[gimp] app: in gimp-parallel, cancel ongoing async operations upon exit

[Ell <ell src gnome org>]

commit e46fdc714e8c88b42e12d0a637f1da688b4e7e9a
Author: Ell <ell_se yahoo com>
Date:   Mon Oct 1 05:13:45 2018 -0400

    app: in gimp-parallel, cancel ongoing async operations upon exit
    
    When shutting-down gimp-parallel, cancel and/or abort any ongoing
    and queued async operations, instead of finishing them (async
    operations that already started executing will be canceled, but
    execution will be blocked until they're finished.)  This is
    especially important since we're shutting down gimp-parallel before
    the destruction of data factories.  This commit causes any ongoing
    async operations of the factories to be canceled on shutdown,
    rather than waiting for them to finish normally.

 app/core/gimp-parallel.cc | 55 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 45 insertions(+), 10 deletions(-)
---
diff --git a/app/core/gimp-parallel.cc b/app/core/gimp-parallel.cc
index 5ebad358ff..bad87b2292 100644
--- a/app/core/gimp-parallel.cc
+++ b/app/core/gimp-parallel.cc
@@ -42,6 +42,7 @@ extern "C"
 #include "gimp.h"
 #include "gimp-parallel.h"
 #include "gimpasync.h"
+#include "gimpcancelable.h"
 
 
 #define GIMP_PARALLEL_MAX_THREADS            64
@@ -60,9 +61,11 @@ typedef struct
 
 typedef struct
 {
-  GThread  *thread;
+  GThread   *thread;
 
-  gboolean  quit;
+  gboolean   quit;
+
+  GimpAsync *current_async;
 } GimpParallelRunAsyncThread;
 
 typedef struct
@@ -89,9 +92,11 @@ typedef struct
 
 static void       gimp_parallel_notify_num_processors    (GimpGeglConfig               *config);
 
-static void       gimp_parallel_set_n_threads            (gint                          n_threads);
+static void       gimp_parallel_set_n_threads            (gint                          n_threads,
+                                                          gboolean                      finish_tasks);
 
-static void       gimp_parallel_run_async_set_n_threads  (gint                          n_threads);
+static void       gimp_parallel_run_async_set_n_threads  (gint                          n_threads,
+                                                          gboolean                      finish_tasks);
 static gpointer   gimp_parallel_run_async_thread_func    (GimpParallelRunAsyncThread   *thread);
 static void       gimp_parallel_run_async_execute_task   (GimpParallelRunAsyncTask     *task);
 static void       gimp_parallel_run_async_cancel         (GimpAsync                    *async);
@@ -147,7 +152,7 @@ gimp_parallel_exit (Gimp *gimp)
                                         NULL);
 
   /* stop all threads */
-  gimp_parallel_set_n_threads (0);
+  gimp_parallel_set_n_threads (0, /* finish_tasks = */ FALSE);
 }
 
 GimpAsync *
@@ -441,18 +446,21 @@ gimp_parallel_distribute_area (const GeglRectangle            *area,
 static void
 gimp_parallel_notify_num_processors (GimpGeglConfig *config)
 {
-  gimp_parallel_set_n_threads (config->num_processors);
+  gimp_parallel_set_n_threads (config->num_processors,
+                               /* finish_tasks = */ TRUE);
 }
 
 static void
-gimp_parallel_set_n_threads (gint n_threads)
+gimp_parallel_set_n_threads (gint     n_threads,
+                             gboolean finish_tasks)
 {
-  gimp_parallel_run_async_set_n_threads (n_threads);
+  gimp_parallel_run_async_set_n_threads (n_threads, finish_tasks);
   gimp_parallel_distribute_set_n_threads (n_threads);
 }
 
 static void
-gimp_parallel_run_async_set_n_threads (gint n_threads)
+gimp_parallel_run_async_set_n_threads (gint     n_threads,
+                                       gboolean finish_tasks)
 {
   gint i;
 
@@ -483,6 +491,9 @@ gimp_parallel_run_async_set_n_threads (gint n_threads)
             &gimp_parallel_run_async_threads[i];
 
           thread->quit = TRUE;
+
+          if (thread->current_async && ! finish_tasks)
+            gimp_cancelable_cancel (GIMP_CANCELABLE (thread->current_async));
         }
 
       g_cond_broadcast (&gimp_parallel_run_async_cond);
@@ -511,7 +522,21 @@ gimp_parallel_run_async_set_n_threads (gint n_threads)
           g_object_set_data (G_OBJECT (task->async),
                              "gimp-parallel-run-async-link", NULL);
 
-          gimp_parallel_run_async_execute_task (task);
+          if (finish_tasks)
+            {
+              gimp_parallel_run_async_execute_task (task);
+            }
+          else
+            {
+              if (task->user_data && task->user_data_destroy_func)
+                task->user_data_destroy_func (task->user_data);
+
+              gimp_async_abort (task->async);
+
+              g_object_unref (task->async);
+
+              g_slice_free (GimpParallelRunAsyncTask, task);
+            }
         }
     }
 }
@@ -533,11 +558,15 @@ gimp_parallel_run_async_thread_func (GimpParallelRunAsyncThread *thread)
           g_object_set_data (G_OBJECT (task->async),
                              "gimp-parallel-run-async-link", NULL);
 
+          thread->current_async = GIMP_ASYNC (g_object_ref (task->async));
+
           g_mutex_unlock (&gimp_parallel_run_async_mutex);
 
           gimp_parallel_run_async_execute_task (task);
 
           g_mutex_lock (&gimp_parallel_run_async_mutex);
+
+          g_clear_object (&thread->current_async);
         }
 
       if (thread->quit)
@@ -571,6 +600,12 @@ gimp_parallel_run_async_cancel (GimpAsync *async)
   GList                    *link;
   GimpParallelRunAsyncTask *task = NULL;
 
+  link = (GList *) g_object_get_data (G_OBJECT (async),
+                                      "gimp-parallel-run-async-link");
+
+  if (! link)
+    return;
+
   g_mutex_lock (&gimp_parallel_run_async_mutex);
 
   link = (GList *) g_object_get_data (G_OBJECT (async),