From 575fb7d77d8f621ab0ffb860902720a330192e26 Mon Sep 17 00:00:00 2001
From: Mark Qvist <bc7291552be7a58f361522990465165c>
Date: Tue, 26 May 2026 13:17:46 +0200
Subject: [PATCH] Prevent LXM persist race in write_to_directory when messages
 change state within very short time spans

---
 LXMF/LXMessage.py | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/LXMF/LXMessage.py b/LXMF/LXMessage.py
index c128c00..a42d1dd 100644
--- a/LXMF/LXMessage.py
+++ b/LXMF/LXMessage.py
@@ -8,6 +8,7 @@ import multiprocessing
 
 import LXMF.LXStamper as LXStamper
 from .LXMF import APP_NAME, compression_support_from_app_data
+from threading import Lock
 
 
 class LXMessage:
@@ -184,6 +185,7 @@ class LXMessage:
         self.__delivery_destination  = None
         self.__delivery_callback     = None
         self.__pn_encrypted_data     = None
+        self.__persist_lock          = Lock()
         self.failed_callback         = None
         
         self.deferred_stamp_generating = False
@@ -674,23 +676,24 @@ class LXMessage:
         file_path = directory_path+"/"+file_name
         tmp_path  = file_path+".tmp."+str(os.getpid() or time.time())
 
-        try:
-            with open(tmp_path, "wb") as file:
-                file.write(self.packed_container())
-                file.flush()
-                try: os.fsync(file.fileno())
-                except OSError as e: RNS.log(f"Error while waiting for persist fsync for {self}: {e}", RNS.LOG_WARNING)
-
-            os.replace(tmp_path, file_path)
-            return file_path
-
-        except Exception as e:
+        with self.__persist_lock:
             try:
-                if os.path.exists(tmp_path): os.unlink(tmp_path)
-            except Exception as e: RNS.log(f"Error while cleaning temporary file {tmp_path} for {self}: {e}", RNS.LOG_ERROR)
+                with open(tmp_path, "wb") as file:
+                    file.write(self.packed_container())
+                    file.flush()
+                    try: os.fsync(file.fileno())
+                    except OSError as e: RNS.log(f"Error while waiting for persist fsync for {self}: {e}", RNS.LOG_WARNING)
 
-            RNS.log(f"Error while writing LXMF message to file \"{file_path}\". The contained exception was: {e}", RNS.LOG_ERROR)
-            return None
+                os.replace(tmp_path, file_path)
+                return file_path
+
+            except Exception as e:
+                try:
+                    if os.path.exists(tmp_path): os.unlink(tmp_path)
+                except Exception as e: RNS.log(f"Error while cleaning temporary file {tmp_path} for {self}: {e}", RNS.LOG_ERROR)
+
+                RNS.log(f"Error while writing LXMF message to file \"{file_path}\". The contained exception was: {e}", RNS.LOG_ERROR)
+                return None
 
     def as_uri(self, finalise=True):
         if not self.packed: