From 6ee42396595feead2929e394cd940ade30487d94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Erik=20Fr=C3=B6jdh?= <erik.frojdh@gmail.com>
Date: Mon, 5 Oct 2026 15:03:35 +0200
Subject: [PATCH] Fix/fifo race (#1591) (#1595)

* fix race condition in Fifo::FreeAddress

(cherry picked from commit dd5b2360d6f55b76eaf9cfdd0a940876bb5d0159)
---
 slsReceiverSoftware/src/Fifo.cpp | 5 ++++-
 slsReceiverSoftware/src/Fifo.h   | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/slsReceiverSoftware/src/Fifo.cpp b/slsReceiverSoftware/src/Fifo.cpp
index 1bec44e12..6740c8ae2 100644
--- a/slsReceiverSoftware/src/Fifo.cpp
+++ b/slsReceiverSoftware/src/Fifo.cpp
@@ -81,7 +81,10 @@ void Fifo::DestroyFifos() {
     fifoStream = nullptr;
 }
 
-void Fifo::FreeAddress(char *&address) { fifoFree->push(address); }
+void Fifo::FreeAddress(char *&address) {
+    std::lock_guard<std::mutex> lock(fifoFreeMutex);
+    fifoFree->push(address);
+}
 
 void Fifo::GetNewAddress(char *&address) {
     int temp = fifoFree->getDataValue();
diff --git a/slsReceiverSoftware/src/Fifo.h b/slsReceiverSoftware/src/Fifo.h
index 729ce368b..fe9f3cf1e 100644
--- a/slsReceiverSoftware/src/Fifo.h
+++ b/slsReceiverSoftware/src/Fifo.h
@@ -16,6 +16,7 @@
 #include "sls/sls_detector_defs.h"
 
 #include <atomic>
+#include <mutex>
 
 namespace sls {
 
@@ -52,6 +53,9 @@ class Fifo : private virtual slsDetectorDefs {
     int fifoDepth;
     std::atomic<int> status_fifoBound;
     std::atomic<int> status_fifoFree;
+    /** fifoFree has several producers, CircularFifo allows only one.
+     * Aligned to avoid false sharing with the members above */
+    alignas(128) std::mutex fifoFreeMutex;
 };
 
 } // namespace sls