From 010627c13ed31d9d3d0ad94be244a70616264d82 Mon Sep 17 00:00:00 2001
From: JD Smith <93749+jdtsmith@users.noreply.github.com>
Date: Sat, 25 Oct 2025 07:43:42 -0400
Subject: [PATCH] Fix GCD deadlock on sync queue draw

* src/macappkit.m (set_global_focus_view_frame): set identifier key on
drawing queue for easy identification.
(mac_draw_queue_sync): Do not dispatch empty block if already running
from drawing queue.
---
 src/macappkit.m | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/macappkit.m b/src/macappkit.m
index 40c55710363..6b678ff5a37 100644
--- a/src/macappkit.m
+++ b/src/macappkit.m
@@ -7630,6 +7630,7 @@ - (NSCandidateListTouchBarItem *)candidateListTouchBarItem
 static bool saved_focus_view_modified_p;
 #if DRAWING_USE_GCD
 static dispatch_queue_t global_focus_drawing_queue;
+static const void * kDrawingQueueKey = &kDrawingQueueKey;
 #endif
 
 static void
@@ -7651,8 +7652,12 @@ - (NSCandidateListTouchBarItem *)candidateListTouchBarItem
   if (mac_drawing_use_gcd)
     {
       if (global_focus_drawing_queue == NULL)
-	global_focus_drawing_queue =
-	  dispatch_queue_create ("org.gnu.Emacs.drawing", NULL);
+        {
+          global_focus_drawing_queue =
+            dispatch_queue_create ("org.gnu.Emacs.drawing", NULL);
+          dispatch_queue_set_specific(global_focus_drawing_queue, kDrawingQueueKey,
+                                      (void *)kDrawingQueueKey, NULL);
+        }
     }
   else
     {
@@ -7671,8 +7676,10 @@ - (NSCandidateListTouchBarItem *)candidateListTouchBarItem
 mac_draw_queue_sync (void)
 {
 #if DRAWING_USE_GCD
-  if (global_focus_drawing_queue)
-    dispatch_sync (global_focus_drawing_queue, ^{});
+  if (global_focus_drawing_queue &&
+      /* Avoid deadlock if already on the drawing queue */
+      !dispatch_get_specific(kDrawingQueueKey))
+      dispatch_sync (global_focus_drawing_queue, ^{});
 #endif
 }