mirror of
https://gitlab.gnome.org/GNOME/glib.git
synced 2024-12-25 15:06:14 +01:00
gthreadedresolver: Switch to using a separate thread pool
Rather than running lookups in the global shared thread pool belonging to `GTask`, run them in a private thread pool. This is needed because the global shared thread pool is constrained to only 14 threads. If there are 14 ongoing calls to `g_task_run_in_thread()` from any library/code in the process, and then one of them asks to do a DNS lookup, the lookup will block forever. Under certain circumstances, particularly where there are a couple of deep chains of dependent tasks running with `g_task_run_in_thread()`, this can livelock the program. Since `GResolver` is likely to be called as a frequent leaf call in certain workloads, and in particular there are likely to be several lookups requested at the same time, it makes sense to move resolver lookups to a private thread pool. Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This commit is contained in:
Philip Withnall
parent
84074ce757
commit
7b18e6205a
@ -41,18 +41,39 @@
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struct _GThreadedResolver
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{
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GResolver parent_instance;
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GThreadPool *thread_pool; /* (owned) */
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};
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G_DEFINE_TYPE (GThreadedResolver, g_threaded_resolver, G_TYPE_RESOLVER)
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static void threaded_resolver_worker_cb (GTask *task,
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gpointer source_object,
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gpointer task_data,
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GCancellable *cancellable);
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static void run_task_in_thread_pool_async (GThreadedResolver *self,
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GTask *task);
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static void run_task_in_thread_pool_sync (GThreadedResolver *self,
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GTask *task);
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static void threaded_resolver_worker_cb (gpointer task_data,
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gpointer user_data);
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static void
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g_threaded_resolver_init (GThreadedResolver *gtr)
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g_threaded_resolver_init (GThreadedResolver *self)
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{
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self->thread_pool = g_thread_pool_new_full (threaded_resolver_worker_cb,
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self,
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(GDestroyNotify) g_object_unref,
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20,
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FALSE,
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NULL);
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}
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static void
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g_threaded_resolver_finalize (GObject *object)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (object);
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g_thread_pool_free (self->thread_pool, TRUE, FALSE);
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self->thread_pool = NULL;
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G_OBJECT_CLASS (g_threaded_resolver_parent_class)->finalize (object);
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}
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static GResolverError
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@ -95,6 +116,23 @@ typedef struct {
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GResolverRecordType record_type;
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} lookup_records;
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};
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GCond cond; /* used for signalling completion of the task when running it sync */
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GMutex lock;
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/* This enum indicates that a particular code path has claimed the
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* task and is shortly about to call g_task_return_*() on it.
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* This must be accessed with GThreadedResolver.lock held. */
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enum
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{
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NOT_YET,
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COMPLETED, /* libc lookup call has completed successfully or errored */
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} will_return;
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/* Whether the thread pool thread executing this lookup has finished executing
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* it and g_task_return_*() has been called on it already.
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* This must be accessed with GThreadedResolver.lock held. */
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gboolean has_returned;
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} LookupData;
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static LookupData *
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@ -103,6 +141,8 @@ lookup_data_new_by_name (const char *hostname,
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{
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LookupData *data = g_new0 (LookupData, 1);
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data->lookup_type = LOOKUP_BY_NAME;
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g_cond_init (&data->cond);
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g_mutex_init (&data->lock);
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data->lookup_by_name.hostname = g_strdup (hostname);
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data->lookup_by_name.address_family = address_family;
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return g_steal_pointer (&data);
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@ -113,6 +153,8 @@ lookup_data_new_by_address (GInetAddress *address)
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{
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LookupData *data = g_new0 (LookupData, 1);
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data->lookup_type = LOOKUP_BY_ADDRESS;
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g_cond_init (&data->cond);
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g_mutex_init (&data->lock);
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data->lookup_by_address.address = g_object_ref (address);
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return g_steal_pointer (&data);
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}
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@ -123,6 +165,8 @@ lookup_data_new_records (const gchar *rrname,
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{
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LookupData *data = g_new0 (LookupData, 1);
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data->lookup_type = LOOKUP_RECORDS;
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g_cond_init (&data->cond);
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g_mutex_init (&data->lock);
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data->lookup_records.rrname = g_strdup (rrname);
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data->lookup_records.record_type = record_type;
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return g_steal_pointer (&data);
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@ -145,6 +189,9 @@ lookup_data_free (LookupData *data)
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g_assert_not_reached ();
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}
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g_mutex_clear (&data->lock);
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g_cond_clear (&data->cond);
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g_free (data);
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}
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@ -243,6 +290,7 @@ lookup_by_name (GResolver *resolver,
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GCancellable *cancellable,
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GError **error)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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GTask *task;
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GList *addresses;
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LookupData *data;
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@ -252,8 +300,9 @@ lookup_by_name (GResolver *resolver,
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g_task_set_source_tag (task, lookup_by_name);
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g_task_set_name (task, "[gio] resolver lookup");
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread_sync (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_sync (self, task);
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addresses = g_task_propagate_pointer (task, error);
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g_object_unref (task);
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@ -285,6 +334,7 @@ lookup_by_name_with_flags (GResolver *resolver,
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GCancellable *cancellable,
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GError **error)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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GTask *task;
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GList *addresses;
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LookupData *data;
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@ -294,8 +344,9 @@ lookup_by_name_with_flags (GResolver *resolver,
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g_task_set_source_tag (task, lookup_by_name_with_flags);
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g_task_set_name (task, "[gio] resolver lookup");
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread_sync (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_sync (self, task);
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addresses = g_task_propagate_pointer (task, error);
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g_object_unref (task);
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@ -310,6 +361,7 @@ lookup_by_name_with_flags_async (GResolver *resolver,
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GAsyncReadyCallback callback,
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gpointer user_data)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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GTask *task;
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LookupData *data;
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@ -322,8 +374,9 @@ lookup_by_name_with_flags_async (GResolver *resolver,
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g_task_set_source_tag (task, lookup_by_name_with_flags_async);
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g_task_set_name (task, "[gio] resolver lookup");
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_async (self, task);
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g_object_unref (task);
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}
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@ -415,6 +468,7 @@ lookup_by_address (GResolver *resolver,
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GCancellable *cancellable,
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GError **error)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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LookupData *data = NULL;
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GTask *task;
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gchar *name;
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@ -424,8 +478,9 @@ lookup_by_address (GResolver *resolver,
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g_task_set_source_tag (task, lookup_by_address);
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g_task_set_name (task, "[gio] resolver lookup");
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread_sync (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_sync (self, task);
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name = g_task_propagate_pointer (task, error);
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g_object_unref (task);
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@ -439,6 +494,7 @@ lookup_by_address_async (GResolver *resolver,
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GAsyncReadyCallback callback,
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gpointer user_data)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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LookupData *data = NULL;
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GTask *task;
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@ -447,8 +503,9 @@ lookup_by_address_async (GResolver *resolver,
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g_task_set_source_tag (task, lookup_by_address_async);
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g_task_set_name (task, "[gio] resolver lookup");
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_async (self, task);
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g_object_unref (task);
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}
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@ -1247,6 +1304,7 @@ lookup_records (GResolver *resolver,
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GCancellable *cancellable,
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GError **error)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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GTask *task;
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GList *records;
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LookupData *data = NULL;
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@ -1258,8 +1316,8 @@ lookup_records (GResolver *resolver,
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data = lookup_data_new_records (rrname, record_type);
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread_sync (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_sync (self, task);
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records = g_task_propagate_pointer (task, error);
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g_object_unref (task);
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@ -1274,6 +1332,7 @@ lookup_records_async (GResolver *resolver,
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GAsyncReadyCallback callback,
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gpointer user_data)
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{
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GThreadedResolver *self = G_THREADED_RESOLVER (resolver);
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GTask *task;
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LookupData *data = NULL;
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@ -1284,8 +1343,8 @@ lookup_records_async (GResolver *resolver,
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data = lookup_data_new_records (rrname, record_type);
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g_task_set_task_data (task, g_steal_pointer (&data), (GDestroyNotify) lookup_data_free);
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g_task_set_return_on_cancel (task, TRUE);
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g_task_run_in_thread (task, threaded_resolver_worker_cb);
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run_task_in_thread_pool_async (self, task);
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g_object_unref (task);
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}
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@ -1300,13 +1359,41 @@ lookup_records_finish (GResolver *resolver,
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}
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static void
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threaded_resolver_worker_cb (GTask *task,
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gpointer source_object,
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gpointer task_data,
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GCancellable *cancellable)
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run_task_in_thread_pool_async (GThreadedResolver *self,
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GTask *task)
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{
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LookupData *data = task_data;
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LookupData *data = g_task_get_task_data (task);
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g_mutex_lock (&data->lock);
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g_thread_pool_push (self->thread_pool, g_object_ref (task), NULL);
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g_mutex_unlock (&data->lock);
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}
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static void
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run_task_in_thread_pool_sync (GThreadedResolver *self,
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GTask *task)
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{
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LookupData *data = g_task_get_task_data (task);
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run_task_in_thread_pool_async (self, task);
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g_mutex_lock (&data->lock);
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while (!data->has_returned)
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g_cond_wait (&data->cond, &data->lock);
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g_mutex_unlock (&data->lock);
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}
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static void
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threaded_resolver_worker_cb (gpointer task_data,
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gpointer user_data)
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{
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GTask *task = G_TASK (g_steal_pointer (&task_data));
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LookupData *data = g_task_get_task_data (task);
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GCancellable *cancellable = g_task_get_cancellable (task);
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GError *local_error = NULL;
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gboolean should_return;
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switch (data->lookup_type) {
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case LOOKUP_BY_NAME:
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@ -1316,10 +1403,19 @@ threaded_resolver_worker_cb (GTask *task,
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cancellable,
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&local_error);
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if (addresses != NULL)
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g_task_return_pointer (task, g_steal_pointer (&addresses), (GDestroyNotify) g_resolver_free_addresses);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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g_mutex_lock (&data->lock);
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should_return = g_atomic_int_compare_and_exchange (&data->will_return, NOT_YET, COMPLETED);
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g_mutex_unlock (&data->lock);
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if (should_return)
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{
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if (addresses != NULL)
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g_task_return_pointer (task, g_steal_pointer (&addresses), (GDestroyNotify) g_resolver_free_addresses);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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}
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g_clear_pointer (&addresses, g_resolver_free_addresses);
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}
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break;
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case LOOKUP_BY_ADDRESS:
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@ -1328,10 +1424,19 @@ threaded_resolver_worker_cb (GTask *task,
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cancellable,
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&local_error);
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if (name != NULL)
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g_task_return_pointer (task, g_steal_pointer (&name), g_free);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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g_mutex_lock (&data->lock);
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should_return = g_atomic_int_compare_and_exchange (&data->will_return, NOT_YET, COMPLETED);
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g_mutex_unlock (&data->lock);
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if (should_return)
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{
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if (name != NULL)
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g_task_return_pointer (task, g_steal_pointer (&name), g_free);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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}
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g_clear_pointer (&name, g_free);
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}
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break;
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case LOOKUP_RECORDS:
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@ -1341,22 +1446,43 @@ threaded_resolver_worker_cb (GTask *task,
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cancellable,
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&local_error);
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if (records != NULL)
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g_task_return_pointer (task, g_steal_pointer (&records), (GDestroyNotify) free_records);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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g_mutex_lock (&data->lock);
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should_return = g_atomic_int_compare_and_exchange (&data->will_return, NOT_YET, COMPLETED);
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g_mutex_unlock (&data->lock);
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if (should_return)
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{
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if (records != NULL)
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g_task_return_pointer (task, g_steal_pointer (&records), (GDestroyNotify) free_records);
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else
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g_task_return_error (task, g_steal_pointer (&local_error));
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}
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g_clear_pointer (&records, free_records);
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}
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break;
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default:
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g_assert_not_reached ();
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}
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/* Signal completion of a task. */
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g_mutex_lock (&data->lock);
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g_assert (!data->has_returned);
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data->has_returned = TRUE;
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g_cond_broadcast (&data->cond);
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g_mutex_unlock (&data->lock);
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g_object_unref (task);
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}
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static void
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g_threaded_resolver_class_init (GThreadedResolverClass *threaded_class)
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{
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GObjectClass *object_class = G_OBJECT_CLASS (threaded_class);
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GResolverClass *resolver_class = G_RESOLVER_CLASS (threaded_class);
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object_class->finalize = g_threaded_resolver_finalize;
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resolver_class->lookup_by_name = lookup_by_name;
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resolver_class->lookup_by_name_async = lookup_by_name_async;
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resolver_class->lookup_by_name_finish = lookup_by_name_finish;
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