[evolution-data-server/gnome-3-16] Do not use GTask for CamelSession thread jobs

[Milan Crha <mcrha src gnome org>]

commit 4b85c8d57461b313aa82becdb04464eab6b3f319
Author: Milan Crha <mcrha redhat com>
Date:   Fri Apr 3 09:08:02 2015 +0200

    Do not use GTask for CamelSession thread jobs
    
    The GTask thread pool is limited (currently holds up to 10 threads)
    and it's shared by all async operations, either directly or indirectly,
    which can mean that the asynchronous operations can block session
    thread jobs, eventually invoked by the user in UI.

 camel/camel-session.c |   75 ++++++++++++++++++++++++-------------------------
 1 files changed, 37 insertions(+), 38 deletions(-)
---
diff --git a/camel/camel-session.c b/camel/camel-session.c
index ed63596..b59a39f 100644
--- a/camel/camel-session.c
+++ b/camel/camel-session.c
@@ -94,6 +94,8 @@ struct _JobData {
        CamelSessionCallback callback;
        gpointer user_data;
        GDestroyNotify notify;
+       GMainContext *main_context;
+       GError *error;
 };
 
 enum {
@@ -154,6 +156,10 @@ job_data_free (JobData *job_data)
 
        g_object_unref (job_data->session);
        g_object_unref (job_data->cancellable);
+       g_clear_error (&job_data->error);
+
+       if (job_data->main_context)
+               g_main_context_unref (job_data->main_context);
 
        if (job_data->notify != NULL)
                job_data->notify (job_data->user_data);
@@ -161,74 +167,65 @@ job_data_free (JobData *job_data)
        g_slice_free (JobData, job_data);
 }
 
-static void
-session_finish_job_cb (GObject *source_object,
-                       GAsyncResult *result,
-                       gpointer unused)
+static gboolean
+session_finish_job_cb (gpointer user_data)
 {
-       GCancellable *cancellable;
-       GError *local_error = NULL;
+       JobData *job_data = (JobData *) user_data;
 
-       cancellable = g_task_get_cancellable (G_TASK (result));
-
-       /* XXX Ignore the return value, this is just
-        *     to extract the GError if there is one. */
-       g_task_propagate_boolean (G_TASK (result), &local_error);
+       g_return_val_if_fail (job_data != NULL, FALSE);
 
        g_signal_emit (
-               CAMEL_SESSION (source_object),
+               job_data->session,
                signals[JOB_FINISHED], 0,
-               cancellable, local_error);
+               job_data->cancellable, job_data->error);
 
-       g_clear_error (&local_error);
+       return FALSE;
 }
 
 static void
-session_do_job_cb (GTask *task,
-                   gpointer source_object,
-                   gpointer task_data,
-                   GCancellable *cancellable)
+session_job_thread (gpointer data,
+                   gpointer user_data)
 {
-       JobData *job_data;
-       GError *local_error = NULL;
+       JobData *job_data = (JobData *) data;
+       GSource *source;
 
-       job_data = (JobData *) task_data;
+       g_return_if_fail (job_data != NULL);
 
        job_data->callback (
-               CAMEL_SESSION (source_object),
-               cancellable,
+               job_data->session,
+               job_data->cancellable,
                job_data->user_data,
-               &local_error);
+               &job_data->error);
 
-       if (local_error != NULL) {
-               g_task_return_error (task, local_error);
-       } else {
-               g_task_return_boolean (task, TRUE);
-       }
+       source = g_idle_source_new ();
+       g_source_set_priority (source, G_PRIORITY_DEFAULT);
+       g_source_set_callback (source, session_finish_job_cb, job_data, (GDestroyNotify) job_data_free);
+       g_source_attach (source, job_data->main_context);
+       g_source_unref (source);
 }
 
 static gboolean
 session_start_job_cb (gpointer user_data)
 {
+       static GThreadPool *job_pool = NULL;
+       static GMutex job_pool_mutex;
        JobData *job_data = user_data;
-       GTask *task;
 
        g_signal_emit (
                job_data->session,
                signals[JOB_STARTED], 0,
                job_data->cancellable);
 
-       task = g_task_new (
-               job_data->session,
-               job_data->cancellable,
-               session_finish_job_cb, NULL);
+       g_mutex_lock (&job_pool_mutex);
 
-       g_task_set_task_data (
-               task, job_data, (GDestroyNotify) job_data_free);
+       if (!job_pool)
+               job_pool = g_thread_pool_new (session_job_thread, NULL, 20, FALSE, NULL);
 
-       g_task_run_in_thread (task, session_do_job_cb);
+       job_data->main_context = g_main_context_ref_thread_default ();
 
-       g_object_unref (task);
+       g_thread_pool_push (job_pool, job_data, NULL);
+
+       g_mutex_unlock (&job_pool_mutex);
 
        return FALSE;
 }
@@ -1453,6 +1450,8 @@ camel_session_submit_job (CamelSession *session,
        job_data->callback = callback;
        job_data->user_data = user_data;
        job_data->notify = notify;
+       job_data->main_context = NULL;
+       job_data->error = NULL;
 
        camel_operation_push_message (job_data->cancellable, "%s", description);