From ee5d5b9a8c4d3bd77c86aacc4b4a15210051e399 Mon Sep 17 00:00:00 2001
From: Willy-JL <49810075+Willy-JL@users.noreply.github.com>
Date: Sun, 10 Sep 2023 03:07:10 +0200
Subject: [PATCH] Fix view_port_update() apps random deadlocks

---
 applications/services/gui/view_port.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/applications/services/gui/view_port.c b/applications/services/gui/view_port.c
index 6723a777bb..7b6644d306 100644
--- a/applications/services/gui/view_port.c
+++ b/applications/services/gui/view_port.c
@@ -174,9 +174,23 @@ void view_port_input_callback_set(
 
 void view_port_update(ViewPort* view_port) {
     furi_assert(view_port);
-    furi_check(furi_mutex_acquire(view_port->mutex, FuriWaitForever) == FuriStatusOk);
+    // view_port_update() does not modify viewport memory
+    // nor does it need time sensitive data in order to work
+    // but when used in apps in a input loop it can cause deadlocks with draw() being called by other means
+    // example:
+    // - app selector keeps loading animation in background, keeps drawing
+    // - because of this gui starts draw and locks viewport mutex, not in app render callback yet
+    // - app gets input, locks app mutex
+    // - app input handler calls view_port_update() which needs viewport mutex
+    // - viewport mutex already locked by draw previously
+    // - but app mutex locked by input so draw cannot complete
+    // - DEADLOCK => mutex removed from view_port_update()
+    // this is just one example, there may be many more edge cases
+    // point is, this view_port_update() has no need at all for mutex
+    // dont copy paste mutex into all functions to close jira tasks please :)
+    // furi_check(furi_mutex_acquire(view_port->mutex, FuriWaitForever) == FuriStatusOk);
     if(view_port->gui && view_port->is_enabled) gui_update(view_port->gui);
-    furi_check(furi_mutex_release(view_port->mutex) == FuriStatusOk);
+    // furi_check(furi_mutex_release(view_port->mutex) == FuriStatusOk);
 }
 
 void view_port_gui_set(ViewPort* view_port, Gui* gui) {