luc14n0/glib
1
0
Fork 0
mirror of https://gitlab.gnome.org/GNOME/glib.git synced 2025-10-31 08:22:16 +01:00
Code Issues Packages Projects Releases Wiki Activity
Files
c537ffd4a522d41b352a88b8310b9b182c0c13ea
glib/gio/gtask.c
Mavroudis Chatzilazaridis cb1502ed66 docs: Fix invalid references and broken links 
This commit fixes quite a few broken links and references, minor typos,
and improves wording in some sections.
2025-02-05 22:28:26 +02:00

2514 lines
75 KiB
C
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/* GIO - GLib Input, Output and Streaming Library
*
* Copyright 2011-2018 Red Hat, Inc.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* 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 2.1 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 "gio_trace.h"
#include "gtask.h"
#include "gasyncresult.h"
#include "gcancellable.h"
#include "glib-private.h"
#include "gtrace-private.h"
#include "glibintl.h"
#include <string.h>
/**
* GTask:
*
* A `GTask` represents and manages a cancellable ‘task’.
*
* ## Asynchronous operations
*
* The most common usage of `GTask` is as a [iface@Gio.AsyncResult], to
* manage data during an asynchronous operation. You call
* [ctor@Gio.Task.new] in the ‘start’ method, followed by
* [method@Gio.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
* [method@Gio.Task.return_pointer] or [method@Gio.Task.return_error], which
* will save the value you give it and then invoke the task’s callback
* function in the thread-default main context (see
* [method@GLib.MainContext.push_thread_default])
* where it was created (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 [iface@Gio.AsyncResult]), and you can
* use [method@Gio.Task.propagate_pointer] or the like to extract the
* return value.
*
* Using `GTask` requires the thread-default [struct@GLib.MainContext] from when
* the `GTask` was constructed to be running at least until the task has
* completed and its data has been freed.
*
* If a `GTask` has been constructed and its callback set, it is an error to
* not call `g_task_return_*()` on it. GLib will warn at runtime if this happens
* (since 2.76).
*
* Here is an example for using `GTask` as a [iface@Gio.AsyncResult]:
* ```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. [method@Gio.Task.get_cancellable], [method@Gio.Task.get_context],
* and [method@Gio.Task.get_priority] allow you to get back the task’s
* [class@Gio.Cancellable], [struct@GLib.MainContext], and
* [I/O priority](iface.AsyncResult.html#io-priority)
* when starting a new subtask, so you don’t have to keep track
* of them yourself. [method@Gio.Task.attach_source] simplifies the case
* of waiting for a source to fire (automatically using the correct
* [struct@GLib.MainContext] and priority).
*
* Here is an example for chained asynchronous operations:
* ```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 (task, g_object_ref (cake), g_object_unref);
* g_object_unref (task);
* }
*
* static gboolean
* 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);
*
* return G_SOURCE_REMOVE;
* }
*
* 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, 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 [method@Gio.Task.run_in_thread] to turn a synchronous
* operation into an asynchronous one, by running it in a thread.
* When it completes, the result will be dispatched to the thread-default
* main context (see [method@GLib.MainContext.push_thread_default])
* where the `GTask` was created.
*
* Running a task in a thread:
* ```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, [method@Gio.Task.run_in_thread] and
* [method@Gio.Task.run_in_thread_sync] can be used to turn an uncancellable
* operation into a cancellable one. If you call
* [method@Gio.Task.set_return_on_cancel], passing `TRUE`, then if the task’s
* [class@Gio.Cancellable] 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:
* ```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 [class@Gio.SimpleAsyncResult]
*
* `GTask`’s API attempts to be simpler than [class@Gio.SimpleAsyncResult]’s
* in several ways:
*
* - You can save task-specific data with [method@Gio.Task.set_task_data], and
* retrieve it later with [method@Gio.Task.get_task_data]. This replaces the
* abuse of [method@Gio.SimpleAsyncResult.set_op_res_gpointer] for the same
* purpose with [class@Gio.SimpleAsyncResult].
* - In addition to the task data, `GTask` also keeps track of the
* [priority](iface.AsyncResult.html#io-priority), [class@Gio.Cancellable],
* and [struct@GLib.MainContext] 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.
* - [method@Gio.Task.return_error_if_cancelled] provides simplified
* handling for cancellation. In addition, cancellation
* overrides any other `GTask` return value by default, like
* [class@Gio.SimpleAsyncResult] does when
* [method@Gio.SimpleAsyncResult.set_check_cancellable] is called.
* (You can use [method@Gio.Task.set_check_cancellable] to turn off that
* behavior.) On the other hand, [method@Gio.Task.run_in_thread]
* guarantees that it will always run your
* `task_func`, even if the task’s [class@Gio.Cancellable]
* is already cancelled before the task gets a chance to run;
* you can start your `task_func` with a
* [method@Gio.Task.return_error_if_cancelled] check if you need the
* old behavior.
* - The ‘return’ methods (eg, [method@Gio.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 [struct@GLib.MainContext], or delayed
* until the next iteration of the current [struct@GLib.MainContext].)
* - The ‘finish’ functions for `GTask` based operations are generally
* much simpler than [class@Gio.SimpleAsyncResult] ones, normally consisting
* of only a single call to [method@Gio.Task.propagate_pointer] or the like.
* Since [method@Gio.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 [class@Gio.SimpleAsyncResult], it was common to call
* [method@Gio.SimpleAsyncResult.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
* [method@Gio.AsyncResult.legacy_propagate_error] to do old-style
* [class@Gio.SimpleAsyncResult] error-returning behavior, and
* [method@Gio.AsyncResult.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 [method@Gio.InputStream.read_async]).
*
* ## Thread-safety considerations
*
* Due to some infelicities in the API design, there is a
* thread-safety concern that users of `GTask` have to be aware of:
*
* If the `main` thread drops its last reference to the source object
* or the task data before the task is finalized, then the finalizers
* of these objects may be called on the worker thread.
*
* This is a problem if the finalizers use non-threadsafe API, and
* can lead to hard-to-debug crashes. Possible workarounds include:
*
* - Clear task data in a signal handler for `notify::completed`
* - Keep iterating a main context in the main thread and defer
* dropping the reference to the source object to that main
* context when the task is finalized
*/
struct _GTask {
GObject parent_instance;
gpointer source_object;
gpointer source_tag;
gchar *name; /* (owned); may only be modified before the #GTask is threaded */
gpointer task_data;
GDestroyNotify task_data_destroy;
GMainContext *context;
gint64 creation_time;
gint priority;
GCancellable *cancellable;
GAsyncReadyCallback callback;
gpointer callback_data;
GTaskThreadFunc task_func;
GMutex lock;
GCond cond;
/* This can’t be in the bit field because we access it from TRACE(). */
gboolean thread_cancelled;
/* Protected by the lock when task is threaded: */
guint thread_complete : 1;
guint return_on_cancel : 1;
guint : 0;
/* Unprotected, but written to when task runs in thread: */
guint completed : 1;
guint had_error : 1;
guint result_set : 1;
guint ever_returned : 1;
guint : 0;
/* Read-only once task runs in thread: */
guint check_cancellable : 1;
guint synchronous : 1;
guint blocking_other_task : 1;
guint name_is_static : 1;
GError *error;
union {
gpointer pointer;
gssize size;
gboolean boolean;
} result;
GDestroyNotify result_destroy;
};
#define G_TASK_IS_THREADED(task) ((task)->task_func != NULL)
struct _GTaskClass
{
GObjectClass parent_class;
};
typedef enum
{
PROP_COMPLETED = 1,
} GTaskProperty;
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 GSource *task_pool_manager;
static guint64 task_wait_time;
static gint tasks_running;
static guint task_pool_max_counter;
static guint tasks_running_counter;
/* When the task pool fills up and blocks, and the program keeps
* queueing more tasks, we will slowly add more threads to the pool
* (in case the existing tasks are trying to queue subtasks of their
* own) until tasks start completing again. These "overflow" threads
* will only run one task apiece, and then exit, so the pool will
* eventually get back down to its base size.
*
* The base and multiplier below gives us 10 extra threads after about
* a second of blocking, 30 after 5 seconds, 100 after a minute, and
* 200 after 20 minutes.
*
* We specify maximum pool size of 330 to increase the waiting time up
* to around 30 minutes.
*/
#define G_TASK_POOL_SIZE 10
#define G_TASK_WAIT_TIME_BASE 100000
#define G_TASK_WAIT_TIME_MULTIPLIER 1.03
#define G_TASK_WAIT_TIME_MAX_POOL_SIZE 330
static void
g_task_init (GTask *task)
{
task->check_cancellable = TRUE;
}
#ifdef G_ENABLE_DEBUG
G_LOCK_DEFINE_STATIC (task_list);
static GPtrArray *task_list = NULL;
void
g_task_print_alive_tasks (void)
{
GString *message_str = g_string_new ("");
G_LOCK (task_list);
if (task_list != NULL)
{
g_string_append_printf (message_str, "%u GTasks still alive:", task_list->len);
for (guint i = 0; i < task_list->len; i++)
{
GTask *task = g_ptr_array_index (task_list, i);
const gchar *name = g_task_get_name (task);
g_string_append_printf (message_str,
"\n • GTask %p, %s, ref count: %u, ever_returned: %u, completed: %u",
task, (name != NULL) ? name : "(no name set)",
((GObject *) task)->ref_count,
task->ever_returned, task->completed);
}
}
else
{
g_string_append (message_str, "No GTasks still alive");
}
G_UNLOCK (task_list);
g_message ("%s", message_str->str);
g_string_free (message_str, TRUE);
}
static void
g_task_constructed (GObject *object)
{
GTask *task = G_TASK (object);
G_OBJECT_CLASS (g_task_parent_class)->constructed (object);
/* Track pending tasks for debugging purposes */
G_LOCK (task_list);
if (G_UNLIKELY (task_list == NULL))
task_list = g_ptr_array_new ();
g_ptr_array_add (task_list, task);
G_UNLOCK (task_list);
}
#endif /* G_ENABLE_DEBUG */
static void
g_task_finalize (GObject *object)
{
GTask *task = G_TASK (object);
/* Warn if a #GTask is finalised without g_task_return() ever having been
* called on it.
*
* Tasks without a callback or which are run in g_task_run_in_thread{,_sync}()
* only trigger a debug message as that’s sometimes used as a pattern for
* running work in a worker thread without caring about the result. */
if (!task->ever_returned)
{
gchar *owned_task_name = NULL;
const gchar *task_name = g_task_get_name (task);
if (task_name == NULL)
task_name = owned_task_name = g_strdup_printf ("%p", task);
if (task->callback != NULL && !G_TASK_IS_THREADED (task))
g_critical ("GTask %s (source object: %p, source tag: %p) finalized without "
"ever returning (using g_task_return_*()). This potentially "
"indicates a bug in the program.",
task_name, task->source_object, task->source_tag);
else
g_debug ("GTask %s (source object: %p, source tag: %p) finalized without "
"ever returning (using g_task_return_*()). This potentially "
"indicates a bug in the program.",
task_name, task->source_object, task->source_tag);
g_free (owned_task_name);
}
g_clear_object (&task->source_object);
g_clear_object (&task->cancellable);
if (!task->name_is_static)
g_free (task->name);
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);
}
/* Track pending tasks for debugging purposes */
#ifdef G_ENABLE_DEBUG
G_LOCK (task_list);
g_assert (task_list != NULL);
g_ptr_array_remove_fast (task_list, task);
if (G_UNLIKELY (task_list->len == 0))
g_clear_pointer (&task_list, g_ptr_array_unref);
G_UNLOCK (task_list);
#endif /* G_ENABLE_DEBUG */
G_OBJECT_CLASS (g_task_parent_class)->finalize (object);
}
/**
* g_task_new:
* @source_object: (nullable) (type GObject): the #GObject that owns
* this task, or %NULL.
* @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: 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
* (see [method@GLib.MainContext.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);
TRACE (GIO_TASK_NEW (task, source_object, cancellable,
callback, callback_data));
return task;
}
/**
* g_task_report_error:
* @source_object: (nullable) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async) (closure callback_data): a #GAsyncReadyCallback.
* @callback_data: 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_set_static_name (task, G_STRFUNC);
g_task_return_error (task, error);
g_object_unref (task);
}
/**
* g_task_report_new_error:
* @source_object: (nullable) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async) (closure callback_data): a #GAsyncReadyCallback.
* @callback_data: 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: (nullable): task-specific data
* @task_data_destroy: (nullable): #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)
{
g_return_if_fail (G_IS_TASK (task));
if (task->task_data_destroy)
task->task_data_destroy (task->task_data);
task->task_data = task_data;
task->task_data_destroy = task_data_destroy;
TRACE (GIO_TASK_SET_TASK_DATA (task, task_data, task_data_destroy));
}
/**
* g_task_set_priority:
* @task: the #GTask
* @priority: the [priority](iface.AsyncResult.html#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)
{
g_return_if_fail (G_IS_TASK (task));
task->priority = priority;
TRACE (GIO_TASK_SET_PRIORITY (task, 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 (G_IS_TASK (task));
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
* uninterruptible 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 (G_IS_TASK (task), FALSE);
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.
*
* A macro wrapper around this function will automatically set the
* task’s name to the string form of @source_tag if it’s not already
* set, for convenience.
*
* Since: 2.36
*/
void
(g_task_set_source_tag) (GTask *task,
gpointer source_tag)
{
g_return_if_fail (G_IS_TASK (task));
task->source_tag = source_tag;
TRACE (GIO_TASK_SET_SOURCE_TAG (task, source_tag));
}
/**
* g_task_set_name:
* @task: a #GTask
* @name: (nullable): a human readable name for the task, or %NULL to unset it
*
* Sets @task’s name, used in debugging and profiling. The name defaults to
* %NULL.
*
* The task name should describe in a human readable way what the task does.
* For example, ‘Open file’ or ‘Connect to network host’. It is used to set the
* name of the #GSource used for idle completion of the task.
*
* This function may only be called before the @task is first used in a thread
* other than the one it was constructed in.
*
* Since: 2.60
*/
void
(g_task_set_name) (GTask *task,
const char *name)
{
char *new_name;
g_return_if_fail (G_IS_TASK (task));
new_name = g_strdup (name);
if (!task->name_is_static)
g_free (task->name);
task->name = g_steal_pointer (&new_name);
task->name_is_static = FALSE;
}
/**
* g_task_set_static_name:
* @task: a #GTask
* @name: (nullable): a human readable name for the task. Must be a string literal
*
* Sets @task’s name, used in debugging and profiling.
*
* This is a variant of g_task_set_name() that avoids copying @name.
*
* This function is called automatically by [method@Gio.Task.set_source_tag]
* unless a name is set.
*
* Since: 2.76
*/
void
g_task_set_static_name (GTask *task,
const char *name)
{
g_return_if_fail (G_IS_TASK (task));
if (!task->name_is_static)
g_free (task->name);
task->name = (char *) name;
task->name_is_static = TRUE;
}
/**
* 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) (nullable) (type GObject): @task's source object, or %NULL
*
* Since: 2.36
*/
gpointer
g_task_get_source_object (GTask *task)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
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)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
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)
{
g_return_val_if_fail (G_IS_TASK (task), G_PRIORITY_DEFAULT);
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
* (see [method@GLib.MainContext.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)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
return task->context;
}
/**
* g_task_get_cancellable:
* @task: a #GTask
*
* Gets @task's #GCancellable
*
* Returns: (nullable) (transfer none): @task's #GCancellable
*
* Since: 2.36
*/
GCancellable *
g_task_get_cancellable (GTask *task)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
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)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
/* Convert from a bit field to a boolean. */
return task->check_cancellable ? TRUE : FALSE;
}
/**
* 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)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
/* Convert from a bit field to a boolean. */
return task->return_on_cancel ? TRUE : FALSE;
}
/**
* 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)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
return task->source_tag;
}
/**
* g_task_get_name:
* @task: a #GTask
*
* Gets @task’s name. See g_task_set_name().
*
* Returns: (nullable) (transfer none): @task’s name, or %NULL
* Since: 2.60
*/
const gchar *
g_task_get_name (GTask *task)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
return task->name;
}
static void
g_task_return_now (GTask *task)
{
TRACE (GIO_TASK_BEFORE_RETURN (task, task->source_object, task->callback,
task->callback_data));
g_main_context_push_thread_default (task->context);
if (task->callback != NULL)
{
task->callback (task->source_object,
G_ASYNC_RESULT (task),
task->callback_data);
}
task->completed = TRUE;
g_object_notify (G_OBJECT (task), "completed");
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_FROM_THREAD)
task->ever_returned = TRUE;
if (type == G_TASK_RETURN_SUCCESS)
task->result_set = TRUE;
if (task->synchronous)
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)
{
/* Finally, if the task has been cancelled, we shouldn't
* return synchronously from inside the
* GCancellable::cancelled handler. It's easier to run
* another iteration of the main loop than tracking how the
* cancellation was handled.
*/
if (!g_cancellable_is_cancelled (task->cancellable))
{
g_task_return_now (task);
g_object_unref (task);
return;
}
}
}
/* Otherwise, complete in the next iteration */
source = g_idle_source_new ();
/* Note: in case the task name is NULL we set it as a const string instead
* of going through the concat path which is more expensive and may show in the
* profiler if g_task_return is called very often
*/
if (task->name == NULL)
g_source_set_static_name (source, "[gio] (unnamed) complete_in_idle_cb");
else
{
gchar *source_name;
source_name = g_strconcat ("[gio] ", task->name, " complete_in_idle_cb", NULL);
g_source_set_name (source, source_name);
g_free (source_name);
}
g_task_attach_source (task, source, 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;
}
TRACE (GIO_TASK_AFTER_RUN_IN_THREAD (task, task->thread_cancelled));
task->thread_complete = TRUE;
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 gboolean
task_pool_manager_timeout (gpointer user_data)
{
g_mutex_lock (&task_pool_mutex);
g_thread_pool_set_max_threads (task_pool, tasks_running + 1, NULL);
g_trace_set_int64_counter (task_pool_max_counter, tasks_running + 1);
g_source_set_ready_time (task_pool_manager, -1);
g_mutex_unlock (&task_pool_mutex);
return TRUE;
}
static void
g_task_thread_setup (void)
{
g_private_set (&task_private, GUINT_TO_POINTER (TRUE));
g_mutex_lock (&task_pool_mutex);
tasks_running++;
g_trace_set_int64_counter (tasks_running_counter, tasks_running);
if (tasks_running == G_TASK_POOL_SIZE)
task_wait_time = G_TASK_WAIT_TIME_BASE;
else if (tasks_running > G_TASK_POOL_SIZE && tasks_running < G_TASK_WAIT_TIME_MAX_POOL_SIZE)
task_wait_time = (guint64) (task_wait_time * G_TASK_WAIT_TIME_MULTIPLIER);
if (tasks_running >= G_TASK_POOL_SIZE)
g_source_set_ready_time (task_pool_manager, g_get_monotonic_time () + task_wait_time);
g_mutex_unlock (&task_pool_mutex);
}
static void
g_task_thread_cleanup (void)
{
gint tasks_pending;
g_mutex_lock (&task_pool_mutex);
tasks_pending = g_thread_pool_unprocessed (task_pool);
if (tasks_running > G_TASK_POOL_SIZE)
{
g_thread_pool_set_max_threads (task_pool, tasks_running - 1, NULL);
g_trace_set_int64_counter (task_pool_max_counter, tasks_running - 1);
}
else if (tasks_running + tasks_pending < G_TASK_POOL_SIZE)
g_source_set_ready_time (task_pool_manager, -1);
if (tasks_running > G_TASK_POOL_SIZE && tasks_running < G_TASK_WAIT_TIME_MAX_POOL_SIZE)
task_wait_time = (guint64) (task_wait_time / G_TASK_WAIT_TIME_MULTIPLIER);
tasks_running--;
g_trace_set_int64_counter (tasks_running_counter, tasks_running);
g_mutex_unlock (&task_pool_mutex);
g_private_set (&task_private, GUINT_TO_POINTER (FALSE));
}
static void
g_task_thread_pool_thread (gpointer thread_data,
gpointer pool_data)
{
GTask *task = thread_data;
g_task_thread_setup ();
task->task_func (task, task->source_object, task->task_data,
task->cancellable);
g_task_thread_complete (task);
g_object_unref (task);
g_task_thread_cleanup ();
}
static void
task_thread_cancelled (GCancellable *cancellable,
gpointer user_data)
{
GTask *task = user_data;
/* Move this task to the front of the queue - no need for
* a complete resorting of the queue.
*/
g_thread_pool_move_to_front (task_pool, task);
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);
TRACE (GIO_TASK_BEFORE_RUN_IN_THREAD (task, task_func));
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;
TRACE (GIO_TASK_AFTER_RUN_IN_THREAD (task, task->thread_cancelled));
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,
G_CONNECT_DEFAULT);
}
if (g_private_get (&task_private))
task->blocking_other_task = TRUE;
g_thread_pool_push (task_pool, g_object_ref (task), NULL);
}
/**
* g_task_run_in_thread:
* @task: a #GTask
* @task_func: (scope async): 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.
*
* Although GLib currently rate-limits the tasks queued via
* g_task_run_in_thread(), you should not assume that it will always
* do this. If you have a very large number of tasks to run (several tens of
* tasks), but don't want them to all run at once, you should only queue a
* limited number of them (around ten) at a time.
*
* Be aware that if your task depends on other tasks to complete, use of this
* function could lead to a livelock if the other tasks also use this function
* and enough of them (around 10) execute in a dependency chain, as that will
* exhaust the thread pool. If this situation is possible, consider using a
* separate worker thread or thread pool explicitly, rather than using
* g_task_run_in_thread().
*
* 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: (scope async): 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.
* #GTask:completed will be set to %TRUE just before this function returns.
*
* Although GLib currently rate-limits the tasks queued via
* g_task_run_in_thread_sync(), you should not assume that it will
* always do this. If you have a very large number of tasks to run,
* but don't want them to all run at once, you should only queue a
* limited number of them at a time.
*
* 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);
TRACE (GIO_TASK_BEFORE_RETURN (task, task->source_object,
NULL /* callback */,
NULL /* callback data */));
/* Notify of completion in this thread. */
task->completed = TRUE;
g_object_notify (G_OBJECT (task), "completed");
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](iface.AsyncResult.html#io-priority),
* and sets @source's callback to @callback, with @task as the callback's
* `user_data`.
*
* It will set the @source’s name to the task’s name (as set with
* g_task_set_name()), if one has been set on the task and the source doesn’t
* yet have a name.
*
* 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_return_if_fail (G_IS_TASK (task));
g_source_set_callback (source, callback,
g_object_ref (task), g_object_unref);
g_source_set_priority (source, task->priority);
if (task->name != NULL && g_source_get_name (source) == NULL)
g_source_set_name (source, task->name);
g_source_attach (source, task->context);
}
static gboolean
g_task_propagate_error (GTask *task,
GError **error)
{
gboolean error_set;
if (task->check_cancellable &&
g_cancellable_set_error_if_cancelled (task->cancellable, error))
error_set = TRUE;
else if (task->error)
{
g_propagate_error (error, task->error);
task->error = NULL;
task->had_error = TRUE;
error_set = TRUE;
}
else
error_set = FALSE;
TRACE (GIO_TASK_PROPAGATE (task, error_set));
return error_set;
}
/**
* g_task_return_pointer:
* @task: a #GTask
* @result: (nullable) (transfer full): the pointer result of a task
* function
* @result_destroy: (nullable): 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 (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
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)
{
g_return_val_if_fail (G_IS_TASK (task), NULL);
if (g_task_propagate_error (task, error))
return NULL;
g_return_val_if_fail (task->result_set, 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 (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
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)
{
g_return_val_if_fail (G_IS_TASK (task), -1);
if (g_task_propagate_error (task, error))
return -1;
g_return_val_if_fail (task->result_set, -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 (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
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)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
if (g_task_propagate_error (task, error))
return FALSE;
g_return_val_if_fail (task->result_set, 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 [method@Gio.Task.return_new_error],
* [method@Gio.Task.return_new_error_literal].
*
* Since: 2.36
*/
void
g_task_return_error (GTask *task,
GError *error)
{
g_return_if_fail (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
g_return_if_fail (error != NULL);
task->error = error;
g_task_return (task, G_TASK_RETURN_ERROR);
}
/**
* g_task_return_prefixed_error:
* @task: a #GTask.
* @error: (transfer full): the #GError result of a task function.
* @format: a string with format characters.
* @...: a list of values to insert into @format.
*
* Sets @task's result to @error (which @task assumes ownership of), with
* the message prefixed according to @format, 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_prefixed_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_error(), g_prefix_error().
*
* Since: 2.80
*/
void
g_task_return_prefixed_error (GTask *task,
GError *error,
const char *format,
...)
{
char *prefix;
va_list ap;
g_return_if_fail (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
g_return_if_fail (error != NULL);
task->error = error;
va_start (ap, format);
prefix = g_strdup_vprintf (format, ap);
va_end (ap);
g_prefix_error_literal (&task->error, prefix);
g_free (prefix);
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_new_error_literal:
* @task: a #GTask.
* @domain: a #GQuark.
* @code: an error code.
* @message: an error message
*
* Sets @task’s result to a new [type@GLib.Error] created from @domain, @code,
* @message and completes the task.
*
* See [method@Gio.Task.return_pointer] for more discussion of exactly what
* ‘completing the task’ means.
*
* See also [method@Gio.Task.return_new_error].
*
* Since: 2.80
*/
void
g_task_return_new_error_literal (GTask *task,
GQuark domain,
gint code,
const char *message)
{
g_task_return_error (task, g_error_new_literal (domain, code, message));
}
/**
* 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 (G_IS_TASK (task), FALSE);
g_return_val_if_fail (!task->ever_returned, 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)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
if (task->error != NULL || task->had_error)
return TRUE;
if (task->check_cancellable && g_cancellable_is_cancelled (task->cancellable))
return TRUE;
return FALSE;
}
static void
value_free (gpointer value)
{
g_value_unset (value);
g_free (value);
}
/**
* g_task_return_value:
* @task: a #GTask
* @result: (nullable) (transfer none): the #GValue result of
* a task function
*
* Sets @task's result to @result (by copying it) and completes the task.
*
* If @result is %NULL then a #GValue of type %G_TYPE_POINTER
* with a value of %NULL will be used for the result.
*
* This is a very generic low-level method intended primarily for use
* by language bindings; for C code, g_task_return_pointer() and the
* like will normally be much easier to use.
*
* Since: 2.64
*/
void
g_task_return_value (GTask *task,
GValue *result)
{
GValue *value;
g_return_if_fail (G_IS_TASK (task));
g_return_if_fail (!task->ever_returned);
value = g_new0 (GValue, 1);
if (result == NULL)
{
g_value_init (value, G_TYPE_POINTER);
g_value_set_pointer (value, NULL);
}
else
{
g_value_init (value, G_VALUE_TYPE (result));
g_value_copy (result, value);
}
g_task_return_pointer (task, value, value_free);
}
/**
* g_task_propagate_value:
* @task: a #GTask
* @value: (out caller-allocates): return location for the #GValue
* @error: return location for a #GError
*
* Gets the result of @task as a #GValue, and transfers ownership of
* that value to the caller. As with g_task_return_value(), this is
* a generic low-level method; g_task_propagate_pointer() and the like
* will usually be more useful for C code.
*
* If the task resulted in an error, or was cancelled, then this will
* instead set @error and return %FALSE.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: %TRUE if @task succeeded, %FALSE on error.
*
* Since: 2.64
*/
gboolean
g_task_propagate_value (GTask *task,
GValue *value,
GError **error)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
g_return_val_if_fail (value != NULL, FALSE);
g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
if (g_task_propagate_error (task, error))
return FALSE;
g_return_val_if_fail (task->result_set, FALSE);
g_return_val_if_fail (task->result_destroy == value_free, FALSE);
memcpy (value, task->result.pointer, sizeof (GValue));
g_free (task->result.pointer);
task->result_destroy = NULL;
task->result_set = FALSE;
return TRUE;
}
/**
* g_task_get_completed:
* @task: a #GTask.
*
* Gets the value of #GTask:completed. This changes from %FALSE to %TRUE after
* the task’s callback is invoked, and will return %FALSE if called from inside
* the callback.
*
* Returns: %TRUE if the task has completed, %FALSE otherwise.
*
* Since: 2.44
*/
gboolean
g_task_get_completed (GTask *task)
{
g_return_val_if_fail (G_IS_TASK (task), FALSE);
/* Convert from a bit field to a boolean. */
return task->completed ? TRUE : FALSE;
}
/**
* g_task_is_valid:
* @result: (type Gio.AsyncResult): A #GAsyncResult
* @source_object: (nullable) (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 gboolean
trivial_source_dispatch (GSource *source,
GSourceFunc callback,
gpointer user_data)
{
return callback (user_data);
}
GSourceFuncs trivial_source_funcs = {
NULL, /* prepare */
NULL, /* check */
trivial_source_dispatch,
NULL, /* finalize */
NULL, /* closure */
NULL /* marshal */
};
static void
g_task_thread_pool_init (void)
{
task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
G_TASK_POOL_SIZE, FALSE, NULL);
g_assert (task_pool != NULL);
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
task_pool_manager = g_source_new (&trivial_source_funcs, sizeof (GSource));
g_source_set_static_name (task_pool_manager, "GTask thread pool manager");
g_source_set_callback (task_pool_manager, task_pool_manager_timeout, NULL, NULL);
g_source_set_ready_time (task_pool_manager, -1);
g_source_attach (task_pool_manager,
GLIB_PRIVATE_CALL (g_get_worker_context ()));
g_source_unref (task_pool_manager);
}
static void
g_task_get_property (GObject *object,
guint prop_id,
GValue *value,
GParamSpec *pspec)
{
GTask *task = G_TASK (object);
switch ((GTaskProperty) prop_id)
{
case PROP_COMPLETED:
g_value_set_boolean (value, g_task_get_completed (task));
break;
}
}
static void
g_task_class_init (GTaskClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
#ifdef G_ENABLE_DEBUG
gobject_class->constructed = g_task_constructed;
#endif
gobject_class->get_property = g_task_get_property;
gobject_class->finalize = g_task_finalize;
/**
* GTask:completed:
*
* Whether the task has completed, meaning its callback (if set) has been
* invoked.
*
* This can only happen after g_task_return_pointer(),
* g_task_return_error() or one of the other return functions have been called
* on the task. However, it is not guaranteed to happen immediately after
* those functions are called, as the task’s callback may need to be scheduled
* to run in a different thread.
*
* That means it is **not safe** to use this property to track whether a
* return function has been called on the #GTask. Callers must do that
* tracking themselves, typically by linking the lifetime of the #GTask to the
* control flow of their code.
*
* This property is guaranteed to change from %FALSE to %TRUE exactly once.
*
* The #GObject::notify signal for this change is emitted in the same main
* context as the task’s callback, immediately after that callback is invoked.
*
* Since: 2.44
*/
g_object_class_install_property (gobject_class, PROP_COMPLETED,
g_param_spec_boolean ("completed", NULL, NULL,
FALSE, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
if (G_UNLIKELY (task_pool_max_counter == 0))
{
/* We use two counters to track characteristics of the GTask thread pool.
* task pool max size - the value of g_thread_pool_set_max_threads()
* tasks running - the number of running threads
*/
task_pool_max_counter = g_trace_define_int64_counter ("GIO", "task pool max size", "Maximum number of threads allowed in the GTask thread pool; see g_thread_pool_set_max_threads()");
tasks_running_counter = g_trace_define_int64_counter ("GIO", "tasks running", "Number of currently running tasks in the GTask thread pool");
}
}
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;
}
Reference in New Issue View Git Blame Copy Permalink