From 57bde3c9bda9cfdf1e55fd6ddc1c354bde1ee654 Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@endlessos.org>
Date: Mon, 30 May 2022 17:54:18 +0100
Subject: [PATCH] glocalfilemonitor: Skip event handling if the source has been
destroyed
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
This should prevent unbounded growth of the `event_queue` in the
unlikely case that the `GSource` is removed from its `GMainContext` and
destroyed separately from the `GFileMonitor`.
I’m not sure if that can currently happen, but it could with future
refactoring, so it’s best to address the possibility now while we’re
thinking about this bit of code.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #1941
---
gio/glocalfilemonitor.c | 29 +++++++++++++++++++++++------
1 file changed, 23 insertions(+), 6 deletions(-)
diff --git a/gio/glocalfilemonitor.c b/gio/glocalfilemonitor.c
index f408d0707..68afd7b51 100644
--- a/gio/glocalfilemonitor.c
+++ b/gio/glocalfilemonitor.c
@@ -358,11 +358,28 @@ g_file_monitor_source_handle_event (GFileMonitorSource *fms,
g_mutex_lock (&fms->lock);
- /* NOTE: We process events even if the file monitor has already been disposed.
- * The reason is that we must not take a reference to the instance here
- * as destroying it from the event handling thread will lead to a
- * deadlock when taking the lock in _ih_sub_cancel.
+ /* NOTE:
+ *
+ * We process events even if the file monitor has already been disposed.
+ * The reason is that we must not take a reference to the instance here as
+ * destroying it from the event handling thread will lead to a deadlock when
+ * taking the lock in _ih_sub_cancel.
+ *
+ * This results in seemingly-unbounded growth of the `event_queue` with the
+ * calls to `g_file_monitor_source_queue_event()`. However, each of those sets
+ * the ready time on the #GSource, which means that it will be dispatched in
+ * a subsequent iteration of the #GMainContext it’s attached to. At that
+ * point, `g_file_monitor_source_dispatch()` will return %FALSE, and this will
+ * trigger finalisation of the source. That will clear the `event_queue`.
+ *
+ * If the source is no longer attached, this will return early to prevent
+ * unbounded queueing.
*/
+ if (g_source_is_destroyed ((GSource *) fms))
+ {
+ g_mutex_unlock (&fms->lock);
+ return TRUE;
+ }
switch (event_type)
{
@@ -595,9 +612,9 @@ g_file_monitor_source_dispose (GFileMonitorSource *fms)
g_file_monitor_source_update_ready_time (fms);
- g_mutex_unlock (&fms->lock);
-
g_source_destroy ((GSource *) fms);
+
+ g_mutex_unlock (&fms->lock);
}
static void