[glib/glib-2-72: 3/4] tests: Add a test for GFileMonitor deadlocks

[Simon McVittie <smcv src gnome org>]

commit 1fc6a5c9b6a2b620ac4370d64c558f9b33aff063
Author: Philip Withnall <pwithnall endlessos org>
Date:   Mon May 30 17:55:43 2022 +0100

    tests: Add a test for GFileMonitor deadlocks
    
    This test is opportunistic in that it’s not possible to detect whether
    the race condition has been hit (other than by hitting a deadlock).
    
    So the only approach we can take for testing is to loop over the code
    which has previously been known to cause a deadlock a number of times.
    
    The number of repetitions is chosen from running the test with the
    deadlock fix reverted.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>
    
    Helps: #1941

 gio/tests/testfilemonitor.c | 52 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
---
diff --git a/gio/tests/testfilemonitor.c b/gio/tests/testfilemonitor.c
index a47aeab386..082f0db26f 100644
--- a/gio/tests/testfilemonitor.c
+++ b/gio/tests/testfilemonitor.c
@@ -1036,6 +1036,57 @@ test_file_hard_links (Fixture       *fixture,
   g_object_unref (data.output_stream);
 }
 
+static void
+test_finalize_in_callback (Fixture       *fixture,
+                           gconstpointer  user_data)
+{
+  GFile *file = NULL;
+  guint i;
+
+  g_test_summary ("Test that finalization of a GFileMonitor in one of its "
+                  "callbacks doesn’t cause a deadlock.");
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/1941";);
+
+  file = g_file_get_child (fixture->tmp_dir, "race-file");
+
+  for (i = 0; i < 50; i++)
+    {
+      GFileMonitor *monitor = NULL;
+      GError *local_error = NULL;
+
+      /* Monitor the file. */
+      monitor = g_file_monitor_file (file, G_FILE_MONITOR_NONE, NULL, &local_error);
+      g_assert_no_error (local_error);
+      g_assert_nonnull (monitor);
+
+      /* Create the file. */
+      g_file_replace_contents (file, "hello", 5, NULL, FALSE,
+                               G_FILE_CREATE_NONE, NULL, NULL, &local_error);
+      g_assert_no_error (local_error);
+
+      /* Immediately drop the last ref to the monitor in the hope that this
+       * happens in the middle of the critical section in
+       * g_file_monitor_source_handle_event(), so that any cleanup at the end
+       * of that function is done with a now-finalised file monitor. */
+      g_object_unref (monitor);
+
+      /* Re-create the monitor and do the same again for deleting the file, to
+       * give a second chance at hitting the race condition. */
+      monitor = g_file_monitor_file (file, G_FILE_MONITOR_NONE, NULL, &local_error);
+      g_assert_no_error (local_error);
+      g_assert_nonnull (monitor);
+
+      /* Delete the file. */
+      g_file_delete (file, NULL, &local_error);
+      g_assert_no_error (local_error);
+
+      /* Drop the ref again. */
+      g_object_unref (monitor);
+    }
+
+  g_object_unref (file);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -1047,6 +1098,7 @@ main (int argc, char *argv[])
   g_test_add ("/monitor/dir-not-existent", Fixture, NULL, setup, test_dir_non_existent, teardown);
   g_test_add ("/monitor/cross-dir-moves", Fixture, NULL, setup, test_cross_dir_moves, teardown);
   g_test_add ("/monitor/file/hard-links", Fixture, NULL, setup, test_file_hard_links, teardown);
+  g_test_add ("/monitor/finalize-in-callback", Fixture, NULL, setup, test_finalize_in_callback, teardown);
 
   return g_test_run ();
 }