCancellable first, and
* if it has been cancelled, then they will consider the task to have
* returned an "Operation was cancelled" error
* (%G_IO_ERROR_CANCELLED), regardless of any other error or return
* value the task may have had.
*
* If @check_cancellable is %FALSE, then the #GTask will not check the
* cancellable itself, and it is up to @task's owner to do this (eg,
* via g_task_return_error_if_cancelled()).
*
* If you are using g_task_set_return_on_cancel() as well, then
* you must leave check-cancellable set %TRUE.
*
* Since: 2.36
*/
void
g_task_set_check_cancellable (GTask *task,
gboolean check_cancellable)
{
g_return_if_fail (check_cancellable || !task->return_on_cancel);
task->check_cancellable = check_cancellable;
}
static void g_task_thread_complete (GTask *task);
/**
* g_task_set_return_on_cancel:
* @task: the #GTask
* @return_on_cancel: whether the task returns automatically when
* it is cancelled.
*
* Sets or clears @task's return-on-cancel flag. This is only
* meaningful for tasks run via g_task_run_in_thread() or
* g_task_run_in_thread_sync().
*
* If @return_on_cancel is %TRUE, then cancelling @task's
* #GCancellable will immediately cause it to return, as though the
* task's #GTaskThreadFunc had called
* g_task_return_error_if_cancelled() and then returned.
*
* This allows you to create a cancellable wrapper around an
* uninterruptable function. The #GTaskThreadFunc just needs to be
* careful that it does not modify any externally-visible state after
* it has been cancelled. To do that, the thread should call
* g_task_set_return_on_cancel() again to (atomically) set
* return-on-cancel %FALSE before making externally-visible changes;
* if the task gets cancelled before the return-on-cancel flag could
* be changed, g_task_set_return_on_cancel() will indicate this by
* returning %FALSE.
*
* You can disable and re-enable this flag multiple times if you wish.
* If the task's #GCancellable is cancelled while return-on-cancel is
* %FALSE, then calling g_task_set_return_on_cancel() to set it %TRUE
* again will cause the task to be cancelled at that point.
*
* If the task's #GCancellable is already cancelled before you call
* g_task_run_in_thread()/g_task_run_in_thread_sync(), then the
* #GTaskThreadFunc will still be run (for consistency), but the task
* will also be completed right away.
*
* Returns: %TRUE if @task's return-on-cancel flag was changed to
* match @return_on_cancel. %FALSE if @task has already been
* cancelled.
*
* Since: 2.36
*/
gboolean
g_task_set_return_on_cancel (GTask *task,
gboolean return_on_cancel)
{
g_return_val_if_fail (task->check_cancellable || !return_on_cancel, FALSE);
if (!G_TASK_IS_THREADED (task))
{
task->return_on_cancel = return_on_cancel;
return TRUE;
}
g_mutex_lock (&task->lock);
if (task->thread_cancelled)
{
if (return_on_cancel && !task->return_on_cancel)
{
g_mutex_unlock (&task->lock);
g_task_thread_complete (task);
}
else
g_mutex_unlock (&task->lock);
return FALSE;
}
task->return_on_cancel = return_on_cancel;
g_mutex_unlock (&task->lock);
return TRUE;
}
/**
* g_task_set_source_tag:
* @task: the #GTask
* @source_tag: an opaque pointer indicating the source of this task
*
* Sets @task's source tag. You can use this to tag a task return
* value with a particular pointer (usually a pointer to the function
* doing the tagging) and then later check it using
* g_task_get_source_tag() (or g_async_result_is_tagged()) in the
* task's "finish" function, to figure out if the response came from a
* particular place.
*
* Since: 2.36
*/
void
g_task_set_source_tag (GTask *task,
gpointer source_tag)
{
task->source_tag = source_tag;
}
/**
* g_task_get_source_object:
* @task: a #GTask
*
* Gets the source object from @task. Like
* g_async_result_get_source_object(), but does not ref the object.
*
* Returns: (transfer none) (type GObject): @task's source object, or %NULL
*
* Since: 2.36
*/
gpointer
g_task_get_source_object (GTask *task)
{
return task->source_object;
}
static GObject *
g_task_ref_source_object (GAsyncResult *res)
{
GTask *task = G_TASK (res);
if (task->source_object)
return g_object_ref (task->source_object);
else
return NULL;
}
/**
* g_task_get_task_data:
* @task: a #GTask
*
* Gets @task's `task_data`.
*
* Returns: (transfer none): @task's `task_data`.
*
* Since: 2.36
*/
gpointer
g_task_get_task_data (GTask *task)
{
return task->task_data;
}
/**
* g_task_get_priority:
* @task: a #GTask
*
* Gets @task's priority
*
* Returns: @task's priority
*
* Since: 2.36
*/
gint
g_task_get_priority (GTask *task)
{
return task->priority;
}
/**
* g_task_get_context:
* @task: a #GTask
*
* Gets the #GMainContext that @task will return its result in (that
* is, the context that was the
* [thread-default main context][g-main-context-push-thread-default]
* at the point when @task was created).
*
* This will always return a non-%NULL value, even if the task's
* context is the default #GMainContext.
*
* Returns: (transfer none): @task's #GMainContext
*
* Since: 2.36
*/
GMainContext *
g_task_get_context (GTask *task)
{
return task->context;
}
/**
* g_task_get_cancellable:
* @task: a #GTask
*
* Gets @task's #GCancellable
*
* Returns: (transfer none): @task's #GCancellable
*
* Since: 2.36
*/
GCancellable *
g_task_get_cancellable (GTask *task)
{
return task->cancellable;
}
/**
* g_task_get_check_cancellable:
* @task: the #GTask
*
* Gets @task's check-cancellable flag. See
* g_task_set_check_cancellable() for more details.
*
* Since: 2.36
*/
gboolean
g_task_get_check_cancellable (GTask *task)
{
return task->check_cancellable;
}
/**
* g_task_get_return_on_cancel:
* @task: the #GTask
*
* Gets @task's return-on-cancel flag. See
* g_task_set_return_on_cancel() for more details.
*
* Since: 2.36
*/
gboolean
g_task_get_return_on_cancel (GTask *task)
{
return task->return_on_cancel;
}
/**
* g_task_get_source_tag:
* @task: a #GTask
*
* Gets @task's source tag. See g_task_set_source_tag().
*
* Returns: (transfer none): @task's source tag
*
* Since: 2.36
*/
gpointer
g_task_get_source_tag (GTask *task)
{
return task->source_tag;
}
static void
g_task_return_now (GTask *task)
{
g_main_context_push_thread_default (task->context);
task->callback (task->source_object,
G_ASYNC_RESULT (task),
task->callback_data);
g_main_context_pop_thread_default (task->context);
}
static gboolean
complete_in_idle_cb (gpointer task)
{
g_task_return_now (task);
g_object_unref (task);
return FALSE;
}
typedef enum {
G_TASK_RETURN_SUCCESS,
G_TASK_RETURN_ERROR,
G_TASK_RETURN_FROM_THREAD
} GTaskReturnType;
static void
g_task_return (GTask *task,
GTaskReturnType type)
{
GSource *source;
if (type == G_TASK_RETURN_SUCCESS)
task->result_set = TRUE;
if (task->synchronous || !task->callback)
return;
/* Normally we want to invoke the task's callback when its return
* value is set. But if the task is running in a thread, then we
* want to wait until after the task_func returns, to simplify
* locking/refcounting/etc.
*/
if (G_TASK_IS_THREADED (task) && type != G_TASK_RETURN_FROM_THREAD)
return;
g_object_ref (task);
/* See if we can complete the task immediately. First, we have to be
* running inside the task's thread/GMainContext.
*/
source = g_main_current_source ();
if (source && g_source_get_context (source) == task->context)
{
/* Second, we can only complete immediately if this is not the
* same iteration of the main loop that the task was created in.
*/
if (g_source_get_time (source) > task->creation_time)
{
g_task_return_now (task);
g_object_unref (task);
return;
}
}
/* Otherwise, complete in the next iteration */
source = g_idle_source_new ();
g_task_attach_source (task, source, complete_in_idle_cb);
g_source_set_name (source, "[gio] complete_in_idle_cb");
g_source_unref (source);
}
/**
* GTaskThreadFunc:
* @task: the #GTask
* @source_object: (type GObject): @task's source object
* @task_data: @task's task data
* @cancellable: @task's #GCancellable, or %NULL
*
* The prototype for a task function to be run in a thread via
* g_task_run_in_thread() or g_task_run_in_thread_sync().
*
* If the return-on-cancel flag is set on @task, and @cancellable gets
* cancelled, then the #GTask will be completed immediately (as though
* g_task_return_error_if_cancelled() had been called), without
* waiting for the task function to complete. However, the task
* function will continue running in its thread in the background. The
* function therefore needs to be careful about how it uses
* externally-visible state in this case. See
* g_task_set_return_on_cancel() for more details.
*
* Other than in that case, @task will be completed when the
* #GTaskThreadFunc returns, not when it calls a
* `g_task_return_` function.
*
* Since: 2.36
*/
static void task_thread_cancelled (GCancellable *cancellable,
gpointer user_data);
static void
g_task_thread_complete (GTask *task)
{
g_mutex_lock (&task->lock);
if (task->thread_complete)
{
/* The task belatedly completed after having been cancelled
* (or was cancelled in the midst of being completed).
*/
g_mutex_unlock (&task->lock);
return;
}
task->thread_complete = TRUE;
if (task->blocking_other_task)
{
g_mutex_lock (&task_pool_mutex);
g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) - 1,
NULL);
g_mutex_unlock (&task_pool_mutex);
}
g_mutex_unlock (&task->lock);
if (task->cancellable)
g_signal_handlers_disconnect_by_func (task->cancellable, task_thread_cancelled, task);
if (task->synchronous)
g_cond_signal (&task->cond);
else
g_task_return (task, G_TASK_RETURN_FROM_THREAD);
}
static void
g_task_thread_pool_thread (gpointer thread_data,
gpointer pool_data)
{
GTask *task = thread_data;
g_private_set (&task_private, task);
task->task_func (task, task->source_object, task->task_data,
task->cancellable);
g_task_thread_complete (task);
g_private_set (&task_private, NULL);
g_object_unref (task);
}
static void
task_thread_cancelled (GCancellable *cancellable,
gpointer user_data)
{
GTask *task = user_data;
g_task_thread_pool_resort ();
g_mutex_lock (&task->lock);
task->thread_cancelled = TRUE;
if (!task->return_on_cancel)
{
g_mutex_unlock (&task->lock);
return;
}
/* We don't actually set task->error; g_task_return_error() doesn't
* use a lock, and g_task_propagate_error() will call
* g_cancellable_set_error_if_cancelled() anyway.
*/
g_mutex_unlock (&task->lock);
g_task_thread_complete (task);
}
static void
task_thread_cancelled_disconnect_notify (gpointer task,
GClosure *closure)
{
g_object_unref (task);
}
static void
g_task_start_task_thread (GTask *task,
GTaskThreadFunc task_func)
{
g_mutex_init (&task->lock);
g_cond_init (&task->cond);
g_mutex_lock (&task->lock);
task->task_func = task_func;
if (task->cancellable)
{
if (task->return_on_cancel &&
g_cancellable_set_error_if_cancelled (task->cancellable,
&task->error))
{
task->thread_cancelled = task->thread_complete = TRUE;
g_thread_pool_push (task_pool, g_object_ref (task), NULL);
return;
}
/* This introduces a reference count loop between the GTask and
* GCancellable, but is necessary to avoid a race on finalising the GTask
* between task_thread_cancelled() (in one thread) and
* g_task_thread_complete() (in another).
*
* Accordingly, the signal handler *must* be removed once the task has
* completed.
*/
g_signal_connect_data (task->cancellable, "cancelled",
G_CALLBACK (task_thread_cancelled),
g_object_ref (task),
task_thread_cancelled_disconnect_notify, 0);
}
g_thread_pool_push (task_pool, g_object_ref (task), NULL);
if (g_private_get (&task_private))
{
/* This thread is being spawned from another GTask thread, so
* bump up max-threads so we don't starve.
*/
g_mutex_lock (&task_pool_mutex);
if (g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) + 1,
NULL))
task->blocking_other_task = TRUE;
g_mutex_unlock (&task_pool_mutex);
}
}
/**
* g_task_run_in_thread:
* @task: a #GTask
* @task_func: a #GTaskThreadFunc
*
* Runs @task_func in another thread. When @task_func returns, @task's
* #GAsyncReadyCallback will be invoked in @task's #GMainContext.
*
* This takes a ref on @task until the task completes.
*
* See #GTaskThreadFunc for more details about how @task_func is handled.
*
* Since: 2.36
*/
void
g_task_run_in_thread (GTask *task,
GTaskThreadFunc task_func)
{
g_return_if_fail (G_IS_TASK (task));
g_object_ref (task);
g_task_start_task_thread (task, task_func);
/* The task may already be cancelled, or g_thread_pool_push() may
* have failed.
*/
if (task->thread_complete)
{
g_mutex_unlock (&task->lock);
g_task_return (task, G_TASK_RETURN_FROM_THREAD);
}
else
g_mutex_unlock (&task->lock);
g_object_unref (task);
}
/**
* g_task_run_in_thread_sync:
* @task: a #GTask
* @task_func: a #GTaskThreadFunc
*
* Runs @task_func in another thread, and waits for it to return or be
* cancelled. You can use g_task_propagate_pointer(), etc, afterward
* to get the result of @task_func.
*
* See #GTaskThreadFunc for more details about how @task_func is handled.
*
* Normally this is used with tasks created with a %NULL
* `callback`, but note that even if the task does
* have a callback, it will not be invoked when @task_func returns.
*
* Since: 2.36
*/
void
g_task_run_in_thread_sync (GTask *task,
GTaskThreadFunc task_func)
{
g_return_if_fail (G_IS_TASK (task));
g_object_ref (task);
task->synchronous = TRUE;
g_task_start_task_thread (task, task_func);
while (!task->thread_complete)
g_cond_wait (&task->cond, &task->lock);
g_mutex_unlock (&task->lock);
g_object_unref (task);
}
/**
* g_task_attach_source:
* @task: a #GTask
* @source: the source to attach
* @callback: the callback to invoke when @source triggers
*
* A utility function for dealing with async operations where you need
* to wait for a #GSource to trigger. Attaches @source to @task's
* #GMainContext with @task's [priority][io-priority], and sets @source's
* callback to @callback, with @task as the callback's `user_data`.
*
* This takes a reference on @task until @source is destroyed.
*
* Since: 2.36
*/
void
g_task_attach_source (GTask *task,
GSource *source,
GSourceFunc callback)
{
g_source_set_callback (source, callback,
g_object_ref (task), g_object_unref);
g_source_set_priority (source, task->priority);
g_source_attach (source, task->context);
}
static gboolean
g_task_propagate_error (GTask *task,
GError **error)
{
if (task->check_cancellable &&
g_cancellable_set_error_if_cancelled (task->cancellable, error))
return TRUE;
else if (task->error)
{
g_propagate_error (error, task->error);
task->error = NULL;
return TRUE;
}
else
return FALSE;
}
/**
* g_task_return_pointer:
* @task: a #GTask
* @result: (allow-none) (transfer full): the pointer result of a task
* function
* @result_destroy: (allow-none): a #GDestroyNotify function.
*
* Sets @task's result to @result and completes the task. If @result
* is not %NULL, then @result_destroy will be used to free @result if
* the caller does not take ownership of it with
* g_task_propagate_pointer().
*
* "Completes the task" means that for an ordinary asynchronous task
* it will either invoke the task's callback, or else queue that
* callback to be invoked in the proper #GMainContext, or in the next
* iteration of the current #GMainContext. For a task run via
* g_task_run_in_thread() or g_task_run_in_thread_sync(), calling this
* method will save @result to be returned to the caller later, but
* the task will not actually be completed until the #GTaskThreadFunc
* exits.
*
* Note that since the task may be completed before returning from
* g_task_return_pointer(), you cannot assume that @result is still
* valid after calling this, unless you are still holding another
* reference on it.
*
* Since: 2.36
*/
void
g_task_return_pointer (GTask *task,
gpointer result,
GDestroyNotify result_destroy)
{
g_return_if_fail (task->result_set == FALSE);
task->result.pointer = result;
task->result_destroy = result_destroy;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_pointer:
* @task: a #GTask
* @error: return location for a #GError
*
* Gets the result of @task as a pointer, and transfers ownership
* of that value to the caller.
*
* If the task resulted in an error, or was cancelled, then this will
* instead return %NULL and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: (transfer full): the task result, or %NULL on error
*
* Since: 2.36
*/
gpointer
g_task_propagate_pointer (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return NULL;
g_return_val_if_fail (task->result_set == TRUE, NULL);
task->result_destroy = NULL;
task->result_set = FALSE;
return task->result.pointer;
}
/**
* g_task_return_int:
* @task: a #GTask.
* @result: the integer (#gssize) result of a task function.
*
* Sets @task's result to @result and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Since: 2.36
*/
void
g_task_return_int (GTask *task,
gssize result)
{
g_return_if_fail (task->result_set == FALSE);
task->result.size = result;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_int:
* @task: a #GTask.
* @error: return location for a #GError
*
* Gets the result of @task as an integer (#gssize).
*
* If the task resulted in an error, or was cancelled, then this will
* instead return -1 and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: the task result, or -1 on error
*
* Since: 2.36
*/
gssize
g_task_propagate_int (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return -1;
g_return_val_if_fail (task->result_set == TRUE, -1);
task->result_set = FALSE;
return task->result.size;
}
/**
* g_task_return_boolean:
* @task: a #GTask.
* @result: the #gboolean result of a task function.
*
* Sets @task's result to @result and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Since: 2.36
*/
void
g_task_return_boolean (GTask *task,
gboolean result)
{
g_return_if_fail (task->result_set == FALSE);
task->result.boolean = result;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_boolean:
* @task: a #GTask.
* @error: return location for a #GError
*
* Gets the result of @task as a #gboolean.
*
* If the task resulted in an error, or was cancelled, then this will
* instead return %FALSE and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: the task result, or %FALSE on error
*
* Since: 2.36
*/
gboolean
g_task_propagate_boolean (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return FALSE;
g_return_val_if_fail (task->result_set == TRUE, FALSE);
task->result_set = FALSE;
return task->result.boolean;
}
/**
* g_task_return_error:
* @task: a #GTask.
* @error: (transfer full): the #GError result of a task function.
*
* Sets @task's result to @error (which @task assumes ownership of)
* and completes the task (see g_task_return_pointer() for more
* discussion of exactly what this means).
*
* Note that since the task takes ownership of @error, and since the
* task may be completed before returning from g_task_return_error(),
* you cannot assume that @error is still valid after calling this.
* Call g_error_copy() on the error if you need to keep a local copy
* as well.
*
* See also g_task_return_new_error().
*
* Since: 2.36
*/
void
g_task_return_error (GTask *task,
GError *error)
{
g_return_if_fail (task->result_set == FALSE);
g_return_if_fail (error != NULL);
task->error = error;
g_task_return (task, G_TASK_RETURN_ERROR);
}
/**
* g_task_return_new_error:
* @task: a #GTask.
* @domain: a #GQuark.
* @code: an error code.
* @format: a string with format characters.
* @...: a list of values to insert into @format.
*
* Sets @task's result to a new #GError created from @domain, @code,
* @format, and the remaining arguments, and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* See also g_task_return_error().
*
* Since: 2.36
*/
void
g_task_return_new_error (GTask *task,
GQuark domain,
gint code,
const char *format,
...)
{
GError *error;
va_list args;
va_start (args, format);
error = g_error_new_valist (domain, code, format, args);
va_end (args);
g_task_return_error (task, error);
}
/**
* g_task_return_error_if_cancelled:
* @task: a #GTask
*
* Checks if @task's #GCancellable has been cancelled, and if so, sets
* @task's error accordingly and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Returns: %TRUE if @task has been cancelled, %FALSE if not
*
* Since: 2.36
*/
gboolean
g_task_return_error_if_cancelled (GTask *task)
{
GError *error = NULL;
g_return_val_if_fail (task->result_set == FALSE, FALSE);
if (g_cancellable_set_error_if_cancelled (task->cancellable, &error))
{
/* We explicitly set task->error so this works even when
* check-cancellable is not set.
*/
g_clear_error (&task->error);
task->error = error;
g_task_return (task, G_TASK_RETURN_ERROR);
return TRUE;
}
else
return FALSE;
}
/**
* g_task_had_error:
* @task: a #GTask.
*
* Tests if @task resulted in an error.
*
* Returns: %TRUE if the task resulted in an error, %FALSE otherwise.
*
* Since: 2.36
*/
gboolean
g_task_had_error (GTask *task)
{
if (task->error != NULL)
return TRUE;
if (task->check_cancellable && g_cancellable_is_cancelled (task->cancellable))
return TRUE;
return FALSE;
}
/**
* g_task_is_valid:
* @result: (type Gio.AsyncResult): A #GAsyncResult
* @source_object: (allow-none) (type GObject): the source object
* expected to be associated with the task
*
* Checks that @result is a #GTask, and that @source_object is its
* source object (or that @source_object is %NULL and @result has no
* source object). This can be used in g_return_if_fail() checks.
*
* Returns: %TRUE if @result and @source_object are valid, %FALSE
* if not
*
* Since: 2.36
*/
gboolean
g_task_is_valid (gpointer result,
gpointer source_object)
{
if (!G_IS_TASK (result))
return FALSE;
return G_TASK (result)->source_object == source_object;
}
static gint
g_task_compare_priority (gconstpointer a,
gconstpointer b,
gpointer user_data)
{
const GTask *ta = a;
const GTask *tb = b;
gboolean a_cancelled, b_cancelled;
/* Tasks that are causing other tasks to block have higher
* priority.
*/
if (ta->blocking_other_task && !tb->blocking_other_task)
return -1;
else if (tb->blocking_other_task && !ta->blocking_other_task)
return 1;
/* Let already-cancelled tasks finish right away */
a_cancelled = (ta->check_cancellable &&
g_cancellable_is_cancelled (ta->cancellable));
b_cancelled = (tb->check_cancellable &&
g_cancellable_is_cancelled (tb->cancellable));
if (a_cancelled && !b_cancelled)
return -1;
else if (b_cancelled && !a_cancelled)
return 1;
/* Lower priority == run sooner == negative return value */
return ta->priority - tb->priority;
}
static void
g_task_thread_pool_init (void)
{
task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
10, FALSE, NULL);
g_assert (task_pool != NULL);
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}
static void
g_task_thread_pool_resort (void)
{
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}
static void
g_task_class_init (GTaskClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->finalize = g_task_finalize;
}
static gpointer
g_task_get_user_data (GAsyncResult *res)
{
return G_TASK (res)->callback_data;
}
static gboolean
g_task_is_tagged (GAsyncResult *res,
gpointer source_tag)
{
return G_TASK (res)->source_tag == source_tag;
}
static void
g_task_async_result_iface_init (GAsyncResultIface *iface)
{
iface->get_user_data = g_task_get_user_data;
iface->get_source_object = g_task_ref_source_object;
iface->is_tagged = g_task_is_tagged;
}
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