From 8cb235bf19b15d84b034028935f230b7f0ee4801 Mon Sep 17 00:00:00 2001
From: Christian Speckner <christian.speckner@mayflower.de>
Date: Mon, 17 Dec 2018 00:30:42 +0100
Subject: [PATCH] Hack around race condition in timers.

---
 .vscode/settings.json          | 3 ++-
 src/common/StaggeredLogger.cxx | 9 ++++++---
 src/common/StaggeredLogger.hxx | 7 ++++++-
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/.vscode/settings.json b/.vscode/settings.json
index c00ccb459..9108568ea 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -67,6 +67,7 @@
         "unordered_map": "cpp",
         "istream": "cpp",
         "thread": "cpp",
-        "utility": "cpp"
+        "utility": "cpp",
+        "streambuf": "cpp"
     }
 }
diff --git a/src/common/StaggeredLogger.cxx b/src/common/StaggeredLogger.cxx
index 71b341007..112c48d43 100644
--- a/src/common/StaggeredLogger.cxx
+++ b/src/common/StaggeredLogger.cxx
@@ -43,7 +43,8 @@ StaggeredLogger::StaggeredLogger(const string& message, Logger logger)
     myMaxIntervalFactor(9),
     myCurrentIntervalFactor(1),
     myCooldownTime(1000),
-    myTimer(new TimerManager())
+    myTimer(new TimerManager()),
+    myTimerCallbackId(0)
 {
   if (logger) myLogger = logger;
 }
@@ -148,14 +149,16 @@ void StaggeredLogger::startInterval()
   myLastIntervalStartTimestamp = now;
 
   myTimer->clear(myTimerId);
-  myTimerId = myTimer->setTimeout(std::bind(&StaggeredLogger::onTimerExpired, this), myCurrentIntervalSize);
+  myTimerId = myTimer->setTimeout(std::bind(&StaggeredLogger::onTimerExpired, this, ++myTimerCallbackId), myCurrentIntervalSize);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void StaggeredLogger::onTimerExpired()
+void StaggeredLogger::onTimerExpired(uInt32 timerCallbackId)
 {
   std::lock_guard<std::mutex> lock(myMutex);
 
+  if (timerCallbackId != myTimerCallbackId) return;
+
   logLine();
 
   myIsCurrentlyCollecting = false;
diff --git a/src/common/StaggeredLogger.hxx b/src/common/StaggeredLogger.hxx
index 6e6e93c06..8bcffcb9a 100644
--- a/src/common/StaggeredLogger.hxx
+++ b/src/common/StaggeredLogger.hxx
@@ -52,7 +52,7 @@ class StaggeredLogger {
 
     void _setLogger(Logger logger);
 
-    void onTimerExpired();
+    void onTimerExpired(uInt32 timerId);
 
     void startInterval();
 
@@ -83,6 +83,11 @@ class StaggeredLogger {
     // our destructor.
     TimerManager *myTimer;
     TimerManager::TimerId myTimerId;
+
+    // It is possible that the timer callback is running even after TimerManager::clear
+    // returns. This id is unique per timer and is used to return from the callback
+    // early in case the time is stale.
+    uInt32 myTimerCallbackId;
 };
 
 #endif // STAGGERED_LOGGER