From 4ca715d2ef2615186ebe013fd30dcc15a8d0adc0 Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Fri, 5 Apr 2024 16:00:14 +0200
Subject: [PATCH] LibWeb: Skip SHTQ processing if ongoing task form queue is
 not finished

Fixes a bug when session history traversal queue task could be
interrupted by another SHTQ task execution. For example:
1. SHTQ timer callback starts executing a task from the queue.
2. spin_until() is invoked during task execution.
3. SHTQ timer callback starts executing a task from the queue.
---
 .../Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h   | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Userland/Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h b/Userland/Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h
index 88dace3641e..e54b0893ba4 100644
--- a/Userland/Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h
+++ b/Userland/Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h
@@ -25,9 +25,15 @@ public:
     SessionHistoryTraversalQueue()
     {
         m_timer = Core::Timer::create_single_shot(0, [this] {
+            if (m_is_task_running && m_queue.size() > 0) {
+                m_timer->start();
+                return;
+            }
             while (m_queue.size() > 0) {
+                m_is_task_running = true;
                 auto entry = m_queue.take_first();
                 entry.steps();
+                m_is_task_running = false;
             }
         }).release_value_but_fixme_should_propagate_errors();
     }
@@ -60,6 +66,7 @@ public:
 private:
     Vector<SessionHistoryTraversalQueueEntry> m_queue;
     RefPtr<Core::Timer> m_timer;
+    bool m_is_task_running { false };
 };
 
 }