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glocalfilemonitor: Keep a weak ref to the monitor in GFileMonitorSource

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Previously we were keeping a pointer to the `GFileMonitor` in a
`GFileMonitorSource` instance, but since we weren’t keeping a strong
reference, that `GFileMonitor` instance could be finalised from another
thread at any point while the source was referring to it. Not good.

Use a weak reference, and upgrade it to a strong reference whenever the
`GFileMonitorSource` is referring to the file monitor.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Helps: #1903
This commit is contained in:
Philip Withnall 2019-10-11 22:22:46 +01:00
parent 5b07fc98e0
commit 592a13b483
1 changed files with 35 additions and 28 deletions
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63
gio/glocalfilemonitor.c
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@ -46,7 +46,7 @@ struct _GFileMonitorSource {
GSource source;
GMutex lock;
gpointer instance;
GWeakRef instance_ref;
GFileMonitorFlags flags;
gchar *dirname;
gchar *basename;
@ -348,6 +348,7 @@ g_file_monitor_source_handle_event (GFileMonitorSource *fms,
gint64 event_time)
{
gboolean interesting = TRUE;
GFileMonitor *instance = NULL;
g_assert (!child || is_basename (child));
g_assert (!rename_to || is_basename (rename_to));
@ -359,7 +360,8 @@ g_file_monitor_source_handle_event (GFileMonitorSource *fms,
g_mutex_lock (&fms->lock);
/* monitor is already gone -- don't bother */
if (!fms->instance)
instance = g_weak_ref_get (&fms->instance_ref);
if (instance == NULL)
{
g_mutex_unlock (&fms->lock);
return TRUE;
@ -450,6 +452,7 @@ g_file_monitor_source_handle_event (GFileMonitorSource *fms,
g_file_monitor_source_update_ready_time (fms);
g_mutex_unlock (&fms->lock);
g_clear_object (&instance);
return interesting;
}
@ -500,9 +503,11 @@ g_file_monitor_source_dispatch (GSource *source,
QueuedEvent *event;
GQueue event_queue;
gint64 now;
GFileMonitor *instance = NULL;
/* make sure the monitor still exists */
if (!fms->instance)
instance = g_weak_ref_get (&fms->instance_ref);
if (instance == NULL)
return FALSE;
now = g_source_get_time (source);
@ -550,15 +555,18 @@ g_file_monitor_source_dispatch (GSource *source,
g_file_monitor_source_update_ready_time (fms);
g_clear_object (&instance);
g_mutex_unlock (&fms->lock);
/* We now have our list of events to deliver */
while ((event = g_queue_pop_head (&event_queue)))
{
/* an event handler could destroy 'instance', so check each time */
if (fms->instance)
g_file_monitor_emit_event (fms->instance, event->child, event->other, event->event_type);
instance = g_weak_ref_get (&fms->instance_ref);
if (instance != NULL)
g_file_monitor_emit_event (instance, event->child, event->other, event->event_type);
g_clear_object (&instance);
queued_event_free (event);
}
@ -568,32 +576,29 @@ g_file_monitor_source_dispatch (GSource *source,
static void
g_file_monitor_source_dispose (GFileMonitorSource *fms)
{
GHashTableIter iter;
gpointer seqiter;
QueuedEvent *event;
g_mutex_lock (&fms->lock);
if (fms->instance)
g_hash_table_iter_init (&iter, fms->pending_changes_table);
while (g_hash_table_iter_next (&iter, NULL, &seqiter))
{
GHashTableIter iter;
gpointer seqiter;
QueuedEvent *event;
g_hash_table_iter_init (&iter, fms->pending_changes_table);
while (g_hash_table_iter_next (&iter, NULL, &seqiter))
{
g_hash_table_iter_remove (&iter);
g_sequence_remove (seqiter);
}
while ((event = g_queue_pop_head (&fms->event_queue)))
queued_event_free (event);
g_assert (g_sequence_is_empty (fms->pending_changes));
g_assert (g_hash_table_size (fms->pending_changes_table) == 0);
g_assert (fms->event_queue.length == 0);
fms->instance = NULL;
g_file_monitor_source_update_ready_time (fms);
g_hash_table_iter_remove (&iter);
g_sequence_remove (seqiter);
}
while ((event = g_queue_pop_head (&fms->event_queue)))
queued_event_free (event);
g_assert (g_sequence_is_empty (fms->pending_changes));
g_assert (g_hash_table_size (fms->pending_changes_table) == 0);
g_assert (fms->event_queue.length == 0);
g_weak_ref_set (&fms->instance_ref, NULL);
g_file_monitor_source_update_ready_time (fms);
g_mutex_unlock (&fms->lock);
g_source_destroy ((GSource *) fms);
@ -605,7 +610,9 @@ g_file_monitor_source_finalize (GSource *source)
GFileMonitorSource *fms = (GFileMonitorSource *) source;
/* should already have been cleared in dispose of the monitor */
g_assert (fms->instance == NULL);
g_assert (g_weak_ref_get (&fms->instance_ref) == NULL);
g_weak_ref_clear (&fms->instance_ref);
g_assert (g_sequence_is_empty (fms->pending_changes));
g_assert (g_hash_table_size (fms->pending_changes_table) == 0);
g_assert (fms->event_queue.length == 0);
@ -653,7 +660,7 @@ g_file_monitor_source_new (gpointer instance,
g_source_set_name (source, "GFileMonitorSource");
g_mutex_init (&fms->lock);
fms->instance = instance;
g_weak_ref_init (&fms->instance_ref, instance);
fms->pending_changes = g_sequence_new (pending_change_free);
fms->pending_changes_table = g_hash_table_new (str_hash0, str_equal0);
fms->rate_limit = DEFAULT_RATE_LIMIT;