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Merge branch 'gsource-dispose' into 'master'

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Implement a dispose function for GSource

See merge request GNOME/glib!1175
This commit is contained in:
Sebastian Dröge 2019-12-03 12:37:22 +00:00
commit 96a0f3777c
4 changed files with 225 additions and 32 deletions
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34
gio/gcancellable.c
View File

@ -642,20 +642,19 @@ typedef struct {
GSource source;
GCancellable *cancellable;
guint cancelled_handler;
gulong cancelled_handler;
} GCancellableSource;
/*
* We can't guarantee that the source still has references, so we are
* relying on the fact that g_source_set_ready_time() no longer makes
* assertions about the reference count - the source might be in the
* window between last-unref and finalize, during which its refcount
* is officially 0. However, we *can* guarantee that it's OK to
* dereference it in a limited way, because we know we haven't yet reached
* cancellable_source_finalize() - if we had, then we would have waited
* for signal emission to finish, then disconnected the signal handler
* under the lock.
* See https://bugzilla.gnome.org/show_bug.cgi?id=791754
* The reference count of the GSource might be 0 at this point but it is not
* finalized yet and its dispose function did not run yet, or otherwise we
* would have disconnected the signal handler already and due to the signal
* emission lock it would be impossible to call the signal handler at that
* point. That is: at this point we either have a fully valid GSource, or
* it's not disposed or finalized yet and we can still resurrect it as needed.
*
* As such we first ensure that we have a strong reference to the GSource in
* here before calling any other GSource API.
*/
static void
cancellable_source_cancelled (GCancellable *cancellable,
@ -663,7 +662,9 @@ cancellable_source_cancelled (GCancellable *cancellable,
{
GSource *source = user_data;
g_source_ref (source);
g_source_set_ready_time (source, 0);
g_source_unref (source);
}
static gboolean
@ -679,15 +680,15 @@ cancellable_source_dispatch (GSource *source,
}
static void
cancellable_source_finalize (GSource *source)
cancellable_source_dispose (GSource *source)
{
GCancellableSource *cancellable_source = (GCancellableSource *)source;
if (cancellable_source->cancellable)
{
g_cancellable_disconnect (cancellable_source->cancellable,
cancellable_source->cancelled_handler);
g_object_unref (cancellable_source->cancellable);
g_clear_signal_handler (&cancellable_source->cancelled_handler,
cancellable_source->cancellable);
g_clear_object (&cancellable_source->cancellable);
}
}
@ -720,7 +721,7 @@ static GSourceFuncs cancellable_source_funcs =
NULL,
NULL,
cancellable_source_dispatch,
cancellable_source_finalize,
NULL,
(GSourceFunc)cancellable_source_closure_callback,
};
@ -750,6 +751,7 @@ g_cancellable_source_new (GCancellable *cancellable)
source = g_source_new (&cancellable_source_funcs, sizeof (GCancellableSource));
g_source_set_name (source, "GCancellable");
g_source_set_dispose_function (source, cancellable_source_dispose);
cancellable_source = (GCancellableSource *)source;
if (cancellable)

111
glib/gmain.c
View File

@ -361,6 +361,8 @@ struct _GSourcePrivate
* let it remain empty on Windows) to avoid #ifdef all over the place.
*/
GSList *fds;
GSourceDisposeFunc dispose;
};
typedef struct _GSourceIter
@ -926,6 +928,40 @@ g_source_new (GSourceFuncs *source_funcs,
return source;
}
/**
* g_source_set_dispose_function:
* @source: A #GSource to set the dispose function on
* @dispose: #GSourceDisposeFunc to set on the source
*
* Set @dispose as dispose function on @source. @dispose will be called once
* the reference count of @source reaches 0 but before any of the state of the
* source is freed, especially before the finalize function is called.
*
* This means that at this point @source is still a valid #GSource and it is
* allow for the reference count to increase again until @dispose returns.
*
* The dispose function can be used to clear any "weak" references to the
* @source in other data structures in a thread-safe way where it is possible
* for another thread to increase the reference count of @source again while
* it is being freed.
*
* The finalize function can not be used for this purpose as at that point
* @source is already partially freed and not valid anymore.
*
* This should only ever be called from #GSource implementations.
*
* Since: 2.64
**/
void
g_source_set_dispose_function (GSource *source,
GSourceDisposeFunc dispose)
{
g_return_if_fail (source != NULL);
g_return_if_fail (source->priv->dispose == NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
source->priv->dispose = dispose;
}
/* Holds context's lock */
static void
g_source_iter_init (GSourceIter *iter,
@ -1185,6 +1221,8 @@ g_source_attach (GSource *source,
{
guint result = 0;
g_return_val_if_fail (source != NULL, 0);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, 0);
g_return_val_if_fail (source->context == NULL, 0);
g_return_val_if_fail (!SOURCE_DESTROYED (source), 0);
@ -1282,6 +1320,7 @@ g_source_destroy (GSource *source)
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
context = source->context;
@ -1313,6 +1352,7 @@ g_source_get_id (GSource *source)
guint result;
g_return_val_if_fail (source != NULL, 0);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, 0);
g_return_val_if_fail (source->context != NULL, 0);
LOCK_CONTEXT (source->context);
@ -1342,6 +1382,8 @@ g_source_get_id (GSource *source)
GMainContext *
g_source_get_context (GSource *source)
{
g_return_val_if_fail (source != NULL, NULL);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, NULL);
g_return_val_if_fail (source->context != NULL || !SOURCE_DESTROYED (source), NULL);
return source->context;
@ -1373,6 +1415,7 @@ g_source_add_poll (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (fd != NULL);
g_return_if_fail (!SOURCE_DESTROYED (source));
@ -1409,6 +1452,7 @@ g_source_remove_poll (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (fd != NULL);
g_return_if_fail (!SOURCE_DESTROYED (source));
@ -1459,7 +1503,9 @@ g_source_add_child_source (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (child_source != NULL);
g_return_if_fail (g_atomic_int_get (&child_source->ref_count) > 0);
g_return_if_fail (!SOURCE_DESTROYED (source));
g_return_if_fail (!SOURCE_DESTROYED (child_source));
g_return_if_fail (child_source->context == NULL);
@ -1520,7 +1566,9 @@ g_source_remove_child_source (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (child_source != NULL);
g_return_if_fail (g_atomic_int_get (&child_source->ref_count) > 0);
g_return_if_fail (child_source->priv->parent_source == source);
g_return_if_fail (!SOURCE_DESTROYED (source));
g_return_if_fail (!SOURCE_DESTROYED (child_source));
@ -1603,6 +1651,7 @@ g_source_set_callback_indirect (GSource *source,
GSourceCallbackFuncs *old_cb_funcs;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (callback_funcs != NULL || callback_data == NULL);
context = source->context;
@ -1665,6 +1714,7 @@ g_source_set_callback (GSource *source,
GSourceCallback *new_callback;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
TRACE (GLIB_SOURCE_SET_CALLBACK (source, func, data, notify));
@ -1778,6 +1828,7 @@ g_source_set_priority (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (source->priv->parent_source == NULL);
context = source->context;
@ -1801,6 +1852,7 @@ gint
g_source_get_priority (GSource *source)
{
g_return_val_if_fail (source != NULL, 0);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, 0);
return source->priority;
}
@ -1843,15 +1895,7 @@ g_source_set_ready_time (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
/* We deliberately don't check for ref_count > 0 here, because that
* breaks cancellable_source_cancelled() in GCancellable: it has no
* way to find out that the last-unref has happened until the
* finalize() function is called, but that's too late, because the
* ref_count already has already reached 0 before that time.
* However, priv is only poisoned (set to NULL) after finalize(),
* so we can use this as a simple guard against use-after-free.
* See https://bugzilla.gnome.org/show_bug.cgi?id=791754 */
g_return_if_fail (source->priv != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
context = source->context;
@ -1895,6 +1939,7 @@ gint64
g_source_get_ready_time (GSource *source)
{
g_return_val_if_fail (source != NULL, -1);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, -1);
return source->priv->ready_time;
}
@ -1916,6 +1961,7 @@ g_source_set_can_recurse (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
context = source->context;
@ -1944,6 +1990,7 @@ gboolean
g_source_get_can_recurse (GSource *source)
{
g_return_val_if_fail (source != NULL, FALSE);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, FALSE);
return (source->flags & G_SOURCE_CAN_RECURSE) != 0;
}
@ -1980,6 +2027,7 @@ g_source_set_name (GSource *source,
GMainContext *context;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
context = source->context;
@ -2015,6 +2063,7 @@ const char *
g_source_get_name (GSource *source)
{
g_return_val_if_fail (source != NULL, NULL);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, NULL);
return source->name;
}
@ -2071,6 +2120,9 @@ GSource *
g_source_ref (GSource *source)
{
g_return_val_if_fail (source != NULL, NULL);
/* We allow ref_count == 0 here to allow the dispose function to resurrect
* the GSource if needed */
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) >= 0, NULL);
g_atomic_int_inc (&source->ref_count);
@ -2094,6 +2146,28 @@ g_source_unref_internal (GSource *source,
if (g_atomic_int_dec_and_test (&source->ref_count))
{
/* If there's a dispose function, call this first */
if (source->priv->dispose)
{
/* Temporarily increase the ref count again so that GSource methods
* can be called from dispose(). */
g_atomic_int_inc (&source->ref_count);
if (context)
UNLOCK_CONTEXT (context);
source->priv->dispose (source);
if (context)
LOCK_CONTEXT (context);
/* Now the reference count might be bigger than 0 again, in which
* case we simply return from here before freeing the source */
if (!g_atomic_int_dec_and_test (&source->ref_count))
{
if (!have_lock && context)
UNLOCK_CONTEXT (context);
return;
}
}
TRACE (GLIB_SOURCE_BEFORE_FREE (source, context,
source->source_funcs->finalize));
@ -2114,6 +2188,8 @@ g_source_unref_internal (GSource *source,
if (source->source_funcs->finalize)
{
gint old_ref_count;
/* Temporarily increase the ref count again so that GSource methods
* can be called from finalize(). */
g_atomic_int_inc (&source->ref_count);
@ -2122,11 +2198,14 @@ g_source_unref_internal (GSource *source,
source->source_funcs->finalize (source);
if (context)
LOCK_CONTEXT (context);
g_atomic_int_add (&source->ref_count, -1);
old_ref_count = g_atomic_int_add (&source->ref_count, -1);
g_warn_if_fail (old_ref_count == 1);
}
if (old_cb_funcs)
{
gint old_ref_count;
/* Temporarily increase the ref count again so that GSource methods
* can be called from callback_funcs.unref(). */
g_atomic_int_inc (&source->ref_count);
@ -2137,7 +2216,8 @@ g_source_unref_internal (GSource *source,
if (context)
LOCK_CONTEXT (context);
g_atomic_int_add (&source->ref_count, -1);
old_ref_count = g_atomic_int_add (&source->ref_count, -1);
g_warn_if_fail (old_ref_count == 1);
}
g_free (source->name);
@ -2181,6 +2261,7 @@ void
g_source_unref (GSource *source)
{
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_source_unref_internal (source, source->context, FALSE);
}
@ -2484,6 +2565,7 @@ g_source_add_unix_fd (GSource *source,
GPollFD *poll_fd;
g_return_val_if_fail (source != NULL, NULL);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, NULL);
g_return_val_if_fail (!SOURCE_DESTROYED (source), NULL);
poll_fd = g_new (GPollFD, 1);
@ -2537,6 +2619,7 @@ g_source_modify_unix_fd (GSource *source,
GPollFD *poll_fd;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (g_slist_find (source->priv->fds, tag));
context = source->context;
@ -2574,6 +2657,7 @@ g_source_remove_unix_fd (GSource *source,
GPollFD *poll_fd;
g_return_if_fail (source != NULL);
g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);
g_return_if_fail (g_slist_find (source->priv->fds, tag));
context = source->context;
@ -2622,6 +2706,7 @@ g_source_query_unix_fd (GSource *source,
GPollFD *poll_fd;
g_return_val_if_fail (source != NULL, 0);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, 0);
g_return_val_if_fail (g_slist_find (source->priv->fds, tag), 0);
poll_fd = tag;
@ -3052,6 +3137,8 @@ g_main_current_source (void)
gboolean
g_source_is_destroyed (GSource *source)
{
g_return_val_if_fail (source != NULL, TRUE);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, TRUE);
return SOURCE_DESTROYED (source);
}
@ -4452,6 +4539,8 @@ g_source_get_time (GSource *source)
GMainContext *context;
gint64 result;
g_return_val_if_fail (source != NULL, 0);
g_return_val_if_fail (g_atomic_int_get (&source->ref_count) > 0, 0);
g_return_val_if_fail (source->context != NULL, 0);
context = source->context;

21
glib/gmain.h
View File

@ -204,6 +204,20 @@ typedef gboolean (*GSourceFunc) (gpointer user_data);
typedef void (*GChildWatchFunc) (GPid pid,
gint status,
gpointer user_data);
/**
* GSourceDisposeFunc:
* @source: #GSource that is currently being disposed
*
* Dispose function for @source. See g_source_set_dispose_function() for
* details.
*
* Since: 2.64
*/
GLIB_AVAILABLE_TYPE_IN_2_64
typedef void (*GSourceDisposeFunc) (GSource *source);
struct _GSource
{
/*< private >*/
@ -536,6 +550,13 @@ GMainContext *g_main_loop_get_context (GMainLoop *loop);
GLIB_AVAILABLE_IN_ALL
GSource *g_source_new (GSourceFuncs *source_funcs,
guint struct_size);
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
GLIB_AVAILABLE_IN_2_64
void g_source_set_dispose_function (GSource *source,
GSourceDisposeFunc dispose);
G_GNUC_END_IGNORE_DEPRECATIONS
GLIB_AVAILABLE_IN_ALL
GSource *g_source_ref (GSource *source);
GLIB_AVAILABLE_IN_ALL

91
glib/tests/mainloop.c
View File

@ -25,25 +25,29 @@
#include <stdio.h>
#include <string.h>
static gboolean cb (gpointer data)
static gboolean
cb (gpointer data)
{
return FALSE;
}
static gboolean prepare (GSource *source, gint *time)
static gboolean
prepare (GSource *source, gint *time)
{
return FALSE;
}
static gboolean check (GSource *source)
static gboolean
check (GSource *source)
{
return FALSE;
}
static gboolean dispatch (GSource *source, GSourceFunc cb, gpointer date)
static gboolean
dispatch (GSource *source, GSourceFunc cb, gpointer date)
{
return FALSE;
}
GSourceFuncs funcs = {
static GSourceFuncs funcs = {
prepare,
check,
dispatch,
@ -1746,6 +1750,82 @@ test_nfds (void)
g_main_context_unref (ctx);
}
static gboolean source_finalize_called = FALSE;
static guint source_dispose_called = 0;
static gboolean source_dispose_recycle = FALSE;
static void
finalize (GSource *source)
{
g_assert_false (source_finalize_called);
source_finalize_called = TRUE;
}
static void
dispose (GSource *source)
{
/* Dispose must always be called before finalize */
g_assert_false (source_finalize_called);
if (source_dispose_recycle)
g_source_ref (source);
source_dispose_called++;
}
static GSourceFuncs source_funcs = {
prepare,
check,
dispatch,
finalize
};
static void
test_maincontext_source_finalization (void)
{
GSource *source;
/* Check if GSource destruction without dispose function works and calls the
* finalize function as expected */
source_finalize_called = FALSE;
source_dispose_called = 0;
source_dispose_recycle = FALSE;
source = g_source_new (&source_funcs, sizeof (GSource));
g_source_unref (source);
g_assert_cmpint (source_dispose_called, ==, 0);
g_assert_true (source_finalize_called);
/* Check if GSource destruction with dispose function works and calls the
* dispose and finalize function as expected */
source_finalize_called = FALSE;
source_dispose_called = 0;
source_dispose_recycle = FALSE;
source = g_source_new (&source_funcs, sizeof (GSource));
g_source_set_dispose_function (source, dispose);
g_source_unref (source);
g_assert_cmpint (source_dispose_called, ==, 1);
g_assert_true (source_finalize_called);
/* Check if GSource destruction with dispose function works and recycling
* the source from dispose works without calling the finalize function */
source_finalize_called = FALSE;
source_dispose_called = 0;
source_dispose_recycle = TRUE;
source = g_source_new (&source_funcs, sizeof (GSource));
g_source_set_dispose_function (source, dispose);
g_source_unref (source);
g_assert_cmpint (source_dispose_called, ==, 1);
g_assert_false (source_finalize_called);
/* Check if the source is properly recycled */
g_assert_cmpint (source->ref_count, ==, 1);
/* And then get rid of it properly */
source_dispose_recycle = FALSE;
g_source_unref (source);
g_assert_cmpint (source_dispose_called, ==, 2);
g_assert_true (source_finalize_called);
}
int
main (int argc, char *argv[])
{
@ -1753,6 +1833,7 @@ main (int argc, char *argv[])
g_test_bug_base ("http://bugzilla.gnome.org/");
g_test_add_func ("/maincontext/basic", test_maincontext_basic);
g_test_add_func ("/maincontext/source_finalization", test_maincontext_source_finalization);
g_test_add_func ("/mainloop/basic", test_mainloop_basic);
g_test_add_func ("/mainloop/timeouts", test_timeouts);
g_test_add_func ("/mainloop/priorities", test_priorities);