From 77ab8962e32fe92701407f890756cc56e47156fa Mon Sep 17 00:00:00 2001
From: Vaxry <vaxry@vaxry.net>
Date: Sat, 19 Jul 2025 16:47:14 +0200
Subject: [PATCH] eventloop: improve timer handling to avoid crashes

ref #11062
---
 src/managers/eventLoop/EventLoopManager.cpp | 22 +++++++++++++++++----
 src/managers/eventLoop/EventLoopManager.hpp |  6 ++++--
 src/managers/eventLoop/EventLoopTimer.cpp   |  4 ++--
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/managers/eventLoop/EventLoopManager.cpp b/src/managers/eventLoop/EventLoopManager.cpp
index 0389e7b86..b9ac7242e 100644
--- a/src/managers/eventLoop/EventLoopManager.cpp
+++ b/src/managers/eventLoop/EventLoopManager.cpp
@@ -102,25 +102,25 @@ void CEventLoopManager::enterLoop() {
 void CEventLoopManager::onTimerFire() {
     const auto CPY = m_timers.timers;
     for (auto const& t : CPY) {
-        if (t.strongRef() > 1 /* if it's 1, it was lost. Don't call it. */ && t->passed() && !t->cancelled())
+        if (t.strongRef() > 2 /* if it's 2, it was lost. Don't call it. */ && t->passed() && !t->cancelled())
             t->call(t);
     }
 
-    nudgeTimers();
+    scheduleRecalc();
 }
 
 void CEventLoopManager::addTimer(SP<CEventLoopTimer> timer) {
     if (std::ranges::contains(m_timers.timers, timer))
         return;
     m_timers.timers.emplace_back(timer);
-    nudgeTimers();
+    scheduleRecalc();
 }
 
 void CEventLoopManager::removeTimer(SP<CEventLoopTimer> timer) {
     if (!std::ranges::contains(m_timers.timers, timer))
         return;
     std::erase_if(m_timers.timers, [timer](const auto& t) { return timer == t; });
-    nudgeTimers();
+    scheduleRecalc();
 }
 
 static void timespecAddNs(timespec* pTimespec, int64_t delta) {
@@ -136,7 +136,21 @@ static void timespecAddNs(timespec* pTimespec, int64_t delta) {
     }
 }
 
+void CEventLoopManager::scheduleRecalc() {
+    // do not do it instantly, do it later. Avoid recursive access to the timer
+    // vector, it could be catastrophic if we modify it while iterating
+
+    if (m_timers.recalcScheduled)
+        return;
+
+    m_timers.recalcScheduled = true;
+
+    doLater([this] { nudgeTimers(); });
+}
+
 void CEventLoopManager::nudgeTimers() {
+    m_timers.recalcScheduled = false;
+
     // remove timers that have gone missing
     std::erase_if(m_timers.timers, [](const auto& t) { return t.strongRef() <= 1; });
 
diff --git a/src/managers/eventLoop/EventLoopManager.hpp b/src/managers/eventLoop/EventLoopManager.hpp
index 0835b242f..d3a67ae57 100644
--- a/src/managers/eventLoop/EventLoopManager.hpp
+++ b/src/managers/eventLoop/EventLoopManager.hpp
@@ -27,8 +27,8 @@ class CEventLoopManager {
 
     void onTimerFire();
 
-    // recalculates timers
-    void nudgeTimers();
+    // schedules a recalc of the timers
+    void scheduleRecalc();
 
     // schedules a function to run later, aka in a wayland idle event.
     void doLater(const std::function<void()>& fn);
@@ -69,6 +69,7 @@ class CEventLoopManager {
   private:
     // Manages the event sources after AQ pollFDs change.
     void syncPollFDs();
+    void nudgeTimers();
 
     struct SEventSourceData {
         SP<Aquamarine::SPollFD> pollFD;
@@ -84,6 +85,7 @@ class CEventLoopManager {
     struct {
         std::vector<SP<CEventLoopTimer>> timers;
         Hyprutils::OS::CFileDescriptor   timerfd;
+        bool                             recalcScheduled = false;
     } m_timers;
 
     SIdleData                        m_idle;
diff --git a/src/managers/eventLoop/EventLoopTimer.cpp b/src/managers/eventLoop/EventLoopTimer.cpp
index d4633b0d8..fa86c861a 100644
--- a/src/managers/eventLoop/EventLoopTimer.cpp
+++ b/src/managers/eventLoop/EventLoopTimer.cpp
@@ -14,13 +14,13 @@ CEventLoopTimer::CEventLoopTimer(std::optional<Time::steady_dur> timeout, std::f
 void CEventLoopTimer::updateTimeout(std::optional<Time::steady_dur> timeout) {
     if (!timeout.has_value()) {
         m_expires.reset();
-        g_pEventLoopManager->nudgeTimers();
+        g_pEventLoopManager->scheduleRecalc();
         return;
     }
 
     m_expires = Time::steadyNow() + *timeout;
 
-    g_pEventLoopManager->nudgeTimers();
+    g_pEventLoopManager->scheduleRecalc();
 }
 
 bool CEventLoopTimer::passed() {